8187443: Forest Consolidation: Move files to unified layout

Reviewed-by: darcy, ihse

src/java.base/share/classes/java/util/concurrent/AbstractExecutorService.java

@@ -0,0 +1,312 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent;
+
+import static java.util.concurrent.TimeUnit.NANOSECONDS;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.Iterator;
+import java.util.List;
+
+/**
+ * Provides default implementations of {@link ExecutorService}
+ * execution methods. This class implements the {@code submit},
+ * {@code invokeAny} and {@code invokeAll} methods using a
+ * {@link RunnableFuture} returned by {@code newTaskFor}, which defaults
+ * to the {@link FutureTask} class provided in this package.  For example,
+ * the implementation of {@code submit(Runnable)} creates an
+ * associated {@code RunnableFuture} that is executed and
+ * returned. Subclasses may override the {@code newTaskFor} methods
+ * to return {@code RunnableFuture} implementations other than
+ * {@code FutureTask}.
+ *
+ * <p><b>Extension example</b>. Here is a sketch of a class
+ * that customizes {@link ThreadPoolExecutor} to use
+ * a {@code CustomTask} class instead of the default {@code FutureTask}:
+ * <pre> {@code
+ * public class CustomThreadPoolExecutor extends ThreadPoolExecutor {
+ *
+ *   static class CustomTask<V> implements RunnableFuture<V> {...}
+ *
+ *   protected <V> RunnableFuture<V> newTaskFor(Callable<V> c) {
+ *       return new CustomTask<V>(c);
+ *   }
+ *   protected <V> RunnableFuture<V> newTaskFor(Runnable r, V v) {
+ *       return new CustomTask<V>(r, v);
+ *   }
+ *   // ... add constructors, etc.
+ * }}</pre>
+ *
+ * @since 1.5
+ * @author Doug Lea
+ */
+public abstract class AbstractExecutorService implements ExecutorService {
+
+    /**
+     * Returns a {@code RunnableFuture} for the given runnable and default
+     * value.
+     *
+     * @param runnable the runnable task being wrapped
+     * @param value the default value for the returned future
+     * @param <T> the type of the given value
+     * @return a {@code RunnableFuture} which, when run, will run the
+     * underlying runnable and which, as a {@code Future}, will yield
+     * the given value as its result and provide for cancellation of
+     * the underlying task
+     * @since 1.6
+     */
+    protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) {
+        return new FutureTask<T>(runnable, value);
+    }
+
+    /**
+     * Returns a {@code RunnableFuture} for the given callable task.
+     *
+     * @param callable the callable task being wrapped
+     * @param <T> the type of the callable's result
+     * @return a {@code RunnableFuture} which, when run, will call the
+     * underlying callable and which, as a {@code Future}, will yield
+     * the callable's result as its result and provide for
+     * cancellation of the underlying task
+     * @since 1.6
+     */
+    protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
+        return new FutureTask<T>(callable);
+    }
+
+    /**
+     * @throws RejectedExecutionException {@inheritDoc}
+     * @throws NullPointerException       {@inheritDoc}
+     */
+    public Future<?> submit(Runnable task) {
+        if (task == null) throw new NullPointerException();
+        RunnableFuture<Void> ftask = newTaskFor(task, null);
+        execute(ftask);
+        return ftask;
+    }
+
+    /**
+     * @throws RejectedExecutionException {@inheritDoc}
+     * @throws NullPointerException       {@inheritDoc}
+     */
+    public <T> Future<T> submit(Runnable task, T result) {
+        if (task == null) throw new NullPointerException();
+        RunnableFuture<T> ftask = newTaskFor(task, result);
+        execute(ftask);
+        return ftask;
+    }
+
+    /**
+     * @throws RejectedExecutionException {@inheritDoc}
+     * @throws NullPointerException       {@inheritDoc}
+     */
+    public <T> Future<T> submit(Callable<T> task) {
+        if (task == null) throw new NullPointerException();
+        RunnableFuture<T> ftask = newTaskFor(task);
+        execute(ftask);
+        return ftask;
+    }
+
+    /**
+     * the main mechanics of invokeAny.
+     */
+    private <T> T doInvokeAny(Collection<? extends Callable<T>> tasks,
+                              boolean timed, long nanos)
+        throws InterruptedException, ExecutionException, TimeoutException {
+        if (tasks == null)
+            throw new NullPointerException();
+        int ntasks = tasks.size();
+        if (ntasks == 0)
+            throw new IllegalArgumentException();
+        ArrayList<Future<T>> futures = new ArrayList<>(ntasks);
+        ExecutorCompletionService<T> ecs =
+            new ExecutorCompletionService<T>(this);
+
+        // For efficiency, especially in executors with limited
+        // parallelism, check to see if previously submitted tasks are
+        // done before submitting more of them. This interleaving
+        // plus the exception mechanics account for messiness of main
+        // loop.
+
+        try {
+            // Record exceptions so that if we fail to obtain any
+            // result, we can throw the last exception we got.
+            ExecutionException ee = null;
+            final long deadline = timed ? System.nanoTime() + nanos : 0L;
+            Iterator<? extends Callable<T>> it = tasks.iterator();
+
+            // Start one task for sure; the rest incrementally
+            futures.add(ecs.submit(it.next()));
+            --ntasks;
+            int active = 1;
+
+            for (;;) {
+                Future<T> f = ecs.poll();
+                if (f == null) {
+                    if (ntasks > 0) {
+                        --ntasks;
+                        futures.add(ecs.submit(it.next()));
+                        ++active;
+                    }
+                    else if (active == 0)
+                        break;
+                    else if (timed) {
+                        f = ecs.poll(nanos, NANOSECONDS);
+                        if (f == null)
+                            throw new TimeoutException();
+                        nanos = deadline - System.nanoTime();
+                    }
+                    else
+                        f = ecs.take();
+                }
+                if (f != null) {
+                    --active;
+                    try {
+                        return f.get();
+                    } catch (ExecutionException eex) {
+                        ee = eex;
+                    } catch (RuntimeException rex) {
+                        ee = new ExecutionException(rex);
+                    }
+                }
+            }
+
+            if (ee == null)
+                ee = new ExecutionException();
+            throw ee;
+
+        } finally {
+            cancelAll(futures);
+        }
+    }
+
+    public <T> T invokeAny(Collection<? extends Callable<T>> tasks)
+        throws InterruptedException, ExecutionException {
+        try {
+            return doInvokeAny(tasks, false, 0);
+        } catch (TimeoutException cannotHappen) {
+            assert false;
+            return null;
+        }
+    }
+
+    public <T> T invokeAny(Collection<? extends Callable<T>> tasks,
+                           long timeout, TimeUnit unit)
+        throws InterruptedException, ExecutionException, TimeoutException {
+        return doInvokeAny(tasks, true, unit.toNanos(timeout));
+    }
+
+    public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks)
+        throws InterruptedException {
+        if (tasks == null)
+            throw new NullPointerException();
+        ArrayList<Future<T>> futures = new ArrayList<>(tasks.size());
+        try {
+            for (Callable<T> t : tasks) {
+                RunnableFuture<T> f = newTaskFor(t);
+                futures.add(f);
+                execute(f);
+            }
+            for (int i = 0, size = futures.size(); i < size; i++) {
+                Future<T> f = futures.get(i);
+                if (!f.isDone()) {
+                    try { f.get(); }
+                    catch (CancellationException ignore) {}
+                    catch (ExecutionException ignore) {}
+                }
+            }
+            return futures;
+        } catch (Throwable t) {
+            cancelAll(futures);
+            throw t;
+        }
+    }
+
+    public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks,
+                                         long timeout, TimeUnit unit)
+        throws InterruptedException {
+        if (tasks == null)
+            throw new NullPointerException();
+        final long nanos = unit.toNanos(timeout);
+        final long deadline = System.nanoTime() + nanos;
+        ArrayList<Future<T>> futures = new ArrayList<>(tasks.size());
+        int j = 0;
+        timedOut: try {
+            for (Callable<T> t : tasks)
+                futures.add(newTaskFor(t));
+
+            final int size = futures.size();
+
+            // Interleave time checks and calls to execute in case
+            // executor doesn't have any/much parallelism.
+            for (int i = 0; i < size; i++) {
+                if (((i == 0) ? nanos : deadline - System.nanoTime()) <= 0L)
+                    break timedOut;
+                execute((Runnable)futures.get(i));
+            }
+
+            for (; j < size; j++) {
+                Future<T> f = futures.get(j);
+                if (!f.isDone()) {
+                    try { f.get(deadline - System.nanoTime(), NANOSECONDS); }
+                    catch (CancellationException ignore) {}
+                    catch (ExecutionException ignore) {}
+                    catch (TimeoutException timedOut) {
+                        break timedOut;
+                    }
+                }
+            }
+            return futures;
+        } catch (Throwable t) {
+            cancelAll(futures);
+            throw t;
+        }
+        // Timed out before all the tasks could be completed; cancel remaining
+        cancelAll(futures, j);
+        return futures;
+    }
+
+    private static <T> void cancelAll(ArrayList<Future<T>> futures) {
+        cancelAll(futures, 0);
+    }
+
+    /** Cancels all futures with index at least j. */
+    private static <T> void cancelAll(ArrayList<Future<T>> futures, int j) {
+        for (int size = futures.size(); j < size; j++)
+            futures.get(j).cancel(true);
+    }
+}

src/java.base/share/classes/java/util/concurrent/BlockingDeque.java

@@ -0,0 +1,649 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent;
+
+import java.util.Deque;
+import java.util.Iterator;
+import java.util.NoSuchElementException;
+
+/**
+ * A {@link Deque} that additionally supports blocking operations that wait
+ * for the deque to become non-empty when retrieving an element, and wait for
+ * space to become available in the deque when storing an element.
+ *
+ * <p>{@code BlockingDeque} methods come in four forms, with different ways
+ * of handling operations that cannot be satisfied immediately, but may be
+ * satisfied at some point in the future:
+ * one throws an exception, the second returns a special value (either
+ * {@code null} or {@code false}, depending on the operation), the third
+ * blocks the current thread indefinitely until the operation can succeed,
+ * and the fourth blocks for only a given maximum time limit before giving
+ * up.  These methods are summarized in the following table:
+ *
+ * <table class="plain">
+ * <caption>Summary of BlockingDeque methods</caption>
+ *  <tr>
+ *    <th id="First" colspan="5"> First Element (Head)</th>
+ *  </tr>
+ *  <tr>
+ *    <td></td>
+ *    <th id="FThrow" style="font-weight:normal; font-style: italic">Throws exception</th>
+ *    <th id="FValue" style="font-weight:normal; font-style: italic">Special value</th>
+ *    <th id="FBlock" style="font-weight:normal; font-style: italic">Blocks</th>
+ *    <th id="FTimes" style="font-weight:normal; font-style: italic">Times out</th>
+ *  </tr>
+ *  <tr>
+ *    <th id="FInsert" style="text-align:left">Insert</th>
+ *    <td headers="First FInsert FThrow">{@link #addFirst(Object) addFirst(e)}</td>
+ *    <td headers="First FInsert FValue">{@link #offerFirst(Object) offerFirst(e)}</td>
+ *    <td headers="First FInsert FBlock">{@link #putFirst(Object) putFirst(e)}</td>
+ *    <td headers="First FInsert FTimes">{@link #offerFirst(Object, long, TimeUnit) offerFirst(e, time, unit)}</td>
+ *  </tr>
+ *  <tr>
+ *    <th id="FRemove" style="text-align:left">Remove</th>
+ *    <td headers="First FRemove FThrow">{@link #removeFirst() removeFirst()}</td>
+ *    <td headers="First FRemove FValue">{@link #pollFirst() pollFirst()}</td>
+ *    <td headers="First FRemove FBlock">{@link #takeFirst() takeFirst()}</td>
+ *    <td headers="First FRemove FTimes">{@link #pollFirst(long, TimeUnit) pollFirst(time, unit)}</td>
+ *  </tr>
+ *  <tr>
+ *    <th id="FExamine" style="text-align:left">Examine</th>
+ *    <td headers="First FExamine FThrow">{@link #getFirst() getFirst()}</td>
+ *    <td headers="First FExamine FValue">{@link #peekFirst() peekFirst()}</td>
+ *    <td headers="First FExamine FBlock" style="font-style:italic">not applicable</td>
+ *    <td headers="First FExamine FTimes" style="font-style:italic">not applicable</td>
+ *  </tr>
+ *  <tr>
+ *    <th id="Last" colspan="5"> Last Element (Tail)</th>
+ *  </tr>
+ *  <tr>
+ *    <td></td>
+ *    <th id="LThrow" style="font-weight:normal; font-style: italic">Throws exception</th>
+ *    <th id="LValue" style="font-weight:normal; font-style: italic">Special value</th>
+ *    <th id="LBlock" style="font-weight:normal; font-style: italic">Blocks</th>
+ *    <th id="LTimes" style="font-weight:normal; font-style: italic">Times out</th>
+ *  </tr>
+ *  <tr>
+ *    <th id="LInsert" style="text-align:left">Insert</th>
+ *    <td headers="Last LInsert LThrow">{@link #addLast(Object) addLast(e)}</td>
+ *    <td headers="Last LInsert LValue">{@link #offerLast(Object) offerLast(e)}</td>
+ *    <td headers="Last LInsert LBlock">{@link #putLast(Object) putLast(e)}</td>
+ *    <td headers="Last LInsert LTimes">{@link #offerLast(Object, long, TimeUnit) offerLast(e, time, unit)}</td>
+ *  </tr>
+ *  <tr>
+ *    <th id="LRemove" style="text-align:left">Remove</th>
+ *    <td headers="Last LRemove LThrow">{@link #removeLast() removeLast()}</td>
+ *    <td headers="Last LRemove LValue">{@link #pollLast() pollLast()}</td>
+ *    <td headers="Last LRemove LBlock">{@link #takeLast() takeLast()}</td>
+ *    <td headers="Last LRemove LTimes">{@link #pollLast(long, TimeUnit) pollLast(time, unit)}</td>
+ *  </tr>
+ *  <tr>
+ *    <th id="LExamine" style="text-align:left">Examine</th>
+ *    <td headers="Last LExamine LThrow">{@link #getLast() getLast()}</td>
+ *    <td headers="Last LExamine LValue">{@link #peekLast() peekLast()}</td>
+ *    <td headers="Last LExamine LBlock" style="font-style:italic">not applicable</td>
+ *    <td headers="Last LExamine LTimes" style="font-style:italic">not applicable</td>
+ *  </tr>
+ * </table>
+ *
+ * <p>Like any {@link BlockingQueue}, a {@code BlockingDeque} is thread safe,
+ * does not permit null elements, and may (or may not) be
+ * capacity-constrained.
+ *
+ * <p>A {@code BlockingDeque} implementation may be used directly as a FIFO
+ * {@code BlockingQueue}. The methods inherited from the
+ * {@code BlockingQueue} interface are precisely equivalent to
+ * {@code BlockingDeque} methods as indicated in the following table:
+ *
+ * <table class="plain">
+ * <caption>Comparison of BlockingQueue and BlockingDeque methods</caption>
+ *  <tr>
+ *    <td></td>
+ *    <th id="BQueue"> {@code BlockingQueue} Method</th>
+ *    <th id="BDeque"> Equivalent {@code BlockingDeque} Method</th>
+ *  </tr>
+ *  <tr>
+ *    <th id="Insert" rowspan="4" style="text-align:left; vertical-align:top">Insert</th>
+ *    <th id="add" style="font-weight:normal; text-align:left">{@link #add(Object) add(e)}</th>
+ *    <td headers="Insert BDeque add">{@link #addLast(Object) addLast(e)}</td>
+ *  </tr>
+ *  <tr>
+ *    <th id="offer1" style="font-weight:normal; text-align:left">{@link #offer(Object) offer(e)}</th>
+ *    <td headers="Insert BDeque offer1">{@link #offerLast(Object) offerLast(e)}</td>
+ *  </tr>
+ *  <tr>
+ *    <th id="put" style="font-weight:normal; text-align:left">{@link #put(Object) put(e)}</th>
+ *    <td headers="Insert BDeque put">{@link #putLast(Object) putLast(e)}</td>
+ *  </tr>
+ *  <tr>
+ *    <th id="offer2" style="font-weight:normal; text-align:left">{@link #offer(Object, long, TimeUnit) offer(e, time, unit)}</th>
+ *    <td headers="Insert BDeque offer2">{@link #offerLast(Object, long, TimeUnit) offerLast(e, time, unit)}</td>
+ *  </tr>
+ *  <tr>
+ *    <th id="Remove" rowspan="4" style="text-align:left; vertical-align:top">Remove</th>
+ *    <th id="remove" style="font-weight:normal; text-align:left">{@link #remove() remove()}</th>
+ *    <td headers="Remove BDeque remove">{@link #removeFirst() removeFirst()}</td>
+ *  </tr>
+ *  <tr>
+ *    <th id="poll1" style="font-weight:normal; text-align:left">{@link #poll() poll()}</th>
+ *    <td headers="Remove BDeque poll1">{@link #pollFirst() pollFirst()}</td>
+ *  </tr>
+ *  <tr>
+ *    <th id="take" style="font-weight:normal; text-align:left">{@link #take() take()}</th>
+ *    <td headers="Remove BDeque take">{@link #takeFirst() takeFirst()}</td>
+ *  </tr>
+ *  <tr>
+ *    <th id="poll2" style="font-weight:normal; text-align:left">{@link #poll(long, TimeUnit) poll(time, unit)}</th>
+ *    <td headers="Remove BDeque poll2">{@link #pollFirst(long, TimeUnit) pollFirst(time, unit)}</td>
+ *  </tr>
+ *  <tr>
+ *    <th id="Examine" rowspan="2" style="text-align:left; vertical-align:top">Examine</th>
+ *    <th id="element" style="font-weight:normal; text-align:left">{@link #element() element()}</th>
+ *    <td headers="Examine BDeque element">{@link #getFirst() getFirst()}</td>
+ *  </tr>
+ *  <tr>
+ *    <th id="peek" style="font-weight:normal; text-align:left">{@link #peek() peek()}</th>
+ *    <td headers="Examine BDeque peek">{@link #peekFirst() peekFirst()}</td>
+ *  </tr>
+ * </table>
+ *
+ * <p>Memory consistency effects: As with other concurrent
+ * collections, actions in a thread prior to placing an object into a
+ * {@code BlockingDeque}
+ * <a href="package-summary.html#MemoryVisibility"><i>happen-before</i></a>
+ * actions subsequent to the access or removal of that element from
+ * the {@code BlockingDeque} in another thread.
+ *
+ * <p>This interface is a member of the
+ * <a href="{@docRoot}/java/util/package-summary.html#CollectionsFramework">
+ * Java Collections Framework</a>.
+ *
+ * @since 1.6
+ * @author Doug Lea
+ * @param <E> the type of elements held in this deque
+ */
+public interface BlockingDeque<E> extends BlockingQueue<E>, Deque<E> {
+    /*
+     * We have "diamond" multiple interface inheritance here, and that
+     * introduces ambiguities.  Methods might end up with different
+     * specs depending on the branch chosen by javadoc.  Thus a lot of
+     * methods specs here are copied from superinterfaces.
+     */
+
+    /**
+     * Inserts the specified element at the front of this deque if it is
+     * possible to do so immediately without violating capacity restrictions,
+     * throwing an {@code IllegalStateException} if no space is currently
+     * available.  When using a capacity-restricted deque, it is generally
+     * preferable to use {@link #offerFirst(Object) offerFirst}.
+     *
+     * @param e the element to add
+     * @throws IllegalStateException {@inheritDoc}
+     * @throws ClassCastException {@inheritDoc}
+     * @throws NullPointerException if the specified element is null
+     * @throws IllegalArgumentException {@inheritDoc}
+     */
+    void addFirst(E e);
+
+    /**
+     * Inserts the specified element at the end of this deque if it is
+     * possible to do so immediately without violating capacity restrictions,
+     * throwing an {@code IllegalStateException} if no space is currently
+     * available.  When using a capacity-restricted deque, it is generally
+     * preferable to use {@link #offerLast(Object) offerLast}.
+     *
+     * @param e the element to add
+     * @throws IllegalStateException {@inheritDoc}
+     * @throws ClassCastException {@inheritDoc}
+     * @throws NullPointerException if the specified element is null
+     * @throws IllegalArgumentException {@inheritDoc}
+     */
+    void addLast(E e);
+
+    /**
+     * Inserts the specified element at the front of this deque if it is
+     * possible to do so immediately without violating capacity restrictions,
+     * returning {@code true} upon success and {@code false} if no space is
+     * currently available.
+     * When using a capacity-restricted deque, this method is generally
+     * preferable to the {@link #addFirst(Object) addFirst} method, which can
+     * fail to insert an element only by throwing an exception.
+     *
+     * @param e the element to add
+     * @throws ClassCastException {@inheritDoc}
+     * @throws NullPointerException if the specified element is null
+     * @throws IllegalArgumentException {@inheritDoc}
+     */
+    boolean offerFirst(E e);
+
+    /**
+     * Inserts the specified element at the end of this deque if it is
+     * possible to do so immediately without violating capacity restrictions,
+     * returning {@code true} upon success and {@code false} if no space is
+     * currently available.
+     * When using a capacity-restricted deque, this method is generally
+     * preferable to the {@link #addLast(Object) addLast} method, which can
+     * fail to insert an element only by throwing an exception.
+     *
+     * @param e the element to add
+     * @throws ClassCastException {@inheritDoc}
+     * @throws NullPointerException if the specified element is null
+     * @throws IllegalArgumentException {@inheritDoc}
+     */
+    boolean offerLast(E e);
+
+    /**
+     * Inserts the specified element at the front of this deque,
+     * waiting if necessary for space to become available.
+     *
+     * @param e the element to add
+     * @throws InterruptedException if interrupted while waiting
+     * @throws ClassCastException if the class of the specified element
+     *         prevents it from being added to this deque
+     * @throws NullPointerException if the specified element is null
+     * @throws IllegalArgumentException if some property of the specified
+     *         element prevents it from being added to this deque
+     */
+    void putFirst(E e) throws InterruptedException;
+
+    /**
+     * Inserts the specified element at the end of this deque,
+     * waiting if necessary for space to become available.
+     *
+     * @param e the element to add
+     * @throws InterruptedException if interrupted while waiting
+     * @throws ClassCastException if the class of the specified element
+     *         prevents it from being added to this deque
+     * @throws NullPointerException if the specified element is null
+     * @throws IllegalArgumentException if some property of the specified
+     *         element prevents it from being added to this deque
+     */
+    void putLast(E e) throws InterruptedException;
+
+    /**
+     * Inserts the specified element at the front of this deque,
+     * waiting up to the specified wait time if necessary for space to
+     * become available.
+     *
+     * @param e the element to add
+     * @param timeout how long to wait before giving up, in units of
+     *        {@code unit}
+     * @param unit a {@code TimeUnit} determining how to interpret the
+     *        {@code timeout} parameter
+     * @return {@code true} if successful, or {@code false} if
+     *         the specified waiting time elapses before space is available
+     * @throws InterruptedException if interrupted while waiting
+     * @throws ClassCastException if the class of the specified element
+     *         prevents it from being added to this deque
+     * @throws NullPointerException if the specified element is null
+     * @throws IllegalArgumentException if some property of the specified
+     *         element prevents it from being added to this deque
+     */
+    boolean offerFirst(E e, long timeout, TimeUnit unit)
+        throws InterruptedException;
+
+    /**
+     * Inserts the specified element at the end of this deque,
+     * waiting up to the specified wait time if necessary for space to
+     * become available.
+     *
+     * @param e the element to add
+     * @param timeout how long to wait before giving up, in units of
+     *        {@code unit}
+     * @param unit a {@code TimeUnit} determining how to interpret the
+     *        {@code timeout} parameter
+     * @return {@code true} if successful, or {@code false} if
+     *         the specified waiting time elapses before space is available
+     * @throws InterruptedException if interrupted while waiting
+     * @throws ClassCastException if the class of the specified element
+     *         prevents it from being added to this deque
+     * @throws NullPointerException if the specified element is null
+     * @throws IllegalArgumentException if some property of the specified
+     *         element prevents it from being added to this deque
+     */
+    boolean offerLast(E e, long timeout, TimeUnit unit)
+        throws InterruptedException;
+
+    /**
+     * Retrieves and removes the first element of this deque, waiting
+     * if necessary until an element becomes available.
+     *
+     * @return the head of this deque
+     * @throws InterruptedException if interrupted while waiting
+     */
+    E takeFirst() throws InterruptedException;
+
+    /**
+     * Retrieves and removes the last element of this deque, waiting
+     * if necessary until an element becomes available.
+     *
+     * @return the tail of this deque
+     * @throws InterruptedException if interrupted while waiting
+     */
+    E takeLast() throws InterruptedException;
+
+    /**
+     * Retrieves and removes the first element of this deque, waiting
+     * up to the specified wait time if necessary for an element to
+     * become available.
+     *
+     * @param timeout how long to wait before giving up, in units of
+     *        {@code unit}
+     * @param unit a {@code TimeUnit} determining how to interpret the
+     *        {@code timeout} parameter
+     * @return the head of this deque, or {@code null} if the specified
+     *         waiting time elapses before an element is available
+     * @throws InterruptedException if interrupted while waiting
+     */
+    E pollFirst(long timeout, TimeUnit unit)
+        throws InterruptedException;
+
+    /**
+     * Retrieves and removes the last element of this deque, waiting
+     * up to the specified wait time if necessary for an element to
+     * become available.
+     *
+     * @param timeout how long to wait before giving up, in units of
+     *        {@code unit}
+     * @param unit a {@code TimeUnit} determining how to interpret the
+     *        {@code timeout} parameter
+     * @return the tail of this deque, or {@code null} if the specified
+     *         waiting time elapses before an element is available
+     * @throws InterruptedException if interrupted while waiting
+     */
+    E pollLast(long timeout, TimeUnit unit)
+        throws InterruptedException;
+
+    /**
+     * Removes the first occurrence of the specified element from this deque.
+     * If the deque does not contain the element, it is unchanged.
+     * More formally, removes the first element {@code e} such that
+     * {@code o.equals(e)} (if such an element exists).
+     * Returns {@code true} if this deque contained the specified element
+     * (or equivalently, if this deque changed as a result of the call).
+     *
+     * @param o element to be removed from this deque, if present
+     * @return {@code true} if an element was removed as a result of this call
+     * @throws ClassCastException if the class of the specified element
+     *         is incompatible with this deque
+     * (<a href="{@docRoot}/java/util/Collection.html#optional-restrictions">optional</a>)
+     * @throws NullPointerException if the specified element is null
+     * (<a href="{@docRoot}/java/util/Collection.html#optional-restrictions">optional</a>)
+     */
+    boolean removeFirstOccurrence(Object o);
+
+    /**
+     * Removes the last occurrence of the specified element from this deque.
+     * If the deque does not contain the element, it is unchanged.
+     * More formally, removes the last element {@code e} such that
+     * {@code o.equals(e)} (if such an element exists).
+     * Returns {@code true} if this deque contained the specified element
+     * (or equivalently, if this deque changed as a result of the call).
+     *
+     * @param o element to be removed from this deque, if present
+     * @return {@code true} if an element was removed as a result of this call
+     * @throws ClassCastException if the class of the specified element
+     *         is incompatible with this deque
+     * (<a href="{@docRoot}/java/util/Collection.html#optional-restrictions">optional</a>)
+     * @throws NullPointerException if the specified element is null
+     * (<a href="{@docRoot}/java/util/Collection.html#optional-restrictions">optional</a>)
+     */
+    boolean removeLastOccurrence(Object o);
+
+    // *** BlockingQueue methods ***
+
+    /**
+     * Inserts the specified element into the queue represented by this deque
+     * (in other words, at the tail of this deque) if it is possible to do so
+     * immediately without violating capacity restrictions, returning
+     * {@code true} upon success and throwing an
+     * {@code IllegalStateException} if no space is currently available.
+     * When using a capacity-restricted deque, it is generally preferable to
+     * use {@link #offer(Object) offer}.
+     *
+     * <p>This method is equivalent to {@link #addLast(Object) addLast}.
+     *
+     * @param e the element to add
+     * @throws IllegalStateException {@inheritDoc}
+     * @throws ClassCastException if the class of the specified element
+     *         prevents it from being added to this deque
+     * @throws NullPointerException if the specified element is null
+     * @throws IllegalArgumentException if some property of the specified
+     *         element prevents it from being added to this deque
+     */
+    boolean add(E e);
+
+    /**
+     * Inserts the specified element into the queue represented by this deque
+     * (in other words, at the tail of this deque) if it is possible to do so
+     * immediately without violating capacity restrictions, returning
+     * {@code true} upon success and {@code false} if no space is currently
+     * available.  When using a capacity-restricted deque, this method is
+     * generally preferable to the {@link #add} method, which can fail to
+     * insert an element only by throwing an exception.
+     *
+     * <p>This method is equivalent to {@link #offerLast(Object) offerLast}.
+     *
+     * @param e the element to add
+     * @throws ClassCastException if the class of the specified element
+     *         prevents it from being added to this deque
+     * @throws NullPointerException if the specified element is null
+     * @throws IllegalArgumentException if some property of the specified
+     *         element prevents it from being added to this deque
+     */
+    boolean offer(E e);
+
+    /**
+     * Inserts the specified element into the queue represented by this deque
+     * (in other words, at the tail of this deque), waiting if necessary for
+     * space to become available.
+     *
+     * <p>This method is equivalent to {@link #putLast(Object) putLast}.
+     *
+     * @param e the element to add
+     * @throws InterruptedException {@inheritDoc}
+     * @throws ClassCastException if the class of the specified element
+     *         prevents it from being added to this deque
+     * @throws NullPointerException if the specified element is null
+     * @throws IllegalArgumentException if some property of the specified
+     *         element prevents it from being added to this deque
+     */
+    void put(E e) throws InterruptedException;
+
+    /**
+     * Inserts the specified element into the queue represented by this deque
+     * (in other words, at the tail of this deque), waiting up to the
+     * specified wait time if necessary for space to become available.
+     *
+     * <p>This method is equivalent to
+     * {@link #offerLast(Object,long,TimeUnit) offerLast}.
+     *
+     * @param e the element to add
+     * @return {@code true} if the element was added to this deque, else
+     *         {@code false}
+     * @throws InterruptedException {@inheritDoc}
+     * @throws ClassCastException if the class of the specified element
+     *         prevents it from being added to this deque
+     * @throws NullPointerException if the specified element is null
+     * @throws IllegalArgumentException if some property of the specified
+     *         element prevents it from being added to this deque
+     */
+    boolean offer(E e, long timeout, TimeUnit unit)
+        throws InterruptedException;
+
+    /**
+     * Retrieves and removes the head of the queue represented by this deque
+     * (in other words, the first element of this deque).
+     * This method differs from {@link #poll() poll()} only in that it
+     * throws an exception if this deque is empty.
+     *
+     * <p>This method is equivalent to {@link #removeFirst() removeFirst}.
+     *
+     * @return the head of the queue represented by this deque
+     * @throws NoSuchElementException if this deque is empty
+     */
+    E remove();
+
+    /**
+     * Retrieves and removes the head of the queue represented by this deque
+     * (in other words, the first element of this deque), or returns
+     * {@code null} if this deque is empty.
+     *
+     * <p>This method is equivalent to {@link #pollFirst()}.
+     *
+     * @return the head of this deque, or {@code null} if this deque is empty
+     */
+    E poll();
+
+    /**
+     * Retrieves and removes the head of the queue represented by this deque
+     * (in other words, the first element of this deque), waiting if
+     * necessary until an element becomes available.
+     *
+     * <p>This method is equivalent to {@link #takeFirst() takeFirst}.
+     *
+     * @return the head of this deque
+     * @throws InterruptedException if interrupted while waiting
+     */
+    E take() throws InterruptedException;
+
+    /**
+     * Retrieves and removes the head of the queue represented by this deque
+     * (in other words, the first element of this deque), waiting up to the
+     * specified wait time if necessary for an element to become available.
+     *
+     * <p>This method is equivalent to
+     * {@link #pollFirst(long,TimeUnit) pollFirst}.
+     *
+     * @return the head of this deque, or {@code null} if the
+     *         specified waiting time elapses before an element is available
+     * @throws InterruptedException if interrupted while waiting
+     */
+    E poll(long timeout, TimeUnit unit)
+        throws InterruptedException;
+
+    /**
+     * Retrieves, but does not remove, the head of the queue represented by
+     * this deque (in other words, the first element of this deque).
+     * This method differs from {@link #peek() peek} only in that it throws an
+     * exception if this deque is empty.
+     *
+     * <p>This method is equivalent to {@link #getFirst() getFirst}.
+     *
+     * @return the head of this deque
+     * @throws NoSuchElementException if this deque is empty
+     */
+    E element();
+
+    /**
+     * Retrieves, but does not remove, the head of the queue represented by
+     * this deque (in other words, the first element of this deque), or
+     * returns {@code null} if this deque is empty.
+     *
+     * <p>This method is equivalent to {@link #peekFirst() peekFirst}.
+     *
+     * @return the head of this deque, or {@code null} if this deque is empty
+     */
+    E peek();
+
+    /**
+     * Removes the first occurrence of the specified element from this deque.
+     * If the deque does not contain the element, it is unchanged.
+     * More formally, removes the first element {@code e} such that
+     * {@code o.equals(e)} (if such an element exists).
+     * Returns {@code true} if this deque contained the specified element
+     * (or equivalently, if this deque changed as a result of the call).
+     *
+     * <p>This method is equivalent to
+     * {@link #removeFirstOccurrence(Object) removeFirstOccurrence}.
+     *
+     * @param o element to be removed from this deque, if present
+     * @return {@code true} if this deque changed as a result of the call
+     * @throws ClassCastException if the class of the specified element
+     *         is incompatible with this deque
+     * (<a href="{@docRoot}/java/util/Collection.html#optional-restrictions">optional</a>)
+     * @throws NullPointerException if the specified element is null
+     * (<a href="{@docRoot}/java/util/Collection.html#optional-restrictions">optional</a>)
+     */
+    boolean remove(Object o);
+
+    /**
+     * Returns {@code true} if this deque contains the specified element.
+     * More formally, returns {@code true} if and only if this deque contains
+     * at least one element {@code e} such that {@code o.equals(e)}.
+     *
+     * @param o object to be checked for containment in this deque
+     * @return {@code true} if this deque contains the specified element
+     * @throws ClassCastException if the class of the specified element
+     *         is incompatible with this deque
+     * (<a href="{@docRoot}/java/util/Collection.html#optional-restrictions">optional</a>)
+     * @throws NullPointerException if the specified element is null
+     * (<a href="{@docRoot}/java/util/Collection.html#optional-restrictions">optional</a>)
+     */
+    boolean contains(Object o);
+
+    /**
+     * Returns the number of elements in this deque.
+     *
+     * @return the number of elements in this deque
+     */
+    int size();
+
+    /**
+     * Returns an iterator over the elements in this deque in proper sequence.
+     * The elements will be returned in order from first (head) to last (tail).
+     *
+     * @return an iterator over the elements in this deque in proper sequence
+     */
+    Iterator<E> iterator();
+
+    // *** Stack methods ***
+
+    /**
+     * Pushes an element onto the stack represented by this deque (in other
+     * words, at the head of this deque) if it is possible to do so
+     * immediately without violating capacity restrictions, throwing an
+     * {@code IllegalStateException} if no space is currently available.
+     *
+     * <p>This method is equivalent to {@link #addFirst(Object) addFirst}.
+     *
+     * @throws IllegalStateException {@inheritDoc}
+     * @throws ClassCastException {@inheritDoc}
+     * @throws NullPointerException if the specified element is null
+     * @throws IllegalArgumentException {@inheritDoc}
+     */
+    void push(E e);
+}

src/java.base/share/classes/java/util/concurrent/BlockingQueue.java

@@ -0,0 +1,375 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent;
+
+import java.util.Collection;
+import java.util.Queue;
+
+/**
+ * A {@link Queue} that additionally supports operations that wait for
+ * the queue to become non-empty when retrieving an element, and wait
+ * for space to become available in the queue when storing an element.
+ *
+ * <p>{@code BlockingQueue} methods come in four forms, with different ways
+ * of handling operations that cannot be satisfied immediately, but may be
+ * satisfied at some point in the future:
+ * one throws an exception, the second returns a special value (either
+ * {@code null} or {@code false}, depending on the operation), the third
+ * blocks the current thread indefinitely until the operation can succeed,
+ * and the fourth blocks for only a given maximum time limit before giving
+ * up.  These methods are summarized in the following table:
+ *
+ * <table class="plain">
+ * <caption>Summary of BlockingQueue methods</caption>
+ *  <tr>
+ *    <td></td>
+ *    <th scope="col" style="font-weight:normal; font-style:italic">Throws exception</th>
+ *    <th scope="col" style="font-weight:normal; font-style:italic">Special value</th>
+ *    <th scope="col" style="font-weight:normal; font-style:italic">Blocks</th>
+ *    <th scope="col" style="font-weight:normal; font-style:italic">Times out</th>
+ *  </tr>
+ *  <tr>
+ *    <th scope="row" style="text-align:left">Insert</th>
+ *    <td>{@link #add(Object) add(e)}</td>
+ *    <td>{@link #offer(Object) offer(e)}</td>
+ *    <td>{@link #put(Object) put(e)}</td>
+ *    <td>{@link #offer(Object, long, TimeUnit) offer(e, time, unit)}</td>
+ *  </tr>
+ *  <tr>
+ *    <th scope="row" style="text-align:left">Remove</th>
+ *    <td>{@link #remove() remove()}</td>
+ *    <td>{@link #poll() poll()}</td>
+ *    <td>{@link #take() take()}</td>
+ *    <td>{@link #poll(long, TimeUnit) poll(time, unit)}</td>
+ *  </tr>
+ *  <tr>
+ *    <th scope="row" style="text-align:left">Examine</th>
+ *    <td>{@link #element() element()}</td>
+ *    <td>{@link #peek() peek()}</td>
+ *    <td style="font-style: italic">not applicable</td>
+ *    <td style="font-style: italic">not applicable</td>
+ *  </tr>
+ * </table>
+ *
+ * <p>A {@code BlockingQueue} does not accept {@code null} elements.
+ * Implementations throw {@code NullPointerException} on attempts
+ * to {@code add}, {@code put} or {@code offer} a {@code null}.  A
+ * {@code null} is used as a sentinel value to indicate failure of
+ * {@code poll} operations.
+ *
+ * <p>A {@code BlockingQueue} may be capacity bounded. At any given
+ * time it may have a {@code remainingCapacity} beyond which no
+ * additional elements can be {@code put} without blocking.
+ * A {@code BlockingQueue} without any intrinsic capacity constraints always
+ * reports a remaining capacity of {@code Integer.MAX_VALUE}.
+ *
+ * <p>{@code BlockingQueue} implementations are designed to be used
+ * primarily for producer-consumer queues, but additionally support
+ * the {@link Collection} interface.  So, for example, it is
+ * possible to remove an arbitrary element from a queue using
+ * {@code remove(x)}. However, such operations are in general
+ * <em>not</em> performed very efficiently, and are intended for only
+ * occasional use, such as when a queued message is cancelled.
+ *
+ * <p>{@code BlockingQueue} implementations are thread-safe.  All
+ * queuing methods achieve their effects atomically using internal
+ * locks or other forms of concurrency control. However, the
+ * <em>bulk</em> Collection operations {@code addAll},
+ * {@code containsAll}, {@code retainAll} and {@code removeAll} are
+ * <em>not</em> necessarily performed atomically unless specified
+ * otherwise in an implementation. So it is possible, for example, for
+ * {@code addAll(c)} to fail (throwing an exception) after adding
+ * only some of the elements in {@code c}.
+ *
+ * <p>A {@code BlockingQueue} does <em>not</em> intrinsically support
+ * any kind of &quot;close&quot; or &quot;shutdown&quot; operation to
+ * indicate that no more items will be added.  The needs and usage of
+ * such features tend to be implementation-dependent. For example, a
+ * common tactic is for producers to insert special
+ * <em>end-of-stream</em> or <em>poison</em> objects, that are
+ * interpreted accordingly when taken by consumers.
+ *
+ * <p>
+ * Usage example, based on a typical producer-consumer scenario.
+ * Note that a {@code BlockingQueue} can safely be used with multiple
+ * producers and multiple consumers.
+ * <pre> {@code
+ * class Producer implements Runnable {
+ *   private final BlockingQueue queue;
+ *   Producer(BlockingQueue q) { queue = q; }
+ *   public void run() {
+ *     try {
+ *       while (true) { queue.put(produce()); }
+ *     } catch (InterruptedException ex) { ... handle ...}
+ *   }
+ *   Object produce() { ... }
+ * }
+ *
+ * class Consumer implements Runnable {
+ *   private final BlockingQueue queue;
+ *   Consumer(BlockingQueue q) { queue = q; }
+ *   public void run() {
+ *     try {
+ *       while (true) { consume(queue.take()); }
+ *     } catch (InterruptedException ex) { ... handle ...}
+ *   }
+ *   void consume(Object x) { ... }
+ * }
+ *
+ * class Setup {
+ *   void main() {
+ *     BlockingQueue q = new SomeQueueImplementation();
+ *     Producer p = new Producer(q);
+ *     Consumer c1 = new Consumer(q);
+ *     Consumer c2 = new Consumer(q);
+ *     new Thread(p).start();
+ *     new Thread(c1).start();
+ *     new Thread(c2).start();
+ *   }
+ * }}</pre>
+ *
+ * <p>Memory consistency effects: As with other concurrent
+ * collections, actions in a thread prior to placing an object into a
+ * {@code BlockingQueue}
+ * <a href="package-summary.html#MemoryVisibility"><i>happen-before</i></a>
+ * actions subsequent to the access or removal of that element from
+ * the {@code BlockingQueue} in another thread.
+ *
+ * <p>This interface is a member of the
+ * <a href="{@docRoot}/java/util/package-summary.html#CollectionsFramework">
+ * Java Collections Framework</a>.
+ *
+ * @since 1.5
+ * @author Doug Lea
+ * @param <E> the type of elements held in this queue
+ */
+public interface BlockingQueue<E> extends Queue<E> {
+    /**
+     * Inserts the specified element into this queue if it is possible to do
+     * so immediately without violating capacity restrictions, returning
+     * {@code true} upon success and throwing an
+     * {@code IllegalStateException} if no space is currently available.
+     * When using a capacity-restricted queue, it is generally preferable to
+     * use {@link #offer(Object) offer}.
+     *
+     * @param e the element to add
+     * @return {@code true} (as specified by {@link Collection#add})
+     * @throws IllegalStateException if the element cannot be added at this
+     *         time due to capacity restrictions
+     * @throws ClassCastException if the class of the specified element
+     *         prevents it from being added to this queue
+     * @throws NullPointerException if the specified element is null
+     * @throws IllegalArgumentException if some property of the specified
+     *         element prevents it from being added to this queue
+     */
+    boolean add(E e);
+
+    /**
+     * Inserts the specified element into this queue if it is possible to do
+     * so immediately without violating capacity restrictions, returning
+     * {@code true} upon success and {@code false} if no space is currently
+     * available.  When using a capacity-restricted queue, this method is
+     * generally preferable to {@link #add}, which can fail to insert an
+     * element only by throwing an exception.
+     *
+     * @param e the element to add
+     * @return {@code true} if the element was added to this queue, else
+     *         {@code false}
+     * @throws ClassCastException if the class of the specified element
+     *         prevents it from being added to this queue
+     * @throws NullPointerException if the specified element is null
+     * @throws IllegalArgumentException if some property of the specified
+     *         element prevents it from being added to this queue
+     */
+    boolean offer(E e);
+
+    /**
+     * Inserts the specified element into this queue, waiting if necessary
+     * for space to become available.
+     *
+     * @param e the element to add
+     * @throws InterruptedException if interrupted while waiting
+     * @throws ClassCastException if the class of the specified element
+     *         prevents it from being added to this queue
+     * @throws NullPointerException if the specified element is null
+     * @throws IllegalArgumentException if some property of the specified
+     *         element prevents it from being added to this queue
+     */
+    void put(E e) throws InterruptedException;
+
+    /**
+     * Inserts the specified element into this queue, waiting up to the
+     * specified wait time if necessary for space to become available.
+     *
+     * @param e the element to add
+     * @param timeout how long to wait before giving up, in units of
+     *        {@code unit}
+     * @param unit a {@code TimeUnit} determining how to interpret the
+     *        {@code timeout} parameter
+     * @return {@code true} if successful, or {@code false} if
+     *         the specified waiting time elapses before space is available
+     * @throws InterruptedException if interrupted while waiting
+     * @throws ClassCastException if the class of the specified element
+     *         prevents it from being added to this queue
+     * @throws NullPointerException if the specified element is null
+     * @throws IllegalArgumentException if some property of the specified
+     *         element prevents it from being added to this queue
+     */
+    boolean offer(E e, long timeout, TimeUnit unit)
+        throws InterruptedException;
+
+    /**
+     * Retrieves and removes the head of this queue, waiting if necessary
+     * until an element becomes available.
+     *
+     * @return the head of this queue
+     * @throws InterruptedException if interrupted while waiting
+     */
+    E take() throws InterruptedException;
+
+    /**
+     * Retrieves and removes the head of this queue, waiting up to the
+     * specified wait time if necessary for an element to become available.
+     *
+     * @param timeout how long to wait before giving up, in units of
+     *        {@code unit}
+     * @param unit a {@code TimeUnit} determining how to interpret the
+     *        {@code timeout} parameter
+     * @return the head of this queue, or {@code null} if the
+     *         specified waiting time elapses before an element is available
+     * @throws InterruptedException if interrupted while waiting
+     */
+    E poll(long timeout, TimeUnit unit)
+        throws InterruptedException;
+
+    /**
+     * Returns the number of additional elements that this queue can ideally
+     * (in the absence of memory or resource constraints) accept without
+     * blocking, or {@code Integer.MAX_VALUE} if there is no intrinsic
+     * limit.
+     *
+     * <p>Note that you <em>cannot</em> always tell if an attempt to insert
+     * an element will succeed by inspecting {@code remainingCapacity}
+     * because it may be the case that another thread is about to
+     * insert or remove an element.
+     *
+     * @return the remaining capacity
+     */
+    int remainingCapacity();
+
+    /**
+     * Removes a single instance of the specified element from this queue,
+     * if it is present.  More formally, removes an element {@code e} such
+     * that {@code o.equals(e)}, if this queue contains one or more such
+     * elements.
+     * Returns {@code true} if this queue contained the specified element
+     * (or equivalently, if this queue changed as a result of the call).
+     *
+     * @param o element to be removed from this queue, if present
+     * @return {@code true} if this queue changed as a result of the call
+     * @throws ClassCastException if the class of the specified element
+     *         is incompatible with this queue
+     * (<a href="{@docRoot}/java/util/Collection.html#optional-restrictions">optional</a>)
+     * @throws NullPointerException if the specified element is null
+     * (<a href="{@docRoot}/java/util/Collection.html#optional-restrictions">optional</a>)
+     */
+    boolean remove(Object o);
+
+    /**
+     * Returns {@code true} if this queue contains the specified element.
+     * More formally, returns {@code true} if and only if this queue contains
+     * at least one element {@code e} such that {@code o.equals(e)}.
+     *
+     * @param o object to be checked for containment in this queue
+     * @return {@code true} if this queue contains the specified element
+     * @throws ClassCastException if the class of the specified element
+     *         is incompatible with this queue
+     * (<a href="{@docRoot}/java/util/Collection.html#optional-restrictions">optional</a>)
+     * @throws NullPointerException if the specified element is null
+     * (<a href="{@docRoot}/java/util/Collection.html#optional-restrictions">optional</a>)
+     */
+    boolean contains(Object o);
+
+    /**
+     * Removes all available elements from this queue and adds them
+     * to the given collection.  This operation may be more
+     * efficient than repeatedly polling this queue.  A failure
+     * encountered while attempting to add elements to
+     * collection {@code c} may result in elements being in neither,
+     * either or both collections when the associated exception is
+     * thrown.  Attempts to drain a queue to itself result in
+     * {@code IllegalArgumentException}. Further, the behavior of
+     * this operation is undefined if the specified collection is
+     * modified while the operation is in progress.
+     *
+     * @param c the collection to transfer elements into
+     * @return the number of elements transferred
+     * @throws UnsupportedOperationException if addition of elements
+     *         is not supported by the specified collection
+     * @throws ClassCastException if the class of an element of this queue
+     *         prevents it from being added to the specified collection
+     * @throws NullPointerException if the specified collection is null
+     * @throws IllegalArgumentException if the specified collection is this
+     *         queue, or some property of an element of this queue prevents
+     *         it from being added to the specified collection
+     */
+    int drainTo(Collection<? super E> c);
+
+    /**
+     * Removes at most the given number of available elements from
+     * this queue and adds them to the given collection.  A failure
+     * encountered while attempting to add elements to
+     * collection {@code c} may result in elements being in neither,
+     * either or both collections when the associated exception is
+     * thrown.  Attempts to drain a queue to itself result in
+     * {@code IllegalArgumentException}. Further, the behavior of
+     * this operation is undefined if the specified collection is
+     * modified while the operation is in progress.
+     *
+     * @param c the collection to transfer elements into
+     * @param maxElements the maximum number of elements to transfer
+     * @return the number of elements transferred
+     * @throws UnsupportedOperationException if addition of elements
+     *         is not supported by the specified collection
+     * @throws ClassCastException if the class of an element of this queue
+     *         prevents it from being added to the specified collection
+     * @throws NullPointerException if the specified collection is null
+     * @throws IllegalArgumentException if the specified collection is this
+     *         queue, or some property of an element of this queue prevents
+     *         it from being added to the specified collection
+     */
+    int drainTo(Collection<? super E> c, int maxElements);
+}

src/java.base/share/classes/java/util/concurrent/BrokenBarrierException.java

@@ -0,0 +1,66 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent;
+
+/**
+ * Exception thrown when a thread tries to wait upon a barrier that is
+ * in a broken state, or which enters the broken state while the thread
+ * is waiting.
+ *
+ * @see CyclicBarrier
+ *
+ * @since 1.5
+ * @author Doug Lea
+ */
+public class BrokenBarrierException extends Exception {
+    private static final long serialVersionUID = 7117394618823254244L;
+
+    /**
+     * Constructs a {@code BrokenBarrierException} with no specified detail
+     * message.
+     */
+    public BrokenBarrierException() {}
+
+    /**
+     * Constructs a {@code BrokenBarrierException} with the specified
+     * detail message.
+     *
+     * @param message the detail message
+     */
+    public BrokenBarrierException(String message) {
+        super(message);
+    }
+}

src/java.base/share/classes/java/util/concurrent/Callable.java

@@ -0,0 +1,66 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent;
+
+/**
+ * A task that returns a result and may throw an exception.
+ * Implementors define a single method with no arguments called
+ * {@code call}.
+ *
+ * <p>The {@code Callable} interface is similar to {@link
+ * java.lang.Runnable}, in that both are designed for classes whose
+ * instances are potentially executed by another thread.  A
+ * {@code Runnable}, however, does not return a result and cannot
+ * throw a checked exception.
+ *
+ * <p>The {@link Executors} class contains utility methods to
+ * convert from other common forms to {@code Callable} classes.
+ *
+ * @see Executor
+ * @since 1.5
+ * @author Doug Lea
+ * @param <V> the result type of method {@code call}
+ */
+@FunctionalInterface
+public interface Callable<V> {
+    /**
+     * Computes a result, or throws an exception if unable to do so.
+     *
+     * @return computed result
+     * @throws Exception if unable to compute a result
+     */
+    V call() throws Exception;
+}

src/java.base/share/classes/java/util/concurrent/CancellationException.java

@@ -0,0 +1,63 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent;
+
+/**
+ * Exception indicating that the result of a value-producing task,
+ * such as a {@link FutureTask}, cannot be retrieved because the task
+ * was cancelled.
+ *
+ * @since 1.5
+ * @author Doug Lea
+ */
+public class CancellationException extends IllegalStateException {
+    private static final long serialVersionUID = -9202173006928992231L;
+
+    /**
+     * Constructs a {@code CancellationException} with no detail message.
+     */
+    public CancellationException() {}
+
+    /**
+     * Constructs a {@code CancellationException} with the specified detail
+     * message.
+     *
+     * @param message the detail message
+     */
+    public CancellationException(String message) {
+        super(message);
+    }
+}

src/java.base/share/classes/java/util/concurrent/CompletionException.java

@@ -0,0 +1,90 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent;
+
+/**
+ * Exception thrown when an error or other exception is encountered
+ * in the course of completing a result or task.
+ *
+ * @since 1.8
+ * @author Doug Lea
+ */
+public class CompletionException extends RuntimeException {
+    private static final long serialVersionUID = 7830266012832686185L;
+
+    /**
+     * Constructs a {@code CompletionException} with no detail message.
+     * The cause is not initialized, and may subsequently be
+     * initialized by a call to {@link #initCause(Throwable) initCause}.
+     */
+    protected CompletionException() { }
+
+    /**
+     * Constructs a {@code CompletionException} with the specified detail
+     * message. The cause is not initialized, and may subsequently be
+     * initialized by a call to {@link #initCause(Throwable) initCause}.
+     *
+     * @param message the detail message
+     */
+    protected CompletionException(String message) {
+        super(message);
+    }
+
+    /**
+     * Constructs a {@code CompletionException} with the specified detail
+     * message and cause.
+     *
+     * @param  message the detail message
+     * @param  cause the cause (which is saved for later retrieval by the
+     *         {@link #getCause()} method)
+     */
+    public CompletionException(String message, Throwable cause) {
+        super(message, cause);
+    }
+
+    /**
+     * Constructs a {@code CompletionException} with the specified cause.
+     * The detail message is set to {@code (cause == null ? null :
+     * cause.toString())} (which typically contains the class and
+     * detail message of {@code cause}).
+     *
+     * @param  cause the cause (which is saved for later retrieval by the
+     *         {@link #getCause()} method)
+     */
+    public CompletionException(Throwable cause) {
+        super(cause);
+    }
+}

src/java.base/share/classes/java/util/concurrent/CompletionService.java

@@ -0,0 +1,126 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent;
+
+/**
+ * A service that decouples the production of new asynchronous tasks
+ * from the consumption of the results of completed tasks.  Producers
+ * {@code submit} tasks for execution. Consumers {@code take}
+ * completed tasks and process their results in the order they
+ * complete.  A {@code CompletionService} can for example be used to
+ * manage asynchronous I/O, in which tasks that perform reads are
+ * submitted in one part of a program or system, and then acted upon
+ * in a different part of the program when the reads complete,
+ * possibly in a different order than they were requested.
+ *
+ * <p>Typically, a {@code CompletionService} relies on a separate
+ * {@link Executor} to actually execute the tasks, in which case the
+ * {@code CompletionService} only manages an internal completion
+ * queue. The {@link ExecutorCompletionService} class provides an
+ * implementation of this approach.
+ *
+ * <p>Memory consistency effects: Actions in a thread prior to
+ * submitting a task to a {@code CompletionService}
+ * <a href="package-summary.html#MemoryVisibility"><i>happen-before</i></a>
+ * actions taken by that task, which in turn <i>happen-before</i>
+ * actions following a successful return from the corresponding {@code take()}.
+ *
+ * @since 1.5
+ */
+public interface CompletionService<V> {
+    /**
+     * Submits a value-returning task for execution and returns a Future
+     * representing the pending results of the task.  Upon completion,
+     * this task may be taken or polled.
+     *
+     * @param task the task to submit
+     * @return a Future representing pending completion of the task
+     * @throws RejectedExecutionException if the task cannot be
+     *         scheduled for execution
+     * @throws NullPointerException if the task is null
+     */
+    Future<V> submit(Callable<V> task);
+
+    /**
+     * Submits a Runnable task for execution and returns a Future
+     * representing that task.  Upon completion, this task may be
+     * taken or polled.
+     *
+     * @param task the task to submit
+     * @param result the result to return upon successful completion
+     * @return a Future representing pending completion of the task,
+     *         and whose {@code get()} method will return the given
+     *         result value upon completion
+     * @throws RejectedExecutionException if the task cannot be
+     *         scheduled for execution
+     * @throws NullPointerException if the task is null
+     */
+    Future<V> submit(Runnable task, V result);
+
+    /**
+     * Retrieves and removes the Future representing the next
+     * completed task, waiting if none are yet present.
+     *
+     * @return the Future representing the next completed task
+     * @throws InterruptedException if interrupted while waiting
+     */
+    Future<V> take() throws InterruptedException;
+
+    /**
+     * Retrieves and removes the Future representing the next
+     * completed task, or {@code null} if none are present.
+     *
+     * @return the Future representing the next completed task, or
+     *         {@code null} if none are present
+     */
+    Future<V> poll();
+
+    /**
+     * Retrieves and removes the Future representing the next
+     * completed task, waiting if necessary up to the specified wait
+     * time if none are yet present.
+     *
+     * @param timeout how long to wait before giving up, in units of
+     *        {@code unit}
+     * @param unit a {@code TimeUnit} determining how to interpret the
+     *        {@code timeout} parameter
+     * @return the Future representing the next completed task or
+     *         {@code null} if the specified waiting time elapses
+     *         before one is present
+     * @throws InterruptedException if interrupted while waiting
+     */
+    Future<V> poll(long timeout, TimeUnit unit) throws InterruptedException;
+}

src/java.base/share/classes/java/util/concurrent/CompletionStage.java

@@ -0,0 +1,865 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent;
+
+import java.util.function.BiConsumer;
+import java.util.function.BiFunction;
+import java.util.function.Consumer;
+import java.util.function.Function;
+
+/**
+ * A stage of a possibly asynchronous computation, that performs an
+ * action or computes a value when another CompletionStage completes.
+ * A stage completes upon termination of its computation, but this may
+ * in turn trigger other dependent stages.  The functionality defined
+ * in this interface takes only a few basic forms, which expand out to
+ * a larger set of methods to capture a range of usage styles:
+ *
+ * <ul>
+ *
+ * <li>The computation performed by a stage may be expressed as a
+ * Function, Consumer, or Runnable (using methods with names including
+ * <em>apply</em>, <em>accept</em>, or <em>run</em>, respectively)
+ * depending on whether it requires arguments and/or produces results.
+ * For example:
+ * <pre> {@code
+ * stage.thenApply(x -> square(x))
+ *      .thenAccept(x -> System.out.print(x))
+ *      .thenRun(() -> System.out.println());}</pre>
+ *
+ * An additional form (<em>compose</em>) allows the construction of
+ * computation pipelines from functions returning completion stages.
+ *
+ * <p>Any argument to a stage's computation is the outcome of a
+ * triggering stage's computation.
+ *
+ * <li>One stage's execution may be triggered by completion of a
+ * single stage, or both of two stages, or either of two stages.
+ * Dependencies on a single stage are arranged using methods with
+ * prefix <em>then</em>. Those triggered by completion of
+ * <em>both</em> of two stages may <em>combine</em> their results or
+ * effects, using correspondingly named methods. Those triggered by
+ * <em>either</em> of two stages make no guarantees about which of the
+ * results or effects are used for the dependent stage's computation.
+ *
+ * <li>Dependencies among stages control the triggering of
+ * computations, but do not otherwise guarantee any particular
+ * ordering. Additionally, execution of a new stage's computations may
+ * be arranged in any of three ways: default execution, default
+ * asynchronous execution (using methods with suffix <em>async</em>
+ * that employ the stage's default asynchronous execution facility),
+ * or custom (via a supplied {@link Executor}).  The execution
+ * properties of default and async modes are specified by
+ * CompletionStage implementations, not this interface. Methods with
+ * explicit Executor arguments may have arbitrary execution
+ * properties, and might not even support concurrent execution, but
+ * are arranged for processing in a way that accommodates asynchrony.
+ *
+ * <li>Two method forms ({@link #handle handle} and {@link
+ * #whenComplete whenComplete}) support unconditional computation
+ * whether the triggering stage completed normally or exceptionally.
+ * Method {@link #exceptionally exceptionally} supports computation
+ * only when the triggering stage completes exceptionally, computing a
+ * replacement result, similarly to the java {@code catch} keyword.
+ * In all other cases, if a stage's computation terminates abruptly
+ * with an (unchecked) exception or error, then all dependent stages
+ * requiring its completion complete exceptionally as well, with a
+ * {@link CompletionException} holding the exception as its cause.  If
+ * a stage is dependent on <em>both</em> of two stages, and both
+ * complete exceptionally, then the CompletionException may correspond
+ * to either one of these exceptions.  If a stage is dependent on
+ * <em>either</em> of two others, and only one of them completes
+ * exceptionally, no guarantees are made about whether the dependent
+ * stage completes normally or exceptionally. In the case of method
+ * {@code whenComplete}, when the supplied action itself encounters an
+ * exception, then the stage completes exceptionally with this
+ * exception unless the source stage also completed exceptionally, in
+ * which case the exceptional completion from the source stage is
+ * given preference and propagated to the dependent stage.
+ *
+ * </ul>
+ *
+ * <p>All methods adhere to the above triggering, execution, and
+ * exceptional completion specifications (which are not repeated in
+ * individual method specifications). Additionally, while arguments
+ * used to pass a completion result (that is, for parameters of type
+ * {@code T}) for methods accepting them may be null, passing a null
+ * value for any other parameter will result in a {@link
+ * NullPointerException} being thrown.
+ *
+ * <p>Method form {@link #handle handle} is the most general way of
+ * creating a continuation stage, unconditionally performing a
+ * computation that is given both the result and exception (if any) of
+ * the triggering CompletionStage, and computing an arbitrary result.
+ * Method {@link #whenComplete whenComplete} is similar, but preserves
+ * the result of the triggering stage instead of computing a new one.
+ * Because a stage's normal result may be {@code null}, both methods
+ * should have a computation structured thus:
+ *
+ * <pre>{@code (result, exception) -> {
+ *   if (exception == null) {
+ *     // triggering stage completed normally
+ *   } else {
+ *     // triggering stage completed exceptionally
+ *   }
+ * }}</pre>
+ *
+ * <p>This interface does not define methods for initially creating,
+ * forcibly completing normally or exceptionally, probing completion
+ * status or results, or awaiting completion of a stage.
+ * Implementations of CompletionStage may provide means of achieving
+ * such effects, as appropriate.  Method {@link #toCompletableFuture}
+ * enables interoperability among different implementations of this
+ * interface by providing a common conversion type.
+ *
+ * @author Doug Lea
+ * @since 1.8
+ */
+public interface CompletionStage<T> {
+
+    /**
+     * Returns a new CompletionStage that, when this stage completes
+     * normally, is executed with this stage's result as the argument
+     * to the supplied function.
+     *
+     * <p>This method is analogous to
+     * {@link java.util.Optional#map Optional.map} and
+     * {@link java.util.stream.Stream#map Stream.map}.
+     *
+     * <p>See the {@link CompletionStage} documentation for rules
+     * covering exceptional completion.
+     *
+     * @param fn the function to use to compute the value of the
+     * returned CompletionStage
+     * @param <U> the function's return type
+     * @return the new CompletionStage
+     */
+    public <U> CompletionStage<U> thenApply(Function<? super T,? extends U> fn);
+
+    /**
+     * Returns a new CompletionStage that, when this stage completes
+     * normally, is executed using this stage's default asynchronous
+     * execution facility, with this stage's result as the argument to
+     * the supplied function.
+     *
+     * See the {@link CompletionStage} documentation for rules
+     * covering exceptional completion.
+     *
+     * @param fn the function to use to compute the value of the
+     * returned CompletionStage
+     * @param <U> the function's return type
+     * @return the new CompletionStage
+     */
+    public <U> CompletionStage<U> thenApplyAsync
+        (Function<? super T,? extends U> fn);
+
+    /**
+     * Returns a new CompletionStage that, when this stage completes
+     * normally, is executed using the supplied Executor, with this
+     * stage's result as the argument to the supplied function.
+     *
+     * See the {@link CompletionStage} documentation for rules
+     * covering exceptional completion.
+     *
+     * @param fn the function to use to compute the value of the
+     * returned CompletionStage
+     * @param executor the executor to use for asynchronous execution
+     * @param <U> the function's return type
+     * @return the new CompletionStage
+     */
+    public <U> CompletionStage<U> thenApplyAsync
+        (Function<? super T,? extends U> fn,
+         Executor executor);
+
+    /**
+     * Returns a new CompletionStage that, when this stage completes
+     * normally, is executed with this stage's result as the argument
+     * to the supplied action.
+     *
+     * See the {@link CompletionStage} documentation for rules
+     * covering exceptional completion.
+     *
+     * @param action the action to perform before completing the
+     * returned CompletionStage
+     * @return the new CompletionStage
+     */
+    public CompletionStage<Void> thenAccept(Consumer<? super T> action);
+
+    /**
+     * Returns a new CompletionStage that, when this stage completes
+     * normally, is executed using this stage's default asynchronous
+     * execution facility, with this stage's result as the argument to
+     * the supplied action.
+     *
+     * See the {@link CompletionStage} documentation for rules
+     * covering exceptional completion.
+     *
+     * @param action the action to perform before completing the
+     * returned CompletionStage
+     * @return the new CompletionStage
+     */
+    public CompletionStage<Void> thenAcceptAsync(Consumer<? super T> action);
+
+    /**
+     * Returns a new CompletionStage that, when this stage completes
+     * normally, is executed using the supplied Executor, with this
+     * stage's result as the argument to the supplied action.
+     *
+     * See the {@link CompletionStage} documentation for rules
+     * covering exceptional completion.
+     *
+     * @param action the action to perform before completing the
+     * returned CompletionStage
+     * @param executor the executor to use for asynchronous execution
+     * @return the new CompletionStage
+     */
+    public CompletionStage<Void> thenAcceptAsync(Consumer<? super T> action,
+                                                 Executor executor);
+    /**
+     * Returns a new CompletionStage that, when this stage completes
+     * normally, executes the given action.
+     *
+     * See the {@link CompletionStage} documentation for rules
+     * covering exceptional completion.
+     *
+     * @param action the action to perform before completing the
+     * returned CompletionStage
+     * @return the new CompletionStage
+     */
+    public CompletionStage<Void> thenRun(Runnable action);
+
+    /**
+     * Returns a new CompletionStage that, when this stage completes
+     * normally, executes the given action using this stage's default
+     * asynchronous execution facility.
+     *
+     * See the {@link CompletionStage} documentation for rules
+     * covering exceptional completion.
+     *
+     * @param action the action to perform before completing the
+     * returned CompletionStage
+     * @return the new CompletionStage
+     */
+    public CompletionStage<Void> thenRunAsync(Runnable action);
+
+    /**
+     * Returns a new CompletionStage that, when this stage completes
+     * normally, executes the given action using the supplied Executor.
+     *
+     * See the {@link CompletionStage} documentation for rules
+     * covering exceptional completion.
+     *
+     * @param action the action to perform before completing the
+     * returned CompletionStage
+     * @param executor the executor to use for asynchronous execution
+     * @return the new CompletionStage
+     */
+    public CompletionStage<Void> thenRunAsync(Runnable action,
+                                              Executor executor);
+
+    /**
+     * Returns a new CompletionStage that, when this and the other
+     * given stage both complete normally, is executed with the two
+     * results as arguments to the supplied function.
+     *
+     * See the {@link CompletionStage} documentation for rules
+     * covering exceptional completion.
+     *
+     * @param other the other CompletionStage
+     * @param fn the function to use to compute the value of the
+     * returned CompletionStage
+     * @param <U> the type of the other CompletionStage's result
+     * @param <V> the function's return type
+     * @return the new CompletionStage
+     */
+    public <U,V> CompletionStage<V> thenCombine
+        (CompletionStage<? extends U> other,
+         BiFunction<? super T,? super U,? extends V> fn);
+
+    /**
+     * Returns a new CompletionStage that, when this and the other
+     * given stage both complete normally, is executed using this
+     * stage's default asynchronous execution facility, with the two
+     * results as arguments to the supplied function.
+     *
+     * See the {@link CompletionStage} documentation for rules
+     * covering exceptional completion.
+     *
+     * @param other the other CompletionStage
+     * @param fn the function to use to compute the value of the
+     * returned CompletionStage
+     * @param <U> the type of the other CompletionStage's result
+     * @param <V> the function's return type
+     * @return the new CompletionStage
+     */
+    public <U,V> CompletionStage<V> thenCombineAsync
+        (CompletionStage<? extends U> other,
+         BiFunction<? super T,? super U,? extends V> fn);
+
+    /**
+     * Returns a new CompletionStage that, when this and the other
+     * given stage both complete normally, is executed using the
+     * supplied executor, with the two results as arguments to the
+     * supplied function.
+     *
+     * See the {@link CompletionStage} documentation for rules
+     * covering exceptional completion.
+     *
+     * @param other the other CompletionStage
+     * @param fn the function to use to compute the value of the
+     * returned CompletionStage
+     * @param executor the executor to use for asynchronous execution
+     * @param <U> the type of the other CompletionStage's result
+     * @param <V> the function's return type
+     * @return the new CompletionStage
+     */
+    public <U,V> CompletionStage<V> thenCombineAsync
+        (CompletionStage<? extends U> other,
+         BiFunction<? super T,? super U,? extends V> fn,
+         Executor executor);
+
+    /**
+     * Returns a new CompletionStage that, when this and the other
+     * given stage both complete normally, is executed with the two
+     * results as arguments to the supplied action.
+     *
+     * See the {@link CompletionStage} documentation for rules
+     * covering exceptional completion.
+     *
+     * @param other the other CompletionStage
+     * @param action the action to perform before completing the
+     * returned CompletionStage
+     * @param <U> the type of the other CompletionStage's result
+     * @return the new CompletionStage
+     */
+    public <U> CompletionStage<Void> thenAcceptBoth
+        (CompletionStage<? extends U> other,
+         BiConsumer<? super T, ? super U> action);
+
+    /**
+     * Returns a new CompletionStage that, when this and the other
+     * given stage both complete normally, is executed using this
+     * stage's default asynchronous execution facility, with the two
+     * results as arguments to the supplied action.
+     *
+     * See the {@link CompletionStage} documentation for rules
+     * covering exceptional completion.
+     *
+     * @param other the other CompletionStage
+     * @param action the action to perform before completing the
+     * returned CompletionStage
+     * @param <U> the type of the other CompletionStage's result
+     * @return the new CompletionStage
+     */
+    public <U> CompletionStage<Void> thenAcceptBothAsync
+        (CompletionStage<? extends U> other,
+         BiConsumer<? super T, ? super U> action);
+
+    /**
+     * Returns a new CompletionStage that, when this and the other
+     * given stage both complete normally, is executed using the
+     * supplied executor, with the two results as arguments to the
+     * supplied action.
+     *
+     * See the {@link CompletionStage} documentation for rules
+     * covering exceptional completion.
+     *
+     * @param other the other CompletionStage
+     * @param action the action to perform before completing the
+     * returned CompletionStage
+     * @param executor the executor to use for asynchronous execution
+     * @param <U> the type of the other CompletionStage's result
+     * @return the new CompletionStage
+     */
+    public <U> CompletionStage<Void> thenAcceptBothAsync
+        (CompletionStage<? extends U> other,
+         BiConsumer<? super T, ? super U> action,
+         Executor executor);
+
+    /**
+     * Returns a new CompletionStage that, when this and the other
+     * given stage both complete normally, executes the given action.
+     *
+     * See the {@link CompletionStage} documentation for rules
+     * covering exceptional completion.
+     *
+     * @param other the other CompletionStage
+     * @param action the action to perform before completing the
+     * returned CompletionStage
+     * @return the new CompletionStage
+     */
+    public CompletionStage<Void> runAfterBoth(CompletionStage<?> other,
+                                              Runnable action);
+    /**
+     * Returns a new CompletionStage that, when this and the other
+     * given stage both complete normally, executes the given action
+     * using this stage's default asynchronous execution facility.
+     *
+     * See the {@link CompletionStage} documentation for rules
+     * covering exceptional completion.
+     *
+     * @param other the other CompletionStage
+     * @param action the action to perform before completing the
+     * returned CompletionStage
+     * @return the new CompletionStage
+     */
+    public CompletionStage<Void> runAfterBothAsync(CompletionStage<?> other,
+                                                   Runnable action);
+
+    /**
+     * Returns a new CompletionStage that, when this and the other
+     * given stage both complete normally, executes the given action
+     * using the supplied executor.
+     *
+     * See the {@link CompletionStage} documentation for rules
+     * covering exceptional completion.
+     *
+     * @param other the other CompletionStage
+     * @param action the action to perform before completing the
+     * returned CompletionStage
+     * @param executor the executor to use for asynchronous execution
+     * @return the new CompletionStage
+     */
+    public CompletionStage<Void> runAfterBothAsync(CompletionStage<?> other,
+                                                   Runnable action,
+                                                   Executor executor);
+    /**
+     * Returns a new CompletionStage that, when either this or the
+     * other given stage complete normally, is executed with the
+     * corresponding result as argument to the supplied function.
+     *
+     * See the {@link CompletionStage} documentation for rules
+     * covering exceptional completion.
+     *
+     * @param other the other CompletionStage
+     * @param fn the function to use to compute the value of the
+     * returned CompletionStage
+     * @param <U> the function's return type
+     * @return the new CompletionStage
+     */
+    public <U> CompletionStage<U> applyToEither
+        (CompletionStage<? extends T> other,
+         Function<? super T, U> fn);
+
+    /**
+     * Returns a new CompletionStage that, when either this or the
+     * other given stage complete normally, is executed using this
+     * stage's default asynchronous execution facility, with the
+     * corresponding result as argument to the supplied function.
+     *
+     * See the {@link CompletionStage} documentation for rules
+     * covering exceptional completion.
+     *
+     * @param other the other CompletionStage
+     * @param fn the function to use to compute the value of the
+     * returned CompletionStage
+     * @param <U> the function's return type
+     * @return the new CompletionStage
+     */
+    public <U> CompletionStage<U> applyToEitherAsync
+        (CompletionStage<? extends T> other,
+         Function<? super T, U> fn);
+
+    /**
+     * Returns a new CompletionStage that, when either this or the
+     * other given stage complete normally, is executed using the
+     * supplied executor, with the corresponding result as argument to
+     * the supplied function.
+     *
+     * See the {@link CompletionStage} documentation for rules
+     * covering exceptional completion.
+     *
+     * @param other the other CompletionStage
+     * @param fn the function to use to compute the value of the
+     * returned CompletionStage
+     * @param executor the executor to use for asynchronous execution
+     * @param <U> the function's return type
+     * @return the new CompletionStage
+     */
+    public <U> CompletionStage<U> applyToEitherAsync
+        (CompletionStage<? extends T> other,
+         Function<? super T, U> fn,
+         Executor executor);
+
+    /**
+     * Returns a new CompletionStage that, when either this or the
+     * other given stage complete normally, is executed with the
+     * corresponding result as argument to the supplied action.
+     *
+     * See the {@link CompletionStage} documentation for rules
+     * covering exceptional completion.
+     *
+     * @param other the other CompletionStage
+     * @param action the action to perform before completing the
+     * returned CompletionStage
+     * @return the new CompletionStage
+     */
+    public CompletionStage<Void> acceptEither
+        (CompletionStage<? extends T> other,
+         Consumer<? super T> action);
+
+    /**
+     * Returns a new CompletionStage that, when either this or the
+     * other given stage complete normally, is executed using this
+     * stage's default asynchronous execution facility, with the
+     * corresponding result as argument to the supplied action.
+     *
+     * See the {@link CompletionStage} documentation for rules
+     * covering exceptional completion.
+     *
+     * @param other the other CompletionStage
+     * @param action the action to perform before completing the
+     * returned CompletionStage
+     * @return the new CompletionStage
+     */
+    public CompletionStage<Void> acceptEitherAsync
+        (CompletionStage<? extends T> other,
+         Consumer<? super T> action);
+
+    /**
+     * Returns a new CompletionStage that, when either this or the
+     * other given stage complete normally, is executed using the
+     * supplied executor, with the corresponding result as argument to
+     * the supplied action.
+     *
+     * See the {@link CompletionStage} documentation for rules
+     * covering exceptional completion.
+     *
+     * @param other the other CompletionStage
+     * @param action the action to perform before completing the
+     * returned CompletionStage
+     * @param executor the executor to use for asynchronous execution
+     * @return the new CompletionStage
+     */
+    public CompletionStage<Void> acceptEitherAsync
+        (CompletionStage<? extends T> other,
+         Consumer<? super T> action,
+         Executor executor);
+
+    /**
+     * Returns a new CompletionStage that, when either this or the
+     * other given stage complete normally, executes the given action.
+     *
+     * See the {@link CompletionStage} documentation for rules
+     * covering exceptional completion.
+     *
+     * @param other the other CompletionStage
+     * @param action the action to perform before completing the
+     * returned CompletionStage
+     * @return the new CompletionStage
+     */
+    public CompletionStage<Void> runAfterEither(CompletionStage<?> other,
+                                                Runnable action);
+
+    /**
+     * Returns a new CompletionStage that, when either this or the
+     * other given stage complete normally, executes the given action
+     * using this stage's default asynchronous execution facility.
+     *
+     * See the {@link CompletionStage} documentation for rules
+     * covering exceptional completion.
+     *
+     * @param other the other CompletionStage
+     * @param action the action to perform before completing the
+     * returned CompletionStage
+     * @return the new CompletionStage
+     */
+    public CompletionStage<Void> runAfterEitherAsync
+        (CompletionStage<?> other,
+         Runnable action);
+
+    /**
+     * Returns a new CompletionStage that, when either this or the
+     * other given stage complete normally, executes the given action
+     * using the supplied executor.
+     *
+     * See the {@link CompletionStage} documentation for rules
+     * covering exceptional completion.
+     *
+     * @param other the other CompletionStage
+     * @param action the action to perform before completing the
+     * returned CompletionStage
+     * @param executor the executor to use for asynchronous execution
+     * @return the new CompletionStage
+     */
+    public CompletionStage<Void> runAfterEitherAsync
+        (CompletionStage<?> other,
+         Runnable action,
+         Executor executor);
+
+    /**
+     * Returns a new CompletionStage that is completed with the same
+     * value as the CompletionStage returned by the given function.
+     *
+     * <p>When this stage completes normally, the given function is
+     * invoked with this stage's result as the argument, returning
+     * another CompletionStage.  When that stage completes normally,
+     * the CompletionStage returned by this method is completed with
+     * the same value.
+     *
+     * <p>To ensure progress, the supplied function must arrange
+     * eventual completion of its result.
+     *
+     * <p>This method is analogous to
+     * {@link java.util.Optional#flatMap Optional.flatMap} and
+     * {@link java.util.stream.Stream#flatMap Stream.flatMap}.
+     *
+     * <p>See the {@link CompletionStage} documentation for rules
+     * covering exceptional completion.
+     *
+     * @param fn the function to use to compute another CompletionStage
+     * @param <U> the type of the returned CompletionStage's result
+     * @return the new CompletionStage
+     */
+    public <U> CompletionStage<U> thenCompose
+        (Function<? super T, ? extends CompletionStage<U>> fn);
+
+    /**
+     * Returns a new CompletionStage that is completed with the same
+     * value as the CompletionStage returned by the given function,
+     * executed using this stage's default asynchronous execution
+     * facility.
+     *
+     * <p>When this stage completes normally, the given function is
+     * invoked with this stage's result as the argument, returning
+     * another CompletionStage.  When that stage completes normally,
+     * the CompletionStage returned by this method is completed with
+     * the same value.
+     *
+     * <p>To ensure progress, the supplied function must arrange
+     * eventual completion of its result.
+     *
+     * <p>See the {@link CompletionStage} documentation for rules
+     * covering exceptional completion.
+     *
+     * @param fn the function to use to compute another CompletionStage
+     * @param <U> the type of the returned CompletionStage's result
+     * @return the new CompletionStage
+     */
+    public <U> CompletionStage<U> thenComposeAsync
+        (Function<? super T, ? extends CompletionStage<U>> fn);
+
+    /**
+     * Returns a new CompletionStage that is completed with the same
+     * value as the CompletionStage returned by the given function,
+     * executed using the supplied Executor.
+     *
+     * <p>When this stage completes normally, the given function is
+     * invoked with this stage's result as the argument, returning
+     * another CompletionStage.  When that stage completes normally,
+     * the CompletionStage returned by this method is completed with
+     * the same value.
+     *
+     * <p>To ensure progress, the supplied function must arrange
+     * eventual completion of its result.
+     *
+     * <p>See the {@link CompletionStage} documentation for rules
+     * covering exceptional completion.
+     *
+     * @param fn the function to use to compute another CompletionStage
+     * @param executor the executor to use for asynchronous execution
+     * @param <U> the type of the returned CompletionStage's result
+     * @return the new CompletionStage
+     */
+    public <U> CompletionStage<U> thenComposeAsync
+        (Function<? super T, ? extends CompletionStage<U>> fn,
+         Executor executor);
+
+    /**
+     * Returns a new CompletionStage that, when this stage completes
+     * either normally or exceptionally, is executed with this stage's
+     * result and exception as arguments to the supplied function.
+     *
+     * <p>When this stage is complete, the given function is invoked
+     * with the result (or {@code null} if none) and the exception (or
+     * {@code null} if none) of this stage as arguments, and the
+     * function's result is used to complete the returned stage.
+     *
+     * @param fn the function to use to compute the value of the
+     * returned CompletionStage
+     * @param <U> the function's return type
+     * @return the new CompletionStage
+     */
+    public <U> CompletionStage<U> handle
+        (BiFunction<? super T, Throwable, ? extends U> fn);
+
+    /**
+     * Returns a new CompletionStage that, when this stage completes
+     * either normally or exceptionally, is executed using this stage's
+     * default asynchronous execution facility, with this stage's
+     * result and exception as arguments to the supplied function.
+     *
+     * <p>When this stage is complete, the given function is invoked
+     * with the result (or {@code null} if none) and the exception (or
+     * {@code null} if none) of this stage as arguments, and the
+     * function's result is used to complete the returned stage.
+     *
+     * @param fn the function to use to compute the value of the
+     * returned CompletionStage
+     * @param <U> the function's return type
+     * @return the new CompletionStage
+     */
+    public <U> CompletionStage<U> handleAsync
+        (BiFunction<? super T, Throwable, ? extends U> fn);
+
+    /**
+     * Returns a new CompletionStage that, when this stage completes
+     * either normally or exceptionally, is executed using the
+     * supplied executor, with this stage's result and exception as
+     * arguments to the supplied function.
+     *
+     * <p>When this stage is complete, the given function is invoked
+     * with the result (or {@code null} if none) and the exception (or
+     * {@code null} if none) of this stage as arguments, and the
+     * function's result is used to complete the returned stage.
+     *
+     * @param fn the function to use to compute the value of the
+     * returned CompletionStage
+     * @param executor the executor to use for asynchronous execution
+     * @param <U> the function's return type
+     * @return the new CompletionStage
+     */
+    public <U> CompletionStage<U> handleAsync
+        (BiFunction<? super T, Throwable, ? extends U> fn,
+         Executor executor);
+
+    /**
+     * Returns a new CompletionStage with the same result or exception as
+     * this stage, that executes the given action when this stage completes.
+     *
+     * <p>When this stage is complete, the given action is invoked
+     * with the result (or {@code null} if none) and the exception (or
+     * {@code null} if none) of this stage as arguments.  The returned
+     * stage is completed when the action returns.
+     *
+     * <p>Unlike method {@link #handle handle},
+     * this method is not designed to translate completion outcomes,
+     * so the supplied action should not throw an exception. However,
+     * if it does, the following rules apply: if this stage completed
+     * normally but the supplied action throws an exception, then the
+     * returned stage completes exceptionally with the supplied
+     * action's exception. Or, if this stage completed exceptionally
+     * and the supplied action throws an exception, then the returned
+     * stage completes exceptionally with this stage's exception.
+     *
+     * @param action the action to perform
+     * @return the new CompletionStage
+     */
+    public CompletionStage<T> whenComplete
+        (BiConsumer<? super T, ? super Throwable> action);
+
+    /**
+     * Returns a new CompletionStage with the same result or exception as
+     * this stage, that executes the given action using this stage's
+     * default asynchronous execution facility when this stage completes.
+     *
+     * <p>When this stage is complete, the given action is invoked with the
+     * result (or {@code null} if none) and the exception (or {@code null}
+     * if none) of this stage as arguments.  The returned stage is completed
+     * when the action returns.
+     *
+     * <p>Unlike method {@link #handleAsync(BiFunction) handleAsync},
+     * this method is not designed to translate completion outcomes,
+     * so the supplied action should not throw an exception. However,
+     * if it does, the following rules apply: If this stage completed
+     * normally but the supplied action throws an exception, then the
+     * returned stage completes exceptionally with the supplied
+     * action's exception. Or, if this stage completed exceptionally
+     * and the supplied action throws an exception, then the returned
+     * stage completes exceptionally with this stage's exception.
+     *
+     * @param action the action to perform
+     * @return the new CompletionStage
+     */
+    public CompletionStage<T> whenCompleteAsync
+        (BiConsumer<? super T, ? super Throwable> action);
+
+    /**
+     * Returns a new CompletionStage with the same result or exception as
+     * this stage, that executes the given action using the supplied
+     * Executor when this stage completes.
+     *
+     * <p>When this stage is complete, the given action is invoked with the
+     * result (or {@code null} if none) and the exception (or {@code null}
+     * if none) of this stage as arguments.  The returned stage is completed
+     * when the action returns.
+     *
+     * <p>Unlike method {@link #handleAsync(BiFunction,Executor) handleAsync},
+     * this method is not designed to translate completion outcomes,
+     * so the supplied action should not throw an exception. However,
+     * if it does, the following rules apply: If this stage completed
+     * normally but the supplied action throws an exception, then the
+     * returned stage completes exceptionally with the supplied
+     * action's exception. Or, if this stage completed exceptionally
+     * and the supplied action throws an exception, then the returned
+     * stage completes exceptionally with this stage's exception.
+     *
+     * @param action the action to perform
+     * @param executor the executor to use for asynchronous execution
+     * @return the new CompletionStage
+     */
+    public CompletionStage<T> whenCompleteAsync
+        (BiConsumer<? super T, ? super Throwable> action,
+         Executor executor);
+
+    /**
+     * Returns a new CompletionStage that, when this stage completes
+     * exceptionally, is executed with this stage's exception as the
+     * argument to the supplied function.  Otherwise, if this stage
+     * completes normally, then the returned stage also completes
+     * normally with the same value.
+     *
+     * @param fn the function to use to compute the value of the
+     * returned CompletionStage if this CompletionStage completed
+     * exceptionally
+     * @return the new CompletionStage
+     */
+    public CompletionStage<T> exceptionally
+        (Function<Throwable, ? extends T> fn);
+
+    /**
+     * Returns a {@link CompletableFuture} maintaining the same
+     * completion properties as this stage. If this stage is already a
+     * CompletableFuture, this method may return this stage itself.
+     * Otherwise, invocation of this method may be equivalent in
+     * effect to {@code thenApply(x -> x)}, but returning an instance
+     * of type {@code CompletableFuture}.
+     *
+     * @return the CompletableFuture
+     */
+    public CompletableFuture<T> toCompletableFuture();
+
+}

src/java.base/share/classes/java/util/concurrent/ConcurrentMap.java

@@ -0,0 +1,500 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent;
+
+import java.util.Map;
+import java.util.Objects;
+import java.util.function.BiConsumer;
+import java.util.function.BiFunction;
+import java.util.function.Function;
+
+/**
+ * A {@link Map} providing thread safety and atomicity guarantees.
+ *
+ * <p>To maintain the specified guarantees, default implementations of
+ * methods including {@link #putIfAbsent} inherited from {@link Map}
+ * must be overridden by implementations of this interface. Similarly,
+ * implementations of the collections returned by methods {@link
+ * #keySet}, {@link #values}, and {@link #entrySet} must override
+ * methods such as {@code removeIf} when necessary to
+ * preserve atomicity guarantees.
+ *
+ * <p>Memory consistency effects: As with other concurrent
+ * collections, actions in a thread prior to placing an object into a
+ * {@code ConcurrentMap} as a key or value
+ * <a href="package-summary.html#MemoryVisibility"><i>happen-before</i></a>
+ * actions subsequent to the access or removal of that object from
+ * the {@code ConcurrentMap} in another thread.
+ *
+ * <p>This interface is a member of the
+ * <a href="{@docRoot}/java/util/package-summary.html#CollectionsFramework">
+ * Java Collections Framework</a>.
+ *
+ * @since 1.5
+ * @author Doug Lea
+ * @param <K> the type of keys maintained by this map
+ * @param <V> the type of mapped values
+ */
+public interface ConcurrentMap<K,V> extends Map<K,V> {
+
+    /**
+     * {@inheritDoc}
+     *
+     * @implNote This implementation assumes that the ConcurrentMap cannot
+     * contain null values and {@code get()} returning null unambiguously means
+     * the key is absent. Implementations which support null values
+     * <strong>must</strong> override this default implementation.
+     *
+     * @throws ClassCastException {@inheritDoc}
+     * @throws NullPointerException {@inheritDoc}
+     * @since 1.8
+     */
+    @Override
+    default V getOrDefault(Object key, V defaultValue) {
+        V v;
+        return ((v = get(key)) != null) ? v : defaultValue;
+    }
+
+    /**
+     * {@inheritDoc}
+     *
+     * @implSpec The default implementation is equivalent to, for this
+     * {@code map}:
+     * <pre> {@code
+     * for (Map.Entry<K,V> entry : map.entrySet()) {
+     *   action.accept(entry.getKey(), entry.getValue());
+     * }}</pre>
+     *
+     * @implNote The default implementation assumes that
+     * {@code IllegalStateException} thrown by {@code getKey()} or
+     * {@code getValue()} indicates that the entry has been removed and cannot
+     * be processed. Operation continues for subsequent entries.
+     *
+     * @throws NullPointerException {@inheritDoc}
+     * @since 1.8
+     */
+    @Override
+    default void forEach(BiConsumer<? super K, ? super V> action) {
+        Objects.requireNonNull(action);
+        for (Map.Entry<K,V> entry : entrySet()) {
+            K k;
+            V v;
+            try {
+                k = entry.getKey();
+                v = entry.getValue();
+            } catch (IllegalStateException ise) {
+                // this usually means the entry is no longer in the map.
+                continue;
+            }
+            action.accept(k, v);
+        }
+    }
+
+    /**
+     * If the specified key is not already associated
+     * with a value, associates it with the given value.
+     * This is equivalent to, for this {@code map}:
+     * <pre> {@code
+     * if (!map.containsKey(key))
+     *   return map.put(key, value);
+     * else
+     *   return map.get(key);}</pre>
+     *
+     * except that the action is performed atomically.
+     *
+     * @implNote This implementation intentionally re-abstracts the
+     * inappropriate default provided in {@code Map}.
+     *
+     * @param key key with which the specified value is to be associated
+     * @param value value to be associated with the specified key
+     * @return the previous value associated with the specified key, or
+     *         {@code null} if there was no mapping for the key.
+     *         (A {@code null} return can also indicate that the map
+     *         previously associated {@code null} with the key,
+     *         if the implementation supports null values.)
+     * @throws UnsupportedOperationException if the {@code put} operation
+     *         is not supported by this map
+     * @throws ClassCastException if the class of the specified key or value
+     *         prevents it from being stored in this map
+     * @throws NullPointerException if the specified key or value is null,
+     *         and this map does not permit null keys or values
+     * @throws IllegalArgumentException if some property of the specified key
+     *         or value prevents it from being stored in this map
+     */
+    V putIfAbsent(K key, V value);
+
+    /**
+     * Removes the entry for a key only if currently mapped to a given value.
+     * This is equivalent to, for this {@code map}:
+     * <pre> {@code
+     * if (map.containsKey(key)
+     *     && Objects.equals(map.get(key), value)) {
+     *   map.remove(key);
+     *   return true;
+     * } else {
+     *   return false;
+     * }}</pre>
+     *
+     * except that the action is performed atomically.
+     *
+     * @implNote This implementation intentionally re-abstracts the
+     * inappropriate default provided in {@code Map}.
+     *
+     * @param key key with which the specified value is associated
+     * @param value value expected to be associated with the specified key
+     * @return {@code true} if the value was removed
+     * @throws UnsupportedOperationException if the {@code remove} operation
+     *         is not supported by this map
+     * @throws ClassCastException if the key or value is of an inappropriate
+     *         type for this map
+     * (<a href="{@docRoot}/java/util/Collection.html#optional-restrictions">optional</a>)
+     * @throws NullPointerException if the specified key or value is null,
+     *         and this map does not permit null keys or values
+     * (<a href="{@docRoot}/java/util/Collection.html#optional-restrictions">optional</a>)
+     */
+    boolean remove(Object key, Object value);
+
+    /**
+     * Replaces the entry for a key only if currently mapped to a given value.
+     * This is equivalent to, for this {@code map}:
+     * <pre> {@code
+     * if (map.containsKey(key)
+     *     && Objects.equals(map.get(key), oldValue)) {
+     *   map.put(key, newValue);
+     *   return true;
+     * } else {
+     *   return false;
+     * }}</pre>
+     *
+     * except that the action is performed atomically.
+     *
+     * @implNote This implementation intentionally re-abstracts the
+     * inappropriate default provided in {@code Map}.
+     *
+     * @param key key with which the specified value is associated
+     * @param oldValue value expected to be associated with the specified key
+     * @param newValue value to be associated with the specified key
+     * @return {@code true} if the value was replaced
+     * @throws UnsupportedOperationException if the {@code put} operation
+     *         is not supported by this map
+     * @throws ClassCastException if the class of a specified key or value
+     *         prevents it from being stored in this map
+     * @throws NullPointerException if a specified key or value is null,
+     *         and this map does not permit null keys or values
+     * @throws IllegalArgumentException if some property of a specified key
+     *         or value prevents it from being stored in this map
+     */
+    boolean replace(K key, V oldValue, V newValue);
+
+    /**
+     * Replaces the entry for a key only if currently mapped to some value.
+     * This is equivalent to, for this {@code map}:
+     * <pre> {@code
+     * if (map.containsKey(key))
+     *   return map.put(key, value);
+     * else
+     *   return null;}</pre>
+     *
+     * except that the action is performed atomically.
+     *
+     * @implNote This implementation intentionally re-abstracts the
+     * inappropriate default provided in {@code Map}.
+     *
+     * @param key key with which the specified value is associated
+     * @param value value to be associated with the specified key
+     * @return the previous value associated with the specified key, or
+     *         {@code null} if there was no mapping for the key.
+     *         (A {@code null} return can also indicate that the map
+     *         previously associated {@code null} with the key,
+     *         if the implementation supports null values.)
+     * @throws UnsupportedOperationException if the {@code put} operation
+     *         is not supported by this map
+     * @throws ClassCastException if the class of the specified key or value
+     *         prevents it from being stored in this map
+     * @throws NullPointerException if the specified key or value is null,
+     *         and this map does not permit null keys or values
+     * @throws IllegalArgumentException if some property of the specified key
+     *         or value prevents it from being stored in this map
+     */
+    V replace(K key, V value);
+
+    /**
+     * {@inheritDoc}
+     *
+     * @implSpec
+     * <p>The default implementation is equivalent to, for this {@code map}:
+     * <pre> {@code
+     * for (Map.Entry<K,V> entry : map.entrySet()) {
+     *   K k;
+     *   V v;
+     *   do {
+     *     k = entry.getKey();
+     *     v = entry.getValue();
+     *   } while (!map.replace(k, v, function.apply(k, v)));
+     * }}</pre>
+     *
+     * The default implementation may retry these steps when multiple
+     * threads attempt updates including potentially calling the function
+     * repeatedly for a given key.
+     *
+     * <p>This implementation assumes that the ConcurrentMap cannot contain null
+     * values and {@code get()} returning null unambiguously means the key is
+     * absent. Implementations which support null values <strong>must</strong>
+     * override this default implementation.
+     *
+     * @throws UnsupportedOperationException {@inheritDoc}
+     * @throws NullPointerException {@inheritDoc}
+     * @throws ClassCastException {@inheritDoc}
+     * @throws IllegalArgumentException {@inheritDoc}
+     * @since 1.8
+     */
+    @Override
+    default void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) {
+        Objects.requireNonNull(function);
+        forEach((k,v) -> {
+            while (!replace(k, v, function.apply(k, v))) {
+                // v changed or k is gone
+                if ( (v = get(k)) == null) {
+                    // k is no longer in the map.
+                    break;
+                }
+            }
+        });
+    }
+
+    /**
+     * {@inheritDoc}
+     *
+     * @implSpec
+     * The default implementation is equivalent to the following steps for this
+     * {@code map}:
+     *
+     * <pre> {@code
+     * V oldValue, newValue;
+     * return ((oldValue = map.get(key)) == null
+     *         && (newValue = mappingFunction.apply(key)) != null
+     *         && (oldValue = map.putIfAbsent(key, newValue)) == null)
+     *   ? newValue
+     *   : oldValue;}</pre>
+     *
+     * <p>This implementation assumes that the ConcurrentMap cannot contain null
+     * values and {@code get()} returning null unambiguously means the key is
+     * absent. Implementations which support null values <strong>must</strong>
+     * override this default implementation.
+     *
+     * @throws UnsupportedOperationException {@inheritDoc}
+     * @throws ClassCastException {@inheritDoc}
+     * @throws NullPointerException {@inheritDoc}
+     * @throws IllegalArgumentException {@inheritDoc}
+     * @since 1.8
+     */
+    @Override
+    default V computeIfAbsent(K key,
+            Function<? super K, ? extends V> mappingFunction) {
+        Objects.requireNonNull(mappingFunction);
+        V oldValue, newValue;
+        return ((oldValue = get(key)) == null
+                && (newValue = mappingFunction.apply(key)) != null
+                && (oldValue = putIfAbsent(key, newValue)) == null)
+            ? newValue
+            : oldValue;
+    }
+
+    /**
+     * {@inheritDoc}
+     *
+     * @implSpec
+     * The default implementation is equivalent to performing the following
+     * steps for this {@code map}:
+     *
+     * <pre> {@code
+     * for (V oldValue; (oldValue = map.get(key)) != null; ) {
+     *   V newValue = remappingFunction.apply(key, oldValue);
+     *   if ((newValue == null)
+     *       ? map.remove(key, oldValue)
+     *       : map.replace(key, oldValue, newValue))
+     *     return newValue;
+     * }
+     * return null;}</pre>
+     * When multiple threads attempt updates, map operations and the
+     * remapping function may be called multiple times.
+     *
+     * <p>This implementation assumes that the ConcurrentMap cannot contain null
+     * values and {@code get()} returning null unambiguously means the key is
+     * absent. Implementations which support null values <strong>must</strong>
+     * override this default implementation.
+     *
+     * @throws UnsupportedOperationException {@inheritDoc}
+     * @throws ClassCastException {@inheritDoc}
+     * @throws NullPointerException {@inheritDoc}
+     * @throws IllegalArgumentException {@inheritDoc}
+     * @since 1.8
+     */
+    @Override
+    default V computeIfPresent(K key,
+            BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
+        Objects.requireNonNull(remappingFunction);
+        for (V oldValue; (oldValue = get(key)) != null; ) {
+            V newValue = remappingFunction.apply(key, oldValue);
+            if ((newValue == null)
+                ? remove(key, oldValue)
+                : replace(key, oldValue, newValue))
+                return newValue;
+        }
+        return null;
+    }
+
+    /**
+     * {@inheritDoc}
+     *
+     * @implSpec
+     * The default implementation is equivalent to performing the following
+     * steps for this {@code map}:
+     *
+     * <pre> {@code
+     * for (;;) {
+     *   V oldValue = map.get(key);
+     *   V newValue = remappingFunction.apply(key, oldValue);
+     *   if (newValue != null) {
+     *     if ((oldValue != null)
+     *       ? map.replace(key, oldValue, newValue)
+     *       : map.putIfAbsent(key, newValue) == null)
+     *       return newValue;
+     *   } else if (oldValue == null || map.remove(key, oldValue)) {
+     *     return null;
+     *   }
+     * }}</pre>
+     * When multiple threads attempt updates, map operations and the
+     * remapping function may be called multiple times.
+     *
+     * <p>This implementation assumes that the ConcurrentMap cannot contain null
+     * values and {@code get()} returning null unambiguously means the key is
+     * absent. Implementations which support null values <strong>must</strong>
+     * override this default implementation.
+     *
+     * @throws UnsupportedOperationException {@inheritDoc}
+     * @throws ClassCastException {@inheritDoc}
+     * @throws NullPointerException {@inheritDoc}
+     * @throws IllegalArgumentException {@inheritDoc}
+     * @since 1.8
+     */
+    @Override
+    default V compute(K key,
+                      BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
+        retry: for (;;) {
+            V oldValue = get(key);
+            // if putIfAbsent fails, opportunistically use its return value
+            haveOldValue: for (;;) {
+                V newValue = remappingFunction.apply(key, oldValue);
+                if (newValue != null) {
+                    if (oldValue != null) {
+                        if (replace(key, oldValue, newValue))
+                            return newValue;
+                    }
+                    else if ((oldValue = putIfAbsent(key, newValue)) == null)
+                        return newValue;
+                    else continue haveOldValue;
+                } else if (oldValue == null || remove(key, oldValue)) {
+                    return null;
+                }
+                continue retry;
+            }
+        }
+    }
+
+    /**
+     * {@inheritDoc}
+     *
+     * @implSpec
+     * The default implementation is equivalent to performing the following
+     * steps for this {@code map}:
+     *
+     * <pre> {@code
+     * for (;;) {
+     *   V oldValue = map.get(key);
+     *   if (oldValue != null) {
+     *     V newValue = remappingFunction.apply(oldValue, value);
+     *     if (newValue != null) {
+     *       if (map.replace(key, oldValue, newValue))
+     *         return newValue;
+     *     } else if (map.remove(key, oldValue)) {
+     *       return null;
+     *     }
+     *   } else if (map.putIfAbsent(key, value) == null) {
+     *     return value;
+     *   }
+     * }}</pre>
+     * When multiple threads attempt updates, map operations and the
+     * remapping function may be called multiple times.
+     *
+     * <p>This implementation assumes that the ConcurrentMap cannot contain null
+     * values and {@code get()} returning null unambiguously means the key is
+     * absent. Implementations which support null values <strong>must</strong>
+     * override this default implementation.
+     *
+     * @throws UnsupportedOperationException {@inheritDoc}
+     * @throws ClassCastException {@inheritDoc}
+     * @throws NullPointerException {@inheritDoc}
+     * @throws IllegalArgumentException {@inheritDoc}
+     * @since 1.8
+     */
+    @Override
+    default V merge(K key, V value,
+            BiFunction<? super V, ? super V, ? extends V> remappingFunction) {
+        Objects.requireNonNull(remappingFunction);
+        Objects.requireNonNull(value);
+        retry: for (;;) {
+            V oldValue = get(key);
+            // if putIfAbsent fails, opportunistically use its return value
+            haveOldValue: for (;;) {
+                if (oldValue != null) {
+                    V newValue = remappingFunction.apply(oldValue, value);
+                    if (newValue != null) {
+                        if (replace(key, oldValue, newValue))
+                            return newValue;
+                    } else if (remove(key, oldValue)) {
+                        return null;
+                    }
+                    continue retry;
+                } else {
+                    if ((oldValue = putIfAbsent(key, value)) == null)
+                        return value;
+                    continue haveOldValue;
+                }
+            }
+        }
+    }
+}

src/java.base/share/classes/java/util/concurrent/ConcurrentNavigableMap.java

@@ -0,0 +1,169 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent;
+
+import java.util.NavigableMap;
+import java.util.NavigableSet;
+
+/**
+ * A {@link ConcurrentMap} supporting {@link NavigableMap} operations,
+ * and recursively so for its navigable sub-maps.
+ *
+ * <p>This interface is a member of the
+ * <a href="{@docRoot}/java/util/package-summary.html#CollectionsFramework">
+ * Java Collections Framework</a>.
+ *
+ * @author Doug Lea
+ * @param <K> the type of keys maintained by this map
+ * @param <V> the type of mapped values
+ * @since 1.6
+ */
+public interface ConcurrentNavigableMap<K,V>
+    extends ConcurrentMap<K,V>, NavigableMap<K,V>
+{
+    /**
+     * @throws ClassCastException       {@inheritDoc}
+     * @throws NullPointerException     {@inheritDoc}
+     * @throws IllegalArgumentException {@inheritDoc}
+     */
+    ConcurrentNavigableMap<K,V> subMap(K fromKey, boolean fromInclusive,
+                                       K toKey,   boolean toInclusive);
+
+    /**
+     * @throws ClassCastException       {@inheritDoc}
+     * @throws NullPointerException     {@inheritDoc}
+     * @throws IllegalArgumentException {@inheritDoc}
+     */
+    ConcurrentNavigableMap<K,V> headMap(K toKey, boolean inclusive);
+
+    /**
+     * @throws ClassCastException       {@inheritDoc}
+     * @throws NullPointerException     {@inheritDoc}
+     * @throws IllegalArgumentException {@inheritDoc}
+     */
+    ConcurrentNavigableMap<K,V> tailMap(K fromKey, boolean inclusive);
+
+    /**
+     * @throws ClassCastException       {@inheritDoc}
+     * @throws NullPointerException     {@inheritDoc}
+     * @throws IllegalArgumentException {@inheritDoc}
+     */
+    ConcurrentNavigableMap<K,V> subMap(K fromKey, K toKey);
+
+    /**
+     * @throws ClassCastException       {@inheritDoc}
+     * @throws NullPointerException     {@inheritDoc}
+     * @throws IllegalArgumentException {@inheritDoc}
+     */
+    ConcurrentNavigableMap<K,V> headMap(K toKey);
+
+    /**
+     * @throws ClassCastException       {@inheritDoc}
+     * @throws NullPointerException     {@inheritDoc}
+     * @throws IllegalArgumentException {@inheritDoc}
+     */
+    ConcurrentNavigableMap<K,V> tailMap(K fromKey);
+
+    /**
+     * Returns a reverse order view of the mappings contained in this map.
+     * The descending map is backed by this map, so changes to the map are
+     * reflected in the descending map, and vice-versa.
+     *
+     * <p>The returned map has an ordering equivalent to
+     * {@link java.util.Collections#reverseOrder(Comparator) Collections.reverseOrder}{@code (comparator())}.
+     * The expression {@code m.descendingMap().descendingMap()} returns a
+     * view of {@code m} essentially equivalent to {@code m}.
+     *
+     * @return a reverse order view of this map
+     */
+    ConcurrentNavigableMap<K,V> descendingMap();
+
+    /**
+     * Returns a {@link NavigableSet} view of the keys contained in this map.
+     * The set's iterator returns the keys in ascending order.
+     * The set is backed by the map, so changes to the map are
+     * reflected in the set, and vice-versa.  The set supports element
+     * removal, which removes the corresponding mapping from the map,
+     * via the {@code Iterator.remove}, {@code Set.remove},
+     * {@code removeAll}, {@code retainAll}, and {@code clear}
+     * operations.  It does not support the {@code add} or {@code addAll}
+     * operations.
+     *
+     * <p>The view's iterators and spliterators are
+     * <a href="package-summary.html#Weakly"><i>weakly consistent</i></a>.
+     *
+     * @return a navigable set view of the keys in this map
+     */
+    NavigableSet<K> navigableKeySet();
+
+    /**
+     * Returns a {@link NavigableSet} view of the keys contained in this map.
+     * The set's iterator returns the keys in ascending order.
+     * The set is backed by the map, so changes to the map are
+     * reflected in the set, and vice-versa.  The set supports element
+     * removal, which removes the corresponding mapping from the map,
+     * via the {@code Iterator.remove}, {@code Set.remove},
+     * {@code removeAll}, {@code retainAll}, and {@code clear}
+     * operations.  It does not support the {@code add} or {@code addAll}
+     * operations.
+     *
+     * <p>The view's iterators and spliterators are
+     * <a href="package-summary.html#Weakly"><i>weakly consistent</i></a>.
+     *
+     * <p>This method is equivalent to method {@code navigableKeySet}.
+     *
+     * @return a navigable set view of the keys in this map
+     */
+    NavigableSet<K> keySet();
+
+    /**
+     * Returns a reverse order {@link NavigableSet} view of the keys contained in this map.
+     * The set's iterator returns the keys in descending order.
+     * The set is backed by the map, so changes to the map are
+     * reflected in the set, and vice-versa.  The set supports element
+     * removal, which removes the corresponding mapping from the map,
+     * via the {@code Iterator.remove}, {@code Set.remove},
+     * {@code removeAll}, {@code retainAll}, and {@code clear}
+     * operations.  It does not support the {@code add} or {@code addAll}
+     * operations.
+     *
+     * <p>The view's iterators and spliterators are
+     * <a href="package-summary.html#Weakly"><i>weakly consistent</i></a>.
+     *
+     * @return a reverse order navigable set view of the keys in this map
+     */
+    NavigableSet<K> descendingKeySet();
+}

src/java.base/share/classes/java/util/concurrent/ConcurrentSkipListSet.java

@@ -0,0 +1,526 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent;
+
+import java.lang.reflect.Field;
+import java.util.AbstractSet;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.Comparator;
+import java.util.Iterator;
+import java.util.Map;
+import java.util.NavigableSet;
+import java.util.Set;
+import java.util.SortedSet;
+import java.util.Spliterator;
+
+/**
+ * A scalable concurrent {@link NavigableSet} implementation based on
+ * a {@link ConcurrentSkipListMap}.  The elements of the set are kept
+ * sorted according to their {@linkplain Comparable natural ordering},
+ * or by a {@link Comparator} provided at set creation time, depending
+ * on which constructor is used.
+ *
+ * <p>This implementation provides expected average <i>log(n)</i> time
+ * cost for the {@code contains}, {@code add}, and {@code remove}
+ * operations and their variants.  Insertion, removal, and access
+ * operations safely execute concurrently by multiple threads.
+ *
+ * <p>Iterators and spliterators are
+ * <a href="package-summary.html#Weakly"><i>weakly consistent</i></a>.
+ *
+ * <p>Ascending ordered views and their iterators are faster than
+ * descending ones.
+ *
+ * <p>Beware that, unlike in most collections, the {@code size}
+ * method is <em>not</em> a constant-time operation. Because of the
+ * asynchronous nature of these sets, determining the current number
+ * of elements requires a traversal of the elements, and so may report
+ * inaccurate results if this collection is modified during traversal.
+ *
+ * <p>Bulk operations that add, remove, or examine multiple elements,
+ * such as {@link #addAll}, {@link #removeIf} or {@link #forEach},
+ * are <em>not</em> guaranteed to be performed atomically.
+ * For example, a {@code forEach} traversal concurrent with an {@code
+ * addAll} operation might observe only some of the added elements.
+ *
+ * <p>This class and its iterators implement all of the
+ * <em>optional</em> methods of the {@link Set} and {@link Iterator}
+ * interfaces. Like most other concurrent collection implementations,
+ * this class does not permit the use of {@code null} elements,
+ * because {@code null} arguments and return values cannot be reliably
+ * distinguished from the absence of elements.
+ *
+ * <p>This class is a member of the
+ * <a href="{@docRoot}/java/util/package-summary.html#CollectionsFramework">
+ * Java Collections Framework</a>.
+ *
+ * @author Doug Lea
+ * @param <E> the type of elements maintained by this set
+ * @since 1.6
+ */
+public class ConcurrentSkipListSet<E>
+    extends AbstractSet<E>
+    implements NavigableSet<E>, Cloneable, java.io.Serializable {
+
+    private static final long serialVersionUID = -2479143111061671589L;
+
+    /**
+     * The underlying map. Uses Boolean.TRUE as value for each
+     * element.  This field is declared final for the sake of thread
+     * safety, which entails some ugliness in clone().
+     */
+    private final ConcurrentNavigableMap<E,Object> m;
+
+    /**
+     * Constructs a new, empty set that orders its elements according to
+     * their {@linkplain Comparable natural ordering}.
+     */
+    public ConcurrentSkipListSet() {
+        m = new ConcurrentSkipListMap<E,Object>();
+    }
+
+    /**
+     * Constructs a new, empty set that orders its elements according to
+     * the specified comparator.
+     *
+     * @param comparator the comparator that will be used to order this set.
+     *        If {@code null}, the {@linkplain Comparable natural
+     *        ordering} of the elements will be used.
+     */
+    public ConcurrentSkipListSet(Comparator<? super E> comparator) {
+        m = new ConcurrentSkipListMap<E,Object>(comparator);
+    }
+
+    /**
+     * Constructs a new set containing the elements in the specified
+     * collection, that orders its elements according to their
+     * {@linkplain Comparable natural ordering}.
+     *
+     * @param c The elements that will comprise the new set
+     * @throws ClassCastException if the elements in {@code c} are
+     *         not {@link Comparable}, or are not mutually comparable
+     * @throws NullPointerException if the specified collection or any
+     *         of its elements are null
+     */
+    public ConcurrentSkipListSet(Collection<? extends E> c) {
+        m = new ConcurrentSkipListMap<E,Object>();
+        addAll(c);
+    }
+
+    /**
+     * Constructs a new set containing the same elements and using the
+     * same ordering as the specified sorted set.
+     *
+     * @param s sorted set whose elements will comprise the new set
+     * @throws NullPointerException if the specified sorted set or any
+     *         of its elements are null
+     */
+    public ConcurrentSkipListSet(SortedSet<E> s) {
+        m = new ConcurrentSkipListMap<E,Object>(s.comparator());
+        addAll(s);
+    }
+
+    /**
+     * For use by submaps
+     */
+    ConcurrentSkipListSet(ConcurrentNavigableMap<E,Object> m) {
+        this.m = m;
+    }
+
+    /**
+     * Returns a shallow copy of this {@code ConcurrentSkipListSet}
+     * instance. (The elements themselves are not cloned.)
+     *
+     * @return a shallow copy of this set
+     */
+    public ConcurrentSkipListSet<E> clone() {
+        try {
+            @SuppressWarnings("unchecked")
+            ConcurrentSkipListSet<E> clone =
+                (ConcurrentSkipListSet<E>) super.clone();
+            clone.setMap(new ConcurrentSkipListMap<E,Object>(m));
+            return clone;
+        } catch (CloneNotSupportedException e) {
+            throw new InternalError();
+        }
+    }
+
+    /* ---------------- Set operations -------------- */
+
+    /**
+     * Returns the number of elements in this set.  If this set
+     * contains more than {@code Integer.MAX_VALUE} elements, it
+     * returns {@code Integer.MAX_VALUE}.
+     *
+     * <p>Beware that, unlike in most collections, this method is
+     * <em>NOT</em> a constant-time operation. Because of the
+     * asynchronous nature of these sets, determining the current
+     * number of elements requires traversing them all to count them.
+     * Additionally, it is possible for the size to change during
+     * execution of this method, in which case the returned result
+     * will be inaccurate. Thus, this method is typically not very
+     * useful in concurrent applications.
+     *
+     * @return the number of elements in this set
+     */
+    public int size() {
+        return m.size();
+    }
+
+    /**
+     * Returns {@code true} if this set contains no elements.
+     * @return {@code true} if this set contains no elements
+     */
+    public boolean isEmpty() {
+        return m.isEmpty();
+    }
+
+    /**
+     * Returns {@code true} if this set contains the specified element.
+     * More formally, returns {@code true} if and only if this set
+     * contains an element {@code e} such that {@code o.equals(e)}.
+     *
+     * @param o object to be checked for containment in this set
+     * @return {@code true} if this set contains the specified element
+     * @throws ClassCastException if the specified element cannot be
+     *         compared with the elements currently in this set
+     * @throws NullPointerException if the specified element is null
+     */
+    public boolean contains(Object o) {
+        return m.containsKey(o);
+    }
+
+    /**
+     * Adds the specified element to this set if it is not already present.
+     * More formally, adds the specified element {@code e} to this set if
+     * the set contains no element {@code e2} such that {@code e.equals(e2)}.
+     * If this set already contains the element, the call leaves the set
+     * unchanged and returns {@code false}.
+     *
+     * @param e element to be added to this set
+     * @return {@code true} if this set did not already contain the
+     *         specified element
+     * @throws ClassCastException if {@code e} cannot be compared
+     *         with the elements currently in this set
+     * @throws NullPointerException if the specified element is null
+     */
+    public boolean add(E e) {
+        return m.putIfAbsent(e, Boolean.TRUE) == null;
+    }
+
+    /**
+     * Removes the specified element from this set if it is present.
+     * More formally, removes an element {@code e} such that
+     * {@code o.equals(e)}, if this set contains such an element.
+     * Returns {@code true} if this set contained the element (or
+     * equivalently, if this set changed as a result of the call).
+     * (This set will not contain the element once the call returns.)
+     *
+     * @param o object to be removed from this set, if present
+     * @return {@code true} if this set contained the specified element
+     * @throws ClassCastException if {@code o} cannot be compared
+     *         with the elements currently in this set
+     * @throws NullPointerException if the specified element is null
+     */
+    public boolean remove(Object o) {
+        return m.remove(o, Boolean.TRUE);
+    }
+
+    /**
+     * Removes all of the elements from this set.
+     */
+    public void clear() {
+        m.clear();
+    }
+
+    /**
+     * Returns an iterator over the elements in this set in ascending order.
+     *
+     * @return an iterator over the elements in this set in ascending order
+     */
+    public Iterator<E> iterator() {
+        return m.navigableKeySet().iterator();
+    }
+
+    /**
+     * Returns an iterator over the elements in this set in descending order.
+     *
+     * @return an iterator over the elements in this set in descending order
+     */
+    public Iterator<E> descendingIterator() {
+        return m.descendingKeySet().iterator();
+    }
+
+
+    /* ---------------- AbstractSet Overrides -------------- */
+
+    /**
+     * Compares the specified object with this set for equality.  Returns
+     * {@code true} if the specified object is also a set, the two sets
+     * have the same size, and every member of the specified set is
+     * contained in this set (or equivalently, every member of this set is
+     * contained in the specified set).  This definition ensures that the
+     * equals method works properly across different implementations of the
+     * set interface.
+     *
+     * @param o the object to be compared for equality with this set
+     * @return {@code true} if the specified object is equal to this set
+     */
+    public boolean equals(Object o) {
+        // Override AbstractSet version to avoid calling size()
+        if (o == this)
+            return true;
+        if (!(o instanceof Set))
+            return false;
+        Collection<?> c = (Collection<?>) o;
+        try {
+            return containsAll(c) && c.containsAll(this);
+        } catch (ClassCastException unused) {
+            return false;
+        } catch (NullPointerException unused) {
+            return false;
+        }
+    }
+
+    /**
+     * Removes from this set all of its elements that are contained in
+     * the specified collection.  If the specified collection is also
+     * a set, this operation effectively modifies this set so that its
+     * value is the <i>asymmetric set difference</i> of the two sets.
+     *
+     * @param  c collection containing elements to be removed from this set
+     * @return {@code true} if this set changed as a result of the call
+     * @throws ClassCastException if the class of an element of this set
+     *         is incompatible with the specified collection
+     * (<a href="{@docRoot}/java/util/Collection.html#optional-restrictions">optional</a>)
+     * @throws NullPointerException if the specified collection or any
+     *         of its elements are null
+     */
+    public boolean removeAll(Collection<?> c) {
+        // Override AbstractSet version to avoid unnecessary call to size()
+        boolean modified = false;
+        for (Object e : c)
+            if (remove(e))
+                modified = true;
+        return modified;
+    }
+
+    /* ---------------- Relational operations -------------- */
+
+    /**
+     * @throws ClassCastException {@inheritDoc}
+     * @throws NullPointerException if the specified element is null
+     */
+    public E lower(E e) {
+        return m.lowerKey(e);
+    }
+
+    /**
+     * @throws ClassCastException {@inheritDoc}
+     * @throws NullPointerException if the specified element is null
+     */
+    public E floor(E e) {
+        return m.floorKey(e);
+    }
+
+    /**
+     * @throws ClassCastException {@inheritDoc}
+     * @throws NullPointerException if the specified element is null
+     */
+    public E ceiling(E e) {
+        return m.ceilingKey(e);
+    }
+
+    /**
+     * @throws ClassCastException {@inheritDoc}
+     * @throws NullPointerException if the specified element is null
+     */
+    public E higher(E e) {
+        return m.higherKey(e);
+    }
+
+    public E pollFirst() {
+        Map.Entry<E,Object> e = m.pollFirstEntry();
+        return (e == null) ? null : e.getKey();
+    }
+
+    public E pollLast() {
+        Map.Entry<E,Object> e = m.pollLastEntry();
+        return (e == null) ? null : e.getKey();
+    }
+
+
+    /* ---------------- SortedSet operations -------------- */
+
+    public Comparator<? super E> comparator() {
+        return m.comparator();
+    }
+
+    /**
+     * @throws java.util.NoSuchElementException {@inheritDoc}
+     */
+    public E first() {
+        return m.firstKey();
+    }
+
+    /**
+     * @throws java.util.NoSuchElementException {@inheritDoc}
+     */
+    public E last() {
+        return m.lastKey();
+    }
+
+    /**
+     * @throws ClassCastException {@inheritDoc}
+     * @throws NullPointerException if {@code fromElement} or
+     *         {@code toElement} is null
+     * @throws IllegalArgumentException {@inheritDoc}
+     */
+    public NavigableSet<E> subSet(E fromElement,
+                                  boolean fromInclusive,
+                                  E toElement,
+                                  boolean toInclusive) {
+        return new ConcurrentSkipListSet<E>
+            (m.subMap(fromElement, fromInclusive,
+                      toElement,   toInclusive));
+    }
+
+    /**
+     * @throws ClassCastException {@inheritDoc}
+     * @throws NullPointerException if {@code toElement} is null
+     * @throws IllegalArgumentException {@inheritDoc}
+     */
+    public NavigableSet<E> headSet(E toElement, boolean inclusive) {
+        return new ConcurrentSkipListSet<E>(m.headMap(toElement, inclusive));
+    }
+
+    /**
+     * @throws ClassCastException {@inheritDoc}
+     * @throws NullPointerException if {@code fromElement} is null
+     * @throws IllegalArgumentException {@inheritDoc}
+     */
+    public NavigableSet<E> tailSet(E fromElement, boolean inclusive) {
+        return new ConcurrentSkipListSet<E>(m.tailMap(fromElement, inclusive));
+    }
+
+    /**
+     * @throws ClassCastException {@inheritDoc}
+     * @throws NullPointerException if {@code fromElement} or
+     *         {@code toElement} is null
+     * @throws IllegalArgumentException {@inheritDoc}
+     */
+    public NavigableSet<E> subSet(E fromElement, E toElement) {
+        return subSet(fromElement, true, toElement, false);
+    }
+
+    /**
+     * @throws ClassCastException {@inheritDoc}
+     * @throws NullPointerException if {@code toElement} is null
+     * @throws IllegalArgumentException {@inheritDoc}
+     */
+    public NavigableSet<E> headSet(E toElement) {
+        return headSet(toElement, false);
+    }
+
+    /**
+     * @throws ClassCastException {@inheritDoc}
+     * @throws NullPointerException if {@code fromElement} is null
+     * @throws IllegalArgumentException {@inheritDoc}
+     */
+    public NavigableSet<E> tailSet(E fromElement) {
+        return tailSet(fromElement, true);
+    }
+
+    /**
+     * Returns a reverse order view of the elements contained in this set.
+     * The descending set is backed by this set, so changes to the set are
+     * reflected in the descending set, and vice-versa.
+     *
+     * <p>The returned set has an ordering equivalent to
+     * {@link Collections#reverseOrder(Comparator) Collections.reverseOrder}{@code (comparator())}.
+     * The expression {@code s.descendingSet().descendingSet()} returns a
+     * view of {@code s} essentially equivalent to {@code s}.
+     *
+     * @return a reverse order view of this set
+     */
+    public NavigableSet<E> descendingSet() {
+        return new ConcurrentSkipListSet<E>(m.descendingMap());
+    }
+
+    /**
+     * Returns a {@link Spliterator} over the elements in this set.
+     *
+     * <p>The {@code Spliterator} reports {@link Spliterator#CONCURRENT},
+     * {@link Spliterator#NONNULL}, {@link Spliterator#DISTINCT},
+     * {@link Spliterator#SORTED} and {@link Spliterator#ORDERED}, with an
+     * encounter order that is ascending order.  Overriding implementations
+     * should document the reporting of additional characteristic values.
+     *
+     * <p>The {@linkplain Spliterator#getComparator() spliterator's comparator}
+     * is {@code null} if the {@linkplain #comparator() set's comparator}
+     * is {@code null}.
+     * Otherwise, the spliterator's comparator is the same as or imposes the
+     * same total ordering as the set's comparator.
+     *
+     * @return a {@code Spliterator} over the elements in this set
+     * @since 1.8
+     */
+    public Spliterator<E> spliterator() {
+        return (m instanceof ConcurrentSkipListMap)
+            ? ((ConcurrentSkipListMap<E,?>)m).keySpliterator()
+            : ((ConcurrentSkipListMap.SubMap<E,?>)m).new SubMapKeyIterator();
+    }
+
+    /** Initializes map field; for use in clone. */
+    private void setMap(ConcurrentNavigableMap<E,Object> map) {
+        Field mapField = java.security.AccessController.doPrivileged(
+            (java.security.PrivilegedAction<Field>) () -> {
+                try {
+                    Field f = ConcurrentSkipListSet.class
+                        .getDeclaredField("m");
+                    f.setAccessible(true);
+                    return f;
+                } catch (ReflectiveOperationException e) {
+                    throw new Error(e);
+                }});
+        try {
+            mapField.set(this, map);
+        } catch (IllegalAccessException e) {
+            throw new Error(e);
+        }
+    }
+}

src/java.base/share/classes/java/util/concurrent/CopyOnWriteArraySet.java

@@ -0,0 +1,447 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent;
+
+import java.util.AbstractSet;
+import java.util.Collection;
+import java.util.Iterator;
+import java.util.Objects;
+import java.util.Set;
+import java.util.Spliterator;
+import java.util.Spliterators;
+import java.util.function.Consumer;
+import java.util.function.Predicate;
+
+/**
+ * A {@link Set} that uses an internal {@link CopyOnWriteArrayList}
+ * for all of its operations.  Thus, it shares the same basic properties:
+ * <ul>
+ *  <li>It is best suited for applications in which set sizes generally
+ *       stay small, read-only operations
+ *       vastly outnumber mutative operations, and you need
+ *       to prevent interference among threads during traversal.
+ *  <li>It is thread-safe.
+ *  <li>Mutative operations ({@code add}, {@code set}, {@code remove}, etc.)
+ *      are expensive since they usually entail copying the entire underlying
+ *      array.
+ *  <li>Iterators do not support the mutative {@code remove} operation.
+ *  <li>Traversal via iterators is fast and cannot encounter
+ *      interference from other threads. Iterators rely on
+ *      unchanging snapshots of the array at the time the iterators were
+ *      constructed.
+ * </ul>
+ *
+ * <p><b>Sample Usage.</b> The following code sketch uses a
+ * copy-on-write set to maintain a set of Handler objects that
+ * perform some action upon state updates.
+ *
+ * <pre> {@code
+ * class Handler { void handle(); ... }
+ *
+ * class X {
+ *   private final CopyOnWriteArraySet<Handler> handlers
+ *     = new CopyOnWriteArraySet<>();
+ *   public void addHandler(Handler h) { handlers.add(h); }
+ *
+ *   private long internalState;
+ *   private synchronized void changeState() { internalState = ...; }
+ *
+ *   public void update() {
+ *     changeState();
+ *     for (Handler handler : handlers)
+ *       handler.handle();
+ *   }
+ * }}</pre>
+ *
+ * <p>This class is a member of the
+ * <a href="{@docRoot}/java/util/package-summary.html#CollectionsFramework">
+ * Java Collections Framework</a>.
+ *
+ * @see CopyOnWriteArrayList
+ * @since 1.5
+ * @author Doug Lea
+ * @param <E> the type of elements held in this set
+ */
+public class CopyOnWriteArraySet<E> extends AbstractSet<E>
+        implements java.io.Serializable {
+    private static final long serialVersionUID = 5457747651344034263L;
+
+    private final CopyOnWriteArrayList<E> al;
+
+    /**
+     * Creates an empty set.
+     */
+    public CopyOnWriteArraySet() {
+        al = new CopyOnWriteArrayList<E>();
+    }
+
+    /**
+     * Creates a set containing all of the elements of the specified
+     * collection.
+     *
+     * @param c the collection of elements to initially contain
+     * @throws NullPointerException if the specified collection is null
+     */
+    public CopyOnWriteArraySet(Collection<? extends E> c) {
+        if (c.getClass() == CopyOnWriteArraySet.class) {
+            @SuppressWarnings("unchecked") CopyOnWriteArraySet<E> cc =
+                (CopyOnWriteArraySet<E>)c;
+            al = new CopyOnWriteArrayList<E>(cc.al);
+        }
+        else {
+            al = new CopyOnWriteArrayList<E>();
+            al.addAllAbsent(c);
+        }
+    }
+
+    /**
+     * Returns the number of elements in this set.
+     *
+     * @return the number of elements in this set
+     */
+    public int size() {
+        return al.size();
+    }
+
+    /**
+     * Returns {@code true} if this set contains no elements.
+     *
+     * @return {@code true} if this set contains no elements
+     */
+    public boolean isEmpty() {
+        return al.isEmpty();
+    }
+
+    /**
+     * Returns {@code true} if this set contains the specified element.
+     * More formally, returns {@code true} if and only if this set
+     * contains an element {@code e} such that {@code Objects.equals(o, e)}.
+     *
+     * @param o element whose presence in this set is to be tested
+     * @return {@code true} if this set contains the specified element
+     */
+    public boolean contains(Object o) {
+        return al.contains(o);
+    }
+
+    /**
+     * Returns an array containing all of the elements in this set.
+     * If this set makes any guarantees as to what order its elements
+     * are returned by its iterator, this method must return the
+     * elements in the same order.
+     *
+     * <p>The returned array will be "safe" in that no references to it
+     * are maintained by this set.  (In other words, this method must
+     * allocate a new array even if this set is backed by an array).
+     * The caller is thus free to modify the returned array.
+     *
+     * <p>This method acts as bridge between array-based and collection-based
+     * APIs.
+     *
+     * @return an array containing all the elements in this set
+     */
+    public Object[] toArray() {
+        return al.toArray();
+    }
+
+    /**
+     * Returns an array containing all of the elements in this set; the
+     * runtime type of the returned array is that of the specified array.
+     * If the set fits in the specified array, it is returned therein.
+     * Otherwise, a new array is allocated with the runtime type of the
+     * specified array and the size of this set.
+     *
+     * <p>If this set fits in the specified array with room to spare
+     * (i.e., the array has more elements than this set), the element in
+     * the array immediately following the end of the set is set to
+     * {@code null}.  (This is useful in determining the length of this
+     * set <i>only</i> if the caller knows that this set does not contain
+     * any null elements.)
+     *
+     * <p>If this set makes any guarantees as to what order its elements
+     * are returned by its iterator, this method must return the elements
+     * in the same order.
+     *
+     * <p>Like the {@link #toArray()} method, this method acts as bridge between
+     * array-based and collection-based APIs.  Further, this method allows
+     * precise control over the runtime type of the output array, and may,
+     * under certain circumstances, be used to save allocation costs.
+     *
+     * <p>Suppose {@code x} is a set known to contain only strings.
+     * The following code can be used to dump the set into a newly allocated
+     * array of {@code String}:
+     *
+     * <pre> {@code String[] y = x.toArray(new String[0]);}</pre>
+     *
+     * Note that {@code toArray(new Object[0])} is identical in function to
+     * {@code toArray()}.
+     *
+     * @param a the array into which the elements of this set are to be
+     *        stored, if it is big enough; otherwise, a new array of the same
+     *        runtime type is allocated for this purpose.
+     * @return an array containing all the elements in this set
+     * @throws ArrayStoreException if the runtime type of the specified array
+     *         is not a supertype of the runtime type of every element in this
+     *         set
+     * @throws NullPointerException if the specified array is null
+     */
+    public <T> T[] toArray(T[] a) {
+        return al.toArray(a);
+    }
+
+    /**
+     * Removes all of the elements from this set.
+     * The set will be empty after this call returns.
+     */
+    public void clear() {
+        al.clear();
+    }
+
+    /**
+     * Removes the specified element from this set if it is present.
+     * More formally, removes an element {@code e} such that
+     * {@code Objects.equals(o, e)}, if this set contains such an element.
+     * Returns {@code true} if this set contained the element (or
+     * equivalently, if this set changed as a result of the call).
+     * (This set will not contain the element once the call returns.)
+     *
+     * @param o object to be removed from this set, if present
+     * @return {@code true} if this set contained the specified element
+     */
+    public boolean remove(Object o) {
+        return al.remove(o);
+    }
+
+    /**
+     * Adds the specified element to this set if it is not already present.
+     * More formally, adds the specified element {@code e} to this set if
+     * the set contains no element {@code e2} such that
+     * {@code Objects.equals(e, e2)}.
+     * If this set already contains the element, the call leaves the set
+     * unchanged and returns {@code false}.
+     *
+     * @param e element to be added to this set
+     * @return {@code true} if this set did not already contain the specified
+     *         element
+     */
+    public boolean add(E e) {
+        return al.addIfAbsent(e);
+    }
+
+    /**
+     * Returns {@code true} if this set contains all of the elements of the
+     * specified collection.  If the specified collection is also a set, this
+     * method returns {@code true} if it is a <i>subset</i> of this set.
+     *
+     * @param  c collection to be checked for containment in this set
+     * @return {@code true} if this set contains all of the elements of the
+     *         specified collection
+     * @throws NullPointerException if the specified collection is null
+     * @see #contains(Object)
+     */
+    public boolean containsAll(Collection<?> c) {
+        return (c instanceof Set)
+            ? compareSets(al.getArray(), (Set<?>) c) >= 0
+            : al.containsAll(c);
+    }
+
+    /**
+     * Tells whether the objects in snapshot (regarded as a set) are a
+     * superset of the given set.
+     *
+     * @return -1 if snapshot is not a superset, 0 if the two sets
+     * contain precisely the same elements, and 1 if snapshot is a
+     * proper superset of the given set
+     */
+    private static int compareSets(Object[] snapshot, Set<?> set) {
+        // Uses O(n^2) algorithm, that is only appropriate for small
+        // sets, which CopyOnWriteArraySets should be.
+        //
+        // Optimize up to O(n) if the two sets share a long common prefix,
+        // as might happen if one set was created as a copy of the other set.
+
+        final int len = snapshot.length;
+        // Mark matched elements to avoid re-checking
+        final boolean[] matched = new boolean[len];
+
+        // j is the largest int with matched[i] true for { i | 0 <= i < j }
+        int j = 0;
+        outer: for (Object x : set) {
+            for (int i = j; i < len; i++) {
+                if (!matched[i] && Objects.equals(x, snapshot[i])) {
+                    matched[i] = true;
+                    if (i == j)
+                        do { j++; } while (j < len && matched[j]);
+                    continue outer;
+                }
+            }
+            return -1;
+        }
+        return (j == len) ? 0 : 1;
+    }
+
+    /**
+     * Adds all of the elements in the specified collection to this set if
+     * they're not already present.  If the specified collection is also a
+     * set, the {@code addAll} operation effectively modifies this set so
+     * that its value is the <i>union</i> of the two sets.  The behavior of
+     * this operation is undefined if the specified collection is modified
+     * while the operation is in progress.
+     *
+     * @param  c collection containing elements to be added to this set
+     * @return {@code true} if this set changed as a result of the call
+     * @throws NullPointerException if the specified collection is null
+     * @see #add(Object)
+     */
+    public boolean addAll(Collection<? extends E> c) {
+        return al.addAllAbsent(c) > 0;
+    }
+
+    /**
+     * Removes from this set all of its elements that are contained in the
+     * specified collection.  If the specified collection is also a set,
+     * this operation effectively modifies this set so that its value is the
+     * <i>asymmetric set difference</i> of the two sets.
+     *
+     * @param  c collection containing elements to be removed from this set
+     * @return {@code true} if this set changed as a result of the call
+     * @throws ClassCastException if the class of an element of this set
+     *         is incompatible with the specified collection
+     * (<a href="{@docRoot}/java/util/Collection.html#optional-restrictions">optional</a>)
+     * @throws NullPointerException if this set contains a null element and the
+     *         specified collection does not permit null elements
+     * (<a href="{@docRoot}/java/util/Collection.html#optional-restrictions">optional</a>),
+     *         or if the specified collection is null
+     * @see #remove(Object)
+     */
+    public boolean removeAll(Collection<?> c) {
+        return al.removeAll(c);
+    }
+
+    /**
+     * Retains only the elements in this set that are contained in the
+     * specified collection.  In other words, removes from this set all of
+     * its elements that are not contained in the specified collection.  If
+     * the specified collection is also a set, this operation effectively
+     * modifies this set so that its value is the <i>intersection</i> of the
+     * two sets.
+     *
+     * @param  c collection containing elements to be retained in this set
+     * @return {@code true} if this set changed as a result of the call
+     * @throws ClassCastException if the class of an element of this set
+     *         is incompatible with the specified collection
+     * (<a href="{@docRoot}/java/util/Collection.html#optional-restrictions">optional</a>)
+     * @throws NullPointerException if this set contains a null element and the
+     *         specified collection does not permit null elements
+     * (<a href="{@docRoot}/java/util/Collection.html#optional-restrictions">optional</a>),
+     *         or if the specified collection is null
+     * @see #remove(Object)
+     */
+    public boolean retainAll(Collection<?> c) {
+        return al.retainAll(c);
+    }
+
+    /**
+     * Returns an iterator over the elements contained in this set
+     * in the order in which these elements were added.
+     *
+     * <p>The returned iterator provides a snapshot of the state of the set
+     * when the iterator was constructed. No synchronization is needed while
+     * traversing the iterator. The iterator does <em>NOT</em> support the
+     * {@code remove} method.
+     *
+     * @return an iterator over the elements in this set
+     */
+    public Iterator<E> iterator() {
+        return al.iterator();
+    }
+
+    /**
+     * Compares the specified object with this set for equality.
+     * Returns {@code true} if the specified object is the same object
+     * as this object, or if it is also a {@link Set} and the elements
+     * returned by an {@linkplain Set#iterator() iterator} over the
+     * specified set are the same as the elements returned by an
+     * iterator over this set.  More formally, the two iterators are
+     * considered to return the same elements if they return the same
+     * number of elements and for every element {@code e1} returned by
+     * the iterator over the specified set, there is an element
+     * {@code e2} returned by the iterator over this set such that
+     * {@code Objects.equals(e1, e2)}.
+     *
+     * @param o object to be compared for equality with this set
+     * @return {@code true} if the specified object is equal to this set
+     */
+    public boolean equals(Object o) {
+        return (o == this)
+            || ((o instanceof Set)
+                && compareSets(al.getArray(), (Set<?>) o) == 0);
+    }
+
+    /**
+     * @throws NullPointerException {@inheritDoc}
+     */
+    public boolean removeIf(Predicate<? super E> filter) {
+        return al.removeIf(filter);
+    }
+
+    /**
+     * @throws NullPointerException {@inheritDoc}
+     */
+    public void forEach(Consumer<? super E> action) {
+        al.forEach(action);
+    }
+
+    /**
+     * Returns a {@link Spliterator} over the elements in this set in the order
+     * in which these elements were added.
+     *
+     * <p>The {@code Spliterator} reports {@link Spliterator#IMMUTABLE},
+     * {@link Spliterator#DISTINCT}, {@link Spliterator#SIZED}, and
+     * {@link Spliterator#SUBSIZED}.
+     *
+     * <p>The spliterator provides a snapshot of the state of the set
+     * when the spliterator was constructed. No synchronization is needed while
+     * operating on the spliterator.
+     *
+     * @return a {@code Spliterator} over the elements in this set
+     * @since 1.8
+     */
+    public Spliterator<E> spliterator() {
+        return Spliterators.spliterator
+            (al.getArray(), Spliterator.IMMUTABLE | Spliterator.DISTINCT);
+    }
+}

src/java.base/share/classes/java/util/concurrent/CountDownLatch.java

@@ -0,0 +1,316 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent;
+
+import java.util.concurrent.locks.AbstractQueuedSynchronizer;
+
+/**
+ * A synchronization aid that allows one or more threads to wait until
+ * a set of operations being performed in other threads completes.
+ *
+ * <p>A {@code CountDownLatch} is initialized with a given <em>count</em>.
+ * The {@link #await await} methods block until the current count reaches
+ * zero due to invocations of the {@link #countDown} method, after which
+ * all waiting threads are released and any subsequent invocations of
+ * {@link #await await} return immediately.  This is a one-shot phenomenon
+ * -- the count cannot be reset.  If you need a version that resets the
+ * count, consider using a {@link CyclicBarrier}.
+ *
+ * <p>A {@code CountDownLatch} is a versatile synchronization tool
+ * and can be used for a number of purposes.  A
+ * {@code CountDownLatch} initialized with a count of one serves as a
+ * simple on/off latch, or gate: all threads invoking {@link #await await}
+ * wait at the gate until it is opened by a thread invoking {@link
+ * #countDown}.  A {@code CountDownLatch} initialized to <em>N</em>
+ * can be used to make one thread wait until <em>N</em> threads have
+ * completed some action, or some action has been completed N times.
+ *
+ * <p>A useful property of a {@code CountDownLatch} is that it
+ * doesn't require that threads calling {@code countDown} wait for
+ * the count to reach zero before proceeding, it simply prevents any
+ * thread from proceeding past an {@link #await await} until all
+ * threads could pass.
+ *
+ * <p><b>Sample usage:</b> Here is a pair of classes in which a group
+ * of worker threads use two countdown latches:
+ * <ul>
+ * <li>The first is a start signal that prevents any worker from proceeding
+ * until the driver is ready for them to proceed;
+ * <li>The second is a completion signal that allows the driver to wait
+ * until all workers have completed.
+ * </ul>
+ *
+ * <pre> {@code
+ * class Driver { // ...
+ *   void main() throws InterruptedException {
+ *     CountDownLatch startSignal = new CountDownLatch(1);
+ *     CountDownLatch doneSignal = new CountDownLatch(N);
+ *
+ *     for (int i = 0; i < N; ++i) // create and start threads
+ *       new Thread(new Worker(startSignal, doneSignal)).start();
+ *
+ *     doSomethingElse();            // don't let run yet
+ *     startSignal.countDown();      // let all threads proceed
+ *     doSomethingElse();
+ *     doneSignal.await();           // wait for all to finish
+ *   }
+ * }
+ *
+ * class Worker implements Runnable {
+ *   private final CountDownLatch startSignal;
+ *   private final CountDownLatch doneSignal;
+ *   Worker(CountDownLatch startSignal, CountDownLatch doneSignal) {
+ *     this.startSignal = startSignal;
+ *     this.doneSignal = doneSignal;
+ *   }
+ *   public void run() {
+ *     try {
+ *       startSignal.await();
+ *       doWork();
+ *       doneSignal.countDown();
+ *     } catch (InterruptedException ex) {} // return;
+ *   }
+ *
+ *   void doWork() { ... }
+ * }}</pre>
+ *
+ * <p>Another typical usage would be to divide a problem into N parts,
+ * describe each part with a Runnable that executes that portion and
+ * counts down on the latch, and queue all the Runnables to an
+ * Executor.  When all sub-parts are complete, the coordinating thread
+ * will be able to pass through await. (When threads must repeatedly
+ * count down in this way, instead use a {@link CyclicBarrier}.)
+ *
+ * <pre> {@code
+ * class Driver2 { // ...
+ *   void main() throws InterruptedException {
+ *     CountDownLatch doneSignal = new CountDownLatch(N);
+ *     Executor e = ...
+ *
+ *     for (int i = 0; i < N; ++i) // create and start threads
+ *       e.execute(new WorkerRunnable(doneSignal, i));
+ *
+ *     doneSignal.await();           // wait for all to finish
+ *   }
+ * }
+ *
+ * class WorkerRunnable implements Runnable {
+ *   private final CountDownLatch doneSignal;
+ *   private final int i;
+ *   WorkerRunnable(CountDownLatch doneSignal, int i) {
+ *     this.doneSignal = doneSignal;
+ *     this.i = i;
+ *   }
+ *   public void run() {
+ *     try {
+ *       doWork(i);
+ *       doneSignal.countDown();
+ *     } catch (InterruptedException ex) {} // return;
+ *   }
+ *
+ *   void doWork() { ... }
+ * }}</pre>
+ *
+ * <p>Memory consistency effects: Until the count reaches
+ * zero, actions in a thread prior to calling
+ * {@code countDown()}
+ * <a href="package-summary.html#MemoryVisibility"><i>happen-before</i></a>
+ * actions following a successful return from a corresponding
+ * {@code await()} in another thread.
+ *
+ * @since 1.5
+ * @author Doug Lea
+ */
+public class CountDownLatch {
+    /**
+     * Synchronization control For CountDownLatch.
+     * Uses AQS state to represent count.
+     */
+    private static final class Sync extends AbstractQueuedSynchronizer {
+        private static final long serialVersionUID = 4982264981922014374L;
+
+        Sync(int count) {
+            setState(count);
+        }
+
+        int getCount() {
+            return getState();
+        }
+
+        protected int tryAcquireShared(int acquires) {
+            return (getState() == 0) ? 1 : -1;
+        }
+
+        protected boolean tryReleaseShared(int releases) {
+            // Decrement count; signal when transition to zero
+            for (;;) {
+                int c = getState();
+                if (c == 0)
+                    return false;
+                int nextc = c - 1;
+                if (compareAndSetState(c, nextc))
+                    return nextc == 0;
+            }
+        }
+    }
+
+    private final Sync sync;
+
+    /**
+     * Constructs a {@code CountDownLatch} initialized with the given count.
+     *
+     * @param count the number of times {@link #countDown} must be invoked
+     *        before threads can pass through {@link #await}
+     * @throws IllegalArgumentException if {@code count} is negative
+     */
+    public CountDownLatch(int count) {
+        if (count < 0) throw new IllegalArgumentException("count < 0");
+        this.sync = new Sync(count);
+    }
+
+    /**
+     * Causes the current thread to wait until the latch has counted down to
+     * zero, unless the thread is {@linkplain Thread#interrupt interrupted}.
+     *
+     * <p>If the current count is zero then this method returns immediately.
+     *
+     * <p>If the current count is greater than zero then the current
+     * thread becomes disabled for thread scheduling purposes and lies
+     * dormant until one of two things happen:
+     * <ul>
+     * <li>The count reaches zero due to invocations of the
+     * {@link #countDown} method; or
+     * <li>Some other thread {@linkplain Thread#interrupt interrupts}
+     * the current thread.
+     * </ul>
+     *
+     * <p>If the current thread:
+     * <ul>
+     * <li>has its interrupted status set on entry to this method; or
+     * <li>is {@linkplain Thread#interrupt interrupted} while waiting,
+     * </ul>
+     * then {@link InterruptedException} is thrown and the current thread's
+     * interrupted status is cleared.
+     *
+     * @throws InterruptedException if the current thread is interrupted
+     *         while waiting
+     */
+    public void await() throws InterruptedException {
+        sync.acquireSharedInterruptibly(1);
+    }
+
+    /**
+     * Causes the current thread to wait until the latch has counted down to
+     * zero, unless the thread is {@linkplain Thread#interrupt interrupted},
+     * or the specified waiting time elapses.
+     *
+     * <p>If the current count is zero then this method returns immediately
+     * with the value {@code true}.
+     *
+     * <p>If the current count is greater than zero then the current
+     * thread becomes disabled for thread scheduling purposes and lies
+     * dormant until one of three things happen:
+     * <ul>
+     * <li>The count reaches zero due to invocations of the
+     * {@link #countDown} method; or
+     * <li>Some other thread {@linkplain Thread#interrupt interrupts}
+     * the current thread; or
+     * <li>The specified waiting time elapses.
+     * </ul>
+     *
+     * <p>If the count reaches zero then the method returns with the
+     * value {@code true}.
+     *
+     * <p>If the current thread:
+     * <ul>
+     * <li>has its interrupted status set on entry to this method; or
+     * <li>is {@linkplain Thread#interrupt interrupted} while waiting,
+     * </ul>
+     * then {@link InterruptedException} is thrown and the current thread's
+     * interrupted status is cleared.
+     *
+     * <p>If the specified waiting time elapses then the value {@code false}
+     * is returned.  If the time is less than or equal to zero, the method
+     * will not wait at all.
+     *
+     * @param timeout the maximum time to wait
+     * @param unit the time unit of the {@code timeout} argument
+     * @return {@code true} if the count reached zero and {@code false}
+     *         if the waiting time elapsed before the count reached zero
+     * @throws InterruptedException if the current thread is interrupted
+     *         while waiting
+     */
+    public boolean await(long timeout, TimeUnit unit)
+        throws InterruptedException {
+        return sync.tryAcquireSharedNanos(1, unit.toNanos(timeout));
+    }
+
+    /**
+     * Decrements the count of the latch, releasing all waiting threads if
+     * the count reaches zero.
+     *
+     * <p>If the current count is greater than zero then it is decremented.
+     * If the new count is zero then all waiting threads are re-enabled for
+     * thread scheduling purposes.
+     *
+     * <p>If the current count equals zero then nothing happens.
+     */
+    public void countDown() {
+        sync.releaseShared(1);
+    }
+
+    /**
+     * Returns the current count.
+     *
+     * <p>This method is typically used for debugging and testing purposes.
+     *
+     * @return the current count
+     */
+    public long getCount() {
+        return sync.getCount();
+    }
+
+    /**
+     * Returns a string identifying this latch, as well as its state.
+     * The state, in brackets, includes the String {@code "Count ="}
+     * followed by the current count.
+     *
+     * @return a string identifying this latch, as well as its state
+     */
+    public String toString() {
+        return super.toString() + "[Count = " + sync.getCount() + "]";
+    }
+}

src/java.base/share/classes/java/util/concurrent/CountedCompleter.java

@@ -0,0 +1,781 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent;
+
+import java.lang.invoke.MethodHandles;
+import java.lang.invoke.VarHandle;
+
+/**
+ * A {@link ForkJoinTask} with a completion action performed when
+ * triggered and there are no remaining pending actions.
+ * CountedCompleters are in general more robust in the
+ * presence of subtask stalls and blockage than are other forms of
+ * ForkJoinTasks, but are less intuitive to program.  Uses of
+ * CountedCompleter are similar to those of other completion based
+ * components (such as {@link java.nio.channels.CompletionHandler})
+ * except that multiple <em>pending</em> completions may be necessary
+ * to trigger the completion action {@link #onCompletion(CountedCompleter)},
+ * not just one.
+ * Unless initialized otherwise, the {@linkplain #getPendingCount pending
+ * count} starts at zero, but may be (atomically) changed using
+ * methods {@link #setPendingCount}, {@link #addToPendingCount}, and
+ * {@link #compareAndSetPendingCount}. Upon invocation of {@link
+ * #tryComplete}, if the pending action count is nonzero, it is
+ * decremented; otherwise, the completion action is performed, and if
+ * this completer itself has a completer, the process is continued
+ * with its completer.  As is the case with related synchronization
+ * components such as {@link Phaser} and {@link Semaphore}, these methods
+ * affect only internal counts; they do not establish any further
+ * internal bookkeeping. In particular, the identities of pending
+ * tasks are not maintained. As illustrated below, you can create
+ * subclasses that do record some or all pending tasks or their
+ * results when needed.  As illustrated below, utility methods
+ * supporting customization of completion traversals are also
+ * provided. However, because CountedCompleters provide only basic
+ * synchronization mechanisms, it may be useful to create further
+ * abstract subclasses that maintain linkages, fields, and additional
+ * support methods appropriate for a set of related usages.
+ *
+ * <p>A concrete CountedCompleter class must define method {@link
+ * #compute}, that should in most cases (as illustrated below), invoke
+ * {@code tryComplete()} once before returning. The class may also
+ * optionally override method {@link #onCompletion(CountedCompleter)}
+ * to perform an action upon normal completion, and method
+ * {@link #onExceptionalCompletion(Throwable, CountedCompleter)} to
+ * perform an action upon any exception.
+ *
+ * <p>CountedCompleters most often do not bear results, in which case
+ * they are normally declared as {@code CountedCompleter<Void>}, and
+ * will always return {@code null} as a result value.  In other cases,
+ * you should override method {@link #getRawResult} to provide a
+ * result from {@code join(), invoke()}, and related methods.  In
+ * general, this method should return the value of a field (or a
+ * function of one or more fields) of the CountedCompleter object that
+ * holds the result upon completion. Method {@link #setRawResult} by
+ * default plays no role in CountedCompleters.  It is possible, but
+ * rarely applicable, to override this method to maintain other
+ * objects or fields holding result data.
+ *
+ * <p>A CountedCompleter that does not itself have a completer (i.e.,
+ * one for which {@link #getCompleter} returns {@code null}) can be
+ * used as a regular ForkJoinTask with this added functionality.
+ * However, any completer that in turn has another completer serves
+ * only as an internal helper for other computations, so its own task
+ * status (as reported in methods such as {@link ForkJoinTask#isDone})
+ * is arbitrary; this status changes only upon explicit invocations of
+ * {@link #complete}, {@link ForkJoinTask#cancel},
+ * {@link ForkJoinTask#completeExceptionally(Throwable)} or upon
+ * exceptional completion of method {@code compute}. Upon any
+ * exceptional completion, the exception may be relayed to a task's
+ * completer (and its completer, and so on), if one exists and it has
+ * not otherwise already completed. Similarly, cancelling an internal
+ * CountedCompleter has only a local effect on that completer, so is
+ * not often useful.
+ *
+ * <p><b>Sample Usages.</b>
+ *
+ * <p><b>Parallel recursive decomposition.</b> CountedCompleters may
+ * be arranged in trees similar to those often used with {@link
+ * RecursiveAction}s, although the constructions involved in setting
+ * them up typically vary. Here, the completer of each task is its
+ * parent in the computation tree. Even though they entail a bit more
+ * bookkeeping, CountedCompleters may be better choices when applying
+ * a possibly time-consuming operation (that cannot be further
+ * subdivided) to each element of an array or collection; especially
+ * when the operation takes a significantly different amount of time
+ * to complete for some elements than others, either because of
+ * intrinsic variation (for example I/O) or auxiliary effects such as
+ * garbage collection.  Because CountedCompleters provide their own
+ * continuations, other tasks need not block waiting to perform them.
+ *
+ * <p>For example, here is an initial version of a utility method that
+ * uses divide-by-two recursive decomposition to divide work into
+ * single pieces (leaf tasks). Even when work is split into individual
+ * calls, tree-based techniques are usually preferable to directly
+ * forking leaf tasks, because they reduce inter-thread communication
+ * and improve load balancing. In the recursive case, the second of
+ * each pair of subtasks to finish triggers completion of their parent
+ * (because no result combination is performed, the default no-op
+ * implementation of method {@code onCompletion} is not overridden).
+ * The utility method sets up the root task and invokes it (here,
+ * implicitly using the {@link ForkJoinPool#commonPool()}).  It is
+ * straightforward and reliable (but not optimal) to always set the
+ * pending count to the number of child tasks and call {@code
+ * tryComplete()} immediately before returning.
+ *
+ * <pre> {@code
+ * public static <E> void forEach(E[] array, Consumer<E> action) {
+ *   class Task extends CountedCompleter<Void> {
+ *     final int lo, hi;
+ *     Task(Task parent, int lo, int hi) {
+ *       super(parent); this.lo = lo; this.hi = hi;
+ *     }
+ *
+ *     public void compute() {
+ *       if (hi - lo >= 2) {
+ *         int mid = (lo + hi) >>> 1;
+ *         // must set pending count before fork
+ *         setPendingCount(2);
+ *         new Task(this, mid, hi).fork(); // right child
+ *         new Task(this, lo, mid).fork(); // left child
+ *       }
+ *       else if (hi > lo)
+ *         action.accept(array[lo]);
+ *       tryComplete();
+ *     }
+ *   }
+ *   new Task(null, 0, array.length).invoke();
+ * }}</pre>
+ *
+ * This design can be improved by noticing that in the recursive case,
+ * the task has nothing to do after forking its right task, so can
+ * directly invoke its left task before returning. (This is an analog
+ * of tail recursion removal.)  Also, when the last action in a task
+ * is to fork or invoke a subtask (a "tail call"), the call to {@code
+ * tryComplete()} can be optimized away, at the cost of making the
+ * pending count look "off by one".
+ *
+ * <pre> {@code
+ *     public void compute() {
+ *       if (hi - lo >= 2) {
+ *         int mid = (lo + hi) >>> 1;
+ *         setPendingCount(1); // looks off by one, but correct!
+ *         new Task(this, mid, hi).fork(); // right child
+ *         new Task(this, lo, mid).compute(); // direct invoke
+ *       } else {
+ *         if (hi > lo)
+ *           action.accept(array[lo]);
+ *         tryComplete();
+ *       }
+ *     }}</pre>
+ *
+ * As a further optimization, notice that the left task need not even exist.
+ * Instead of creating a new one, we can continue using the original task,
+ * and add a pending count for each fork.  Additionally, because no task
+ * in this tree implements an {@link #onCompletion(CountedCompleter)} method,
+ * {@code tryComplete} can be replaced with {@link #propagateCompletion}.
+ *
+ * <pre> {@code
+ *     public void compute() {
+ *       int n = hi - lo;
+ *       for (; n >= 2; n /= 2) {
+ *         addToPendingCount(1);
+ *         new Task(this, lo + n/2, lo + n).fork();
+ *       }
+ *       if (n > 0)
+ *         action.accept(array[lo]);
+ *       propagateCompletion();
+ *     }}</pre>
+ *
+ * When pending counts can be precomputed, they can be established in
+ * the constructor:
+ *
+ * <pre> {@code
+ * public static <E> void forEach(E[] array, Consumer<E> action) {
+ *   class Task extends CountedCompleter<Void> {
+ *     final int lo, hi;
+ *     Task(Task parent, int lo, int hi) {
+ *       super(parent, 31 - Integer.numberOfLeadingZeros(hi - lo));
+ *       this.lo = lo; this.hi = hi;
+ *     }
+ *
+ *     public void compute() {
+ *       for (int n = hi - lo; n >= 2; n /= 2)
+ *         new Task(this, lo + n/2, lo + n).fork();
+ *       action.accept(array[lo]);
+ *       propagateCompletion();
+ *     }
+ *   }
+ *   if (array.length > 0)
+ *     new Task(null, 0, array.length).invoke();
+ * }}</pre>
+ *
+ * Additional optimizations of such classes might entail specializing
+ * classes for leaf steps, subdividing by say, four, instead of two
+ * per iteration, and using an adaptive threshold instead of always
+ * subdividing down to single elements.
+ *
+ * <p><b>Searching.</b> A tree of CountedCompleters can search for a
+ * value or property in different parts of a data structure, and
+ * report a result in an {@link
+ * java.util.concurrent.atomic.AtomicReference AtomicReference} as
+ * soon as one is found. The others can poll the result to avoid
+ * unnecessary work. (You could additionally {@linkplain #cancel
+ * cancel} other tasks, but it is usually simpler and more efficient
+ * to just let them notice that the result is set and if so skip
+ * further processing.)  Illustrating again with an array using full
+ * partitioning (again, in practice, leaf tasks will almost always
+ * process more than one element):
+ *
+ * <pre> {@code
+ * class Searcher<E> extends CountedCompleter<E> {
+ *   final E[] array; final AtomicReference<E> result; final int lo, hi;
+ *   Searcher(CountedCompleter<?> p, E[] array, AtomicReference<E> result, int lo, int hi) {
+ *     super(p);
+ *     this.array = array; this.result = result; this.lo = lo; this.hi = hi;
+ *   }
+ *   public E getRawResult() { return result.get(); }
+ *   public void compute() { // similar to ForEach version 3
+ *     int l = lo, h = hi;
+ *     while (result.get() == null && h >= l) {
+ *       if (h - l >= 2) {
+ *         int mid = (l + h) >>> 1;
+ *         addToPendingCount(1);
+ *         new Searcher(this, array, result, mid, h).fork();
+ *         h = mid;
+ *       }
+ *       else {
+ *         E x = array[l];
+ *         if (matches(x) && result.compareAndSet(null, x))
+ *           quietlyCompleteRoot(); // root task is now joinable
+ *         break;
+ *       }
+ *     }
+ *     tryComplete(); // normally complete whether or not found
+ *   }
+ *   boolean matches(E e) { ... } // return true if found
+ *
+ *   public static <E> E search(E[] array) {
+ *       return new Searcher<E>(null, array, new AtomicReference<E>(), 0, array.length).invoke();
+ *   }
+ * }}</pre>
+ *
+ * In this example, as well as others in which tasks have no other
+ * effects except to {@code compareAndSet} a common result, the
+ * trailing unconditional invocation of {@code tryComplete} could be
+ * made conditional ({@code if (result.get() == null) tryComplete();})
+ * because no further bookkeeping is required to manage completions
+ * once the root task completes.
+ *
+ * <p><b>Recording subtasks.</b> CountedCompleter tasks that combine
+ * results of multiple subtasks usually need to access these results
+ * in method {@link #onCompletion(CountedCompleter)}. As illustrated in the following
+ * class (that performs a simplified form of map-reduce where mappings
+ * and reductions are all of type {@code E}), one way to do this in
+ * divide and conquer designs is to have each subtask record its
+ * sibling, so that it can be accessed in method {@code onCompletion}.
+ * This technique applies to reductions in which the order of
+ * combining left and right results does not matter; ordered
+ * reductions require explicit left/right designations.  Variants of
+ * other streamlinings seen in the above examples may also apply.
+ *
+ * <pre> {@code
+ * class MyMapper<E> { E apply(E v) {  ...  } }
+ * class MyReducer<E> { E apply(E x, E y) {  ...  } }
+ * class MapReducer<E> extends CountedCompleter<E> {
+ *   final E[] array; final MyMapper<E> mapper;
+ *   final MyReducer<E> reducer; final int lo, hi;
+ *   MapReducer<E> sibling;
+ *   E result;
+ *   MapReducer(CountedCompleter<?> p, E[] array, MyMapper<E> mapper,
+ *              MyReducer<E> reducer, int lo, int hi) {
+ *     super(p);
+ *     this.array = array; this.mapper = mapper;
+ *     this.reducer = reducer; this.lo = lo; this.hi = hi;
+ *   }
+ *   public void compute() {
+ *     if (hi - lo >= 2) {
+ *       int mid = (lo + hi) >>> 1;
+ *       MapReducer<E> left = new MapReducer(this, array, mapper, reducer, lo, mid);
+ *       MapReducer<E> right = new MapReducer(this, array, mapper, reducer, mid, hi);
+ *       left.sibling = right;
+ *       right.sibling = left;
+ *       setPendingCount(1); // only right is pending
+ *       right.fork();
+ *       left.compute();     // directly execute left
+ *     }
+ *     else {
+ *       if (hi > lo)
+ *           result = mapper.apply(array[lo]);
+ *       tryComplete();
+ *     }
+ *   }
+ *   public void onCompletion(CountedCompleter<?> caller) {
+ *     if (caller != this) {
+ *       MapReducer<E> child = (MapReducer<E>)caller;
+ *       MapReducer<E> sib = child.sibling;
+ *       if (sib == null || sib.result == null)
+ *         result = child.result;
+ *       else
+ *         result = reducer.apply(child.result, sib.result);
+ *     }
+ *   }
+ *   public E getRawResult() { return result; }
+ *
+ *   public static <E> E mapReduce(E[] array, MyMapper<E> mapper, MyReducer<E> reducer) {
+ *     return new MapReducer<E>(null, array, mapper, reducer,
+ *                              0, array.length).invoke();
+ *   }
+ * }}</pre>
+ *
+ * Here, method {@code onCompletion} takes a form common to many
+ * completion designs that combine results. This callback-style method
+ * is triggered once per task, in either of the two different contexts
+ * in which the pending count is, or becomes, zero: (1) by a task
+ * itself, if its pending count is zero upon invocation of {@code
+ * tryComplete}, or (2) by any of its subtasks when they complete and
+ * decrement the pending count to zero. The {@code caller} argument
+ * distinguishes cases.  Most often, when the caller is {@code this},
+ * no action is necessary. Otherwise the caller argument can be used
+ * (usually via a cast) to supply a value (and/or links to other
+ * values) to be combined.  Assuming proper use of pending counts, the
+ * actions inside {@code onCompletion} occur (once) upon completion of
+ * a task and its subtasks. No additional synchronization is required
+ * within this method to ensure thread safety of accesses to fields of
+ * this task or other completed tasks.
+ *
+ * <p><b>Completion Traversals</b>. If using {@code onCompletion} to
+ * process completions is inapplicable or inconvenient, you can use
+ * methods {@link #firstComplete} and {@link #nextComplete} to create
+ * custom traversals.  For example, to define a MapReducer that only
+ * splits out right-hand tasks in the form of the third ForEach
+ * example, the completions must cooperatively reduce along
+ * unexhausted subtask links, which can be done as follows:
+ *
+ * <pre> {@code
+ * class MapReducer<E> extends CountedCompleter<E> { // version 2
+ *   final E[] array; final MyMapper<E> mapper;
+ *   final MyReducer<E> reducer; final int lo, hi;
+ *   MapReducer<E> forks, next; // record subtask forks in list
+ *   E result;
+ *   MapReducer(CountedCompleter<?> p, E[] array, MyMapper<E> mapper,
+ *              MyReducer<E> reducer, int lo, int hi, MapReducer<E> next) {
+ *     super(p);
+ *     this.array = array; this.mapper = mapper;
+ *     this.reducer = reducer; this.lo = lo; this.hi = hi;
+ *     this.next = next;
+ *   }
+ *   public void compute() {
+ *     int l = lo, h = hi;
+ *     while (h - l >= 2) {
+ *       int mid = (l + h) >>> 1;
+ *       addToPendingCount(1);
+ *       (forks = new MapReducer(this, array, mapper, reducer, mid, h, forks)).fork();
+ *       h = mid;
+ *     }
+ *     if (h > l)
+ *       result = mapper.apply(array[l]);
+ *     // process completions by reducing along and advancing subtask links
+ *     for (CountedCompleter<?> c = firstComplete(); c != null; c = c.nextComplete()) {
+ *       for (MapReducer t = (MapReducer)c, s = t.forks; s != null; s = t.forks = s.next)
+ *         t.result = reducer.apply(t.result, s.result);
+ *     }
+ *   }
+ *   public E getRawResult() { return result; }
+ *
+ *   public static <E> E mapReduce(E[] array, MyMapper<E> mapper, MyReducer<E> reducer) {
+ *     return new MapReducer<E>(null, array, mapper, reducer,
+ *                              0, array.length, null).invoke();
+ *   }
+ * }}</pre>
+ *
+ * <p><b>Triggers.</b> Some CountedCompleters are themselves never
+ * forked, but instead serve as bits of plumbing in other designs;
+ * including those in which the completion of one or more async tasks
+ * triggers another async task. For example:
+ *
+ * <pre> {@code
+ * class HeaderBuilder extends CountedCompleter<...> { ... }
+ * class BodyBuilder extends CountedCompleter<...> { ... }
+ * class PacketSender extends CountedCompleter<...> {
+ *   PacketSender(...) { super(null, 1); ... } // trigger on second completion
+ *   public void compute() { } // never called
+ *   public void onCompletion(CountedCompleter<?> caller) { sendPacket(); }
+ * }
+ * // sample use:
+ * PacketSender p = new PacketSender();
+ * new HeaderBuilder(p, ...).fork();
+ * new BodyBuilder(p, ...).fork();}</pre>
+ *
+ * @since 1.8
+ * @author Doug Lea
+ */
+public abstract class CountedCompleter<T> extends ForkJoinTask<T> {
+    private static final long serialVersionUID = 5232453752276485070L;
+
+    /** This task's completer, or null if none */
+    final CountedCompleter<?> completer;
+    /** The number of pending tasks until completion */
+    volatile int pending;
+
+    /**
+     * Creates a new CountedCompleter with the given completer
+     * and initial pending count.
+     *
+     * @param completer this task's completer, or {@code null} if none
+     * @param initialPendingCount the initial pending count
+     */
+    protected CountedCompleter(CountedCompleter<?> completer,
+                               int initialPendingCount) {
+        this.completer = completer;
+        this.pending = initialPendingCount;
+    }
+
+    /**
+     * Creates a new CountedCompleter with the given completer
+     * and an initial pending count of zero.
+     *
+     * @param completer this task's completer, or {@code null} if none
+     */
+    protected CountedCompleter(CountedCompleter<?> completer) {
+        this.completer = completer;
+    }
+
+    /**
+     * Creates a new CountedCompleter with no completer
+     * and an initial pending count of zero.
+     */
+    protected CountedCompleter() {
+        this.completer = null;
+    }
+
+    /**
+     * The main computation performed by this task.
+     */
+    public abstract void compute();
+
+    /**
+     * Performs an action when method {@link #tryComplete} is invoked
+     * and the pending count is zero, or when the unconditional
+     * method {@link #complete} is invoked.  By default, this method
+     * does nothing. You can distinguish cases by checking the
+     * identity of the given caller argument. If not equal to {@code
+     * this}, then it is typically a subtask that may contain results
+     * (and/or links to other results) to combine.
+     *
+     * @param caller the task invoking this method (which may
+     * be this task itself)
+     */
+    public void onCompletion(CountedCompleter<?> caller) {
+    }
+
+    /**
+     * Performs an action when method {@link
+     * #completeExceptionally(Throwable)} is invoked or method {@link
+     * #compute} throws an exception, and this task has not already
+     * otherwise completed normally. On entry to this method, this task
+     * {@link ForkJoinTask#isCompletedAbnormally}.  The return value
+     * of this method controls further propagation: If {@code true}
+     * and this task has a completer that has not completed, then that
+     * completer is also completed exceptionally, with the same
+     * exception as this completer.  The default implementation of
+     * this method does nothing except return {@code true}.
+     *
+     * @param ex the exception
+     * @param caller the task invoking this method (which may
+     * be this task itself)
+     * @return {@code true} if this exception should be propagated to this
+     * task's completer, if one exists
+     */
+    public boolean onExceptionalCompletion(Throwable ex, CountedCompleter<?> caller) {
+        return true;
+    }
+
+    /**
+     * Returns the completer established in this task's constructor,
+     * or {@code null} if none.
+     *
+     * @return the completer
+     */
+    public final CountedCompleter<?> getCompleter() {
+        return completer;
+    }
+
+    /**
+     * Returns the current pending count.
+     *
+     * @return the current pending count
+     */
+    public final int getPendingCount() {
+        return pending;
+    }
+
+    /**
+     * Sets the pending count to the given value.
+     *
+     * @param count the count
+     */
+    public final void setPendingCount(int count) {
+        pending = count;
+    }
+
+    /**
+     * Adds (atomically) the given value to the pending count.
+     *
+     * @param delta the value to add
+     */
+    public final void addToPendingCount(int delta) {
+        PENDING.getAndAdd(this, delta);
+    }
+
+    /**
+     * Sets (atomically) the pending count to the given count only if
+     * it currently holds the given expected value.
+     *
+     * @param expected the expected value
+     * @param count the new value
+     * @return {@code true} if successful
+     */
+    public final boolean compareAndSetPendingCount(int expected, int count) {
+        return PENDING.compareAndSet(this, expected, count);
+    }
+
+    /**
+     * If the pending count is nonzero, (atomically) decrements it.
+     *
+     * @return the initial (undecremented) pending count holding on entry
+     * to this method
+     */
+    public final int decrementPendingCountUnlessZero() {
+        int c;
+        do {} while ((c = pending) != 0 &&
+                     !PENDING.weakCompareAndSet(this, c, c - 1));
+        return c;
+    }
+
+    /**
+     * Returns the root of the current computation; i.e., this
+     * task if it has no completer, else its completer's root.
+     *
+     * @return the root of the current computation
+     */
+    public final CountedCompleter<?> getRoot() {
+        CountedCompleter<?> a = this, p;
+        while ((p = a.completer) != null)
+            a = p;
+        return a;
+    }
+
+    /**
+     * If the pending count is nonzero, decrements the count;
+     * otherwise invokes {@link #onCompletion(CountedCompleter)}
+     * and then similarly tries to complete this task's completer,
+     * if one exists, else marks this task as complete.
+     */
+    public final void tryComplete() {
+        CountedCompleter<?> a = this, s = a;
+        for (int c;;) {
+            if ((c = a.pending) == 0) {
+                a.onCompletion(s);
+                if ((a = (s = a).completer) == null) {
+                    s.quietlyComplete();
+                    return;
+                }
+            }
+            else if (PENDING.weakCompareAndSet(a, c, c - 1))
+                return;
+        }
+    }
+
+    /**
+     * Equivalent to {@link #tryComplete} but does not invoke {@link
+     * #onCompletion(CountedCompleter)} along the completion path:
+     * If the pending count is nonzero, decrements the count;
+     * otherwise, similarly tries to complete this task's completer, if
+     * one exists, else marks this task as complete. This method may be
+     * useful in cases where {@code onCompletion} should not, or need
+     * not, be invoked for each completer in a computation.
+     */
+    public final void propagateCompletion() {
+        CountedCompleter<?> a = this, s;
+        for (int c;;) {
+            if ((c = a.pending) == 0) {
+                if ((a = (s = a).completer) == null) {
+                    s.quietlyComplete();
+                    return;
+                }
+            }
+            else if (PENDING.weakCompareAndSet(a, c, c - 1))
+                return;
+        }
+    }
+
+    /**
+     * Regardless of pending count, invokes
+     * {@link #onCompletion(CountedCompleter)}, marks this task as
+     * complete and further triggers {@link #tryComplete} on this
+     * task's completer, if one exists.  The given rawResult is
+     * used as an argument to {@link #setRawResult} before invoking
+     * {@link #onCompletion(CountedCompleter)} or marking this task
+     * as complete; its value is meaningful only for classes
+     * overriding {@code setRawResult}.  This method does not modify
+     * the pending count.
+     *
+     * <p>This method may be useful when forcing completion as soon as
+     * any one (versus all) of several subtask results are obtained.
+     * However, in the common (and recommended) case in which {@code
+     * setRawResult} is not overridden, this effect can be obtained
+     * more simply using {@link #quietlyCompleteRoot()}.
+     *
+     * @param rawResult the raw result
+     */
+    public void complete(T rawResult) {
+        CountedCompleter<?> p;
+        setRawResult(rawResult);
+        onCompletion(this);
+        quietlyComplete();
+        if ((p = completer) != null)
+            p.tryComplete();
+    }
+
+    /**
+     * If this task's pending count is zero, returns this task;
+     * otherwise decrements its pending count and returns {@code null}.
+     * This method is designed to be used with {@link #nextComplete} in
+     * completion traversal loops.
+     *
+     * @return this task, if pending count was zero, else {@code null}
+     */
+    public final CountedCompleter<?> firstComplete() {
+        for (int c;;) {
+            if ((c = pending) == 0)
+                return this;
+            else if (PENDING.weakCompareAndSet(this, c, c - 1))
+                return null;
+        }
+    }
+
+    /**
+     * If this task does not have a completer, invokes {@link
+     * ForkJoinTask#quietlyComplete} and returns {@code null}.  Or, if
+     * the completer's pending count is non-zero, decrements that
+     * pending count and returns {@code null}.  Otherwise, returns the
+     * completer.  This method can be used as part of a completion
+     * traversal loop for homogeneous task hierarchies:
+     *
+     * <pre> {@code
+     * for (CountedCompleter<?> c = firstComplete();
+     *      c != null;
+     *      c = c.nextComplete()) {
+     *   // ... process c ...
+     * }}</pre>
+     *
+     * @return the completer, or {@code null} if none
+     */
+    public final CountedCompleter<?> nextComplete() {
+        CountedCompleter<?> p;
+        if ((p = completer) != null)
+            return p.firstComplete();
+        else {
+            quietlyComplete();
+            return null;
+        }
+    }
+
+    /**
+     * Equivalent to {@code getRoot().quietlyComplete()}.
+     */
+    public final void quietlyCompleteRoot() {
+        for (CountedCompleter<?> a = this, p;;) {
+            if ((p = a.completer) == null) {
+                a.quietlyComplete();
+                return;
+            }
+            a = p;
+        }
+    }
+
+    /**
+     * If this task has not completed, attempts to process at most the
+     * given number of other unprocessed tasks for which this task is
+     * on the completion path, if any are known to exist.
+     *
+     * @param maxTasks the maximum number of tasks to process.  If
+     *                 less than or equal to zero, then no tasks are
+     *                 processed.
+     */
+    public final void helpComplete(int maxTasks) {
+        Thread t; ForkJoinWorkerThread wt;
+        if (maxTasks > 0 && status >= 0) {
+            if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread)
+                (wt = (ForkJoinWorkerThread)t).pool.
+                    helpComplete(wt.workQueue, this, maxTasks);
+            else
+                ForkJoinPool.common.externalHelpComplete(this, maxTasks);
+        }
+    }
+
+    /**
+     * Supports ForkJoinTask exception propagation.
+     */
+    void internalPropagateException(Throwable ex) {
+        CountedCompleter<?> a = this, s = a;
+        while (a.onExceptionalCompletion(ex, s) &&
+               (a = (s = a).completer) != null && a.status >= 0 &&
+               a.recordExceptionalCompletion(ex) == EXCEPTIONAL)
+            ;
+    }
+
+    /**
+     * Implements execution conventions for CountedCompleters.
+     */
+    protected final boolean exec() {
+        compute();
+        return false;
+    }
+
+    /**
+     * Returns the result of the computation.  By default,
+     * returns {@code null}, which is appropriate for {@code Void}
+     * actions, but in other cases should be overridden, almost
+     * always to return a field or function of a field that
+     * holds the result upon completion.
+     *
+     * @return the result of the computation
+     */
+    public T getRawResult() { return null; }
+
+    /**
+     * A method that result-bearing CountedCompleters may optionally
+     * use to help maintain result data.  By default, does nothing.
+     * Overrides are not recommended. However, if this method is
+     * overridden to update existing objects or fields, then it must
+     * in general be defined to be thread-safe.
+     */
+    protected void setRawResult(T t) { }
+
+    // VarHandle mechanics
+    private static final VarHandle PENDING;
+    static {
+        try {
+            MethodHandles.Lookup l = MethodHandles.lookup();
+            PENDING = l.findVarHandle(CountedCompleter.class, "pending", int.class);
+
+        } catch (ReflectiveOperationException e) {
+            throw new Error(e);
+        }
+    }
+}

src/java.base/share/classes/java/util/concurrent/CyclicBarrier.java

@@ -0,0 +1,492 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent;
+
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.ReentrantLock;
+
+/**
+ * A synchronization aid that allows a set of threads to all wait for
+ * each other to reach a common barrier point.  CyclicBarriers are
+ * useful in programs involving a fixed sized party of threads that
+ * must occasionally wait for each other. The barrier is called
+ * <em>cyclic</em> because it can be re-used after the waiting threads
+ * are released.
+ *
+ * <p>A {@code CyclicBarrier} supports an optional {@link Runnable} command
+ * that is run once per barrier point, after the last thread in the party
+ * arrives, but before any threads are released.
+ * This <em>barrier action</em> is useful
+ * for updating shared-state before any of the parties continue.
+ *
+ * <p><b>Sample usage:</b> Here is an example of using a barrier in a
+ * parallel decomposition design:
+ *
+ * <pre> {@code
+ * class Solver {
+ *   final int N;
+ *   final float[][] data;
+ *   final CyclicBarrier barrier;
+ *
+ *   class Worker implements Runnable {
+ *     int myRow;
+ *     Worker(int row) { myRow = row; }
+ *     public void run() {
+ *       while (!done()) {
+ *         processRow(myRow);
+ *
+ *         try {
+ *           barrier.await();
+ *         } catch (InterruptedException ex) {
+ *           return;
+ *         } catch (BrokenBarrierException ex) {
+ *           return;
+ *         }
+ *       }
+ *     }
+ *   }
+ *
+ *   public Solver(float[][] matrix) {
+ *     data = matrix;
+ *     N = matrix.length;
+ *     Runnable barrierAction = () -> mergeRows(...);
+ *     barrier = new CyclicBarrier(N, barrierAction);
+ *
+ *     List<Thread> threads = new ArrayList<>(N);
+ *     for (int i = 0; i < N; i++) {
+ *       Thread thread = new Thread(new Worker(i));
+ *       threads.add(thread);
+ *       thread.start();
+ *     }
+ *
+ *     // wait until done
+ *     for (Thread thread : threads)
+ *       thread.join();
+ *   }
+ * }}</pre>
+ *
+ * Here, each worker thread processes a row of the matrix then waits at the
+ * barrier until all rows have been processed. When all rows are processed
+ * the supplied {@link Runnable} barrier action is executed and merges the
+ * rows. If the merger
+ * determines that a solution has been found then {@code done()} will return
+ * {@code true} and each worker will terminate.
+ *
+ * <p>If the barrier action does not rely on the parties being suspended when
+ * it is executed, then any of the threads in the party could execute that
+ * action when it is released. To facilitate this, each invocation of
+ * {@link #await} returns the arrival index of that thread at the barrier.
+ * You can then choose which thread should execute the barrier action, for
+ * example:
+ * <pre> {@code
+ * if (barrier.await() == 0) {
+ *   // log the completion of this iteration
+ * }}</pre>
+ *
+ * <p>The {@code CyclicBarrier} uses an all-or-none breakage model
+ * for failed synchronization attempts: If a thread leaves a barrier
+ * point prematurely because of interruption, failure, or timeout, all
+ * other threads waiting at that barrier point will also leave
+ * abnormally via {@link BrokenBarrierException} (or
+ * {@link InterruptedException} if they too were interrupted at about
+ * the same time).
+ *
+ * <p>Memory consistency effects: Actions in a thread prior to calling
+ * {@code await()}
+ * <a href="package-summary.html#MemoryVisibility"><i>happen-before</i></a>
+ * actions that are part of the barrier action, which in turn
+ * <i>happen-before</i> actions following a successful return from the
+ * corresponding {@code await()} in other threads.
+ *
+ * @see CountDownLatch
+ *
+ * @author Doug Lea
+ * @since 1.5
+ */
+public class CyclicBarrier {
+    /**
+     * Each use of the barrier is represented as a generation instance.
+     * The generation changes whenever the barrier is tripped, or
+     * is reset. There can be many generations associated with threads
+     * using the barrier - due to the non-deterministic way the lock
+     * may be allocated to waiting threads - but only one of these
+     * can be active at a time (the one to which {@code count} applies)
+     * and all the rest are either broken or tripped.
+     * There need not be an active generation if there has been a break
+     * but no subsequent reset.
+     */
+    private static class Generation {
+        Generation() {}                 // prevent access constructor creation
+        boolean broken;                 // initially false
+    }
+
+    /** The lock for guarding barrier entry */
+    private final ReentrantLock lock = new ReentrantLock();
+    /** Condition to wait on until tripped */
+    private final Condition trip = lock.newCondition();
+    /** The number of parties */
+    private final int parties;
+    /** The command to run when tripped */
+    private final Runnable barrierCommand;
+    /** The current generation */
+    private Generation generation = new Generation();
+
+    /**
+     * Number of parties still waiting. Counts down from parties to 0
+     * on each generation.  It is reset to parties on each new
+     * generation or when broken.
+     */
+    private int count;
+
+    /**
+     * Updates state on barrier trip and wakes up everyone.
+     * Called only while holding lock.
+     */
+    private void nextGeneration() {
+        // signal completion of last generation
+        trip.signalAll();
+        // set up next generation
+        count = parties;
+        generation = new Generation();
+    }
+
+    /**
+     * Sets current barrier generation as broken and wakes up everyone.
+     * Called only while holding lock.
+     */
+    private void breakBarrier() {
+        generation.broken = true;
+        count = parties;
+        trip.signalAll();
+    }
+
+    /**
+     * Main barrier code, covering the various policies.
+     */
+    private int dowait(boolean timed, long nanos)
+        throws InterruptedException, BrokenBarrierException,
+               TimeoutException {
+        final ReentrantLock lock = this.lock;
+        lock.lock();
+        try {
+            final Generation g = generation;
+
+            if (g.broken)
+                throw new BrokenBarrierException();
+
+            if (Thread.interrupted()) {
+                breakBarrier();
+                throw new InterruptedException();
+            }
+
+            int index = --count;
+            if (index == 0) {  // tripped
+                boolean ranAction = false;
+                try {
+                    final Runnable command = barrierCommand;
+                    if (command != null)
+                        command.run();
+                    ranAction = true;
+                    nextGeneration();
+                    return 0;
+                } finally {
+                    if (!ranAction)
+                        breakBarrier();
+                }
+            }
+
+            // loop until tripped, broken, interrupted, or timed out
+            for (;;) {
+                try {
+                    if (!timed)
+                        trip.await();
+                    else if (nanos > 0L)
+                        nanos = trip.awaitNanos(nanos);
+                } catch (InterruptedException ie) {
+                    if (g == generation && ! g.broken) {
+                        breakBarrier();
+                        throw ie;
+                    } else {
+                        // We're about to finish waiting even if we had not
+                        // been interrupted, so this interrupt is deemed to
+                        // "belong" to subsequent execution.
+                        Thread.currentThread().interrupt();
+                    }
+                }
+
+                if (g.broken)
+                    throw new BrokenBarrierException();
+
+                if (g != generation)
+                    return index;
+
+                if (timed && nanos <= 0L) {
+                    breakBarrier();
+                    throw new TimeoutException();
+                }
+            }
+        } finally {
+            lock.unlock();
+        }
+    }
+
+    /**
+     * Creates a new {@code CyclicBarrier} that will trip when the
+     * given number of parties (threads) are waiting upon it, and which
+     * will execute the given barrier action when the barrier is tripped,
+     * performed by the last thread entering the barrier.
+     *
+     * @param parties the number of threads that must invoke {@link #await}
+     *        before the barrier is tripped
+     * @param barrierAction the command to execute when the barrier is
+     *        tripped, or {@code null} if there is no action
+     * @throws IllegalArgumentException if {@code parties} is less than 1
+     */
+    public CyclicBarrier(int parties, Runnable barrierAction) {
+        if (parties <= 0) throw new IllegalArgumentException();
+        this.parties = parties;
+        this.count = parties;
+        this.barrierCommand = barrierAction;
+    }
+
+    /**
+     * Creates a new {@code CyclicBarrier} that will trip when the
+     * given number of parties (threads) are waiting upon it, and
+     * does not perform a predefined action when the barrier is tripped.
+     *
+     * @param parties the number of threads that must invoke {@link #await}
+     *        before the barrier is tripped
+     * @throws IllegalArgumentException if {@code parties} is less than 1
+     */
+    public CyclicBarrier(int parties) {
+        this(parties, null);
+    }
+
+    /**
+     * Returns the number of parties required to trip this barrier.
+     *
+     * @return the number of parties required to trip this barrier
+     */
+    public int getParties() {
+        return parties;
+    }
+
+    /**
+     * Waits until all {@linkplain #getParties parties} have invoked
+     * {@code await} on this barrier.
+     *
+     * <p>If the current thread is not the last to arrive then it is
+     * disabled for thread scheduling purposes and lies dormant until
+     * one of the following things happens:
+     * <ul>
+     * <li>The last thread arrives; or
+     * <li>Some other thread {@linkplain Thread#interrupt interrupts}
+     * the current thread; or
+     * <li>Some other thread {@linkplain Thread#interrupt interrupts}
+     * one of the other waiting threads; or
+     * <li>Some other thread times out while waiting for barrier; or
+     * <li>Some other thread invokes {@link #reset} on this barrier.
+     * </ul>
+     *
+     * <p>If the current thread:
+     * <ul>
+     * <li>has its interrupted status set on entry to this method; or
+     * <li>is {@linkplain Thread#interrupt interrupted} while waiting
+     * </ul>
+     * then {@link InterruptedException} is thrown and the current thread's
+     * interrupted status is cleared.
+     *
+     * <p>If the barrier is {@link #reset} while any thread is waiting,
+     * or if the barrier {@linkplain #isBroken is broken} when
+     * {@code await} is invoked, or while any thread is waiting, then
+     * {@link BrokenBarrierException} is thrown.
+     *
+     * <p>If any thread is {@linkplain Thread#interrupt interrupted} while waiting,
+     * then all other waiting threads will throw
+     * {@link BrokenBarrierException} and the barrier is placed in the broken
+     * state.
+     *
+     * <p>If the current thread is the last thread to arrive, and a
+     * non-null barrier action was supplied in the constructor, then the
+     * current thread runs the action before allowing the other threads to
+     * continue.
+     * If an exception occurs during the barrier action then that exception
+     * will be propagated in the current thread and the barrier is placed in
+     * the broken state.
+     *
+     * @return the arrival index of the current thread, where index
+     *         {@code getParties() - 1} indicates the first
+     *         to arrive and zero indicates the last to arrive
+     * @throws InterruptedException if the current thread was interrupted
+     *         while waiting
+     * @throws BrokenBarrierException if <em>another</em> thread was
+     *         interrupted or timed out while the current thread was
+     *         waiting, or the barrier was reset, or the barrier was
+     *         broken when {@code await} was called, or the barrier
+     *         action (if present) failed due to an exception
+     */
+    public int await() throws InterruptedException, BrokenBarrierException {
+        try {
+            return dowait(false, 0L);
+        } catch (TimeoutException toe) {
+            throw new Error(toe); // cannot happen
+        }
+    }
+
+    /**
+     * Waits until all {@linkplain #getParties parties} have invoked
+     * {@code await} on this barrier, or the specified waiting time elapses.
+     *
+     * <p>If the current thread is not the last to arrive then it is
+     * disabled for thread scheduling purposes and lies dormant until
+     * one of the following things happens:
+     * <ul>
+     * <li>The last thread arrives; or
+     * <li>The specified timeout elapses; or
+     * <li>Some other thread {@linkplain Thread#interrupt interrupts}
+     * the current thread; or
+     * <li>Some other thread {@linkplain Thread#interrupt interrupts}
+     * one of the other waiting threads; or
+     * <li>Some other thread times out while waiting for barrier; or
+     * <li>Some other thread invokes {@link #reset} on this barrier.
+     * </ul>
+     *
+     * <p>If the current thread:
+     * <ul>
+     * <li>has its interrupted status set on entry to this method; or
+     * <li>is {@linkplain Thread#interrupt interrupted} while waiting
+     * </ul>
+     * then {@link InterruptedException} is thrown and the current thread's
+     * interrupted status is cleared.
+     *
+     * <p>If the specified waiting time elapses then {@link TimeoutException}
+     * is thrown. If the time is less than or equal to zero, the
+     * method will not wait at all.
+     *
+     * <p>If the barrier is {@link #reset} while any thread is waiting,
+     * or if the barrier {@linkplain #isBroken is broken} when
+     * {@code await} is invoked, or while any thread is waiting, then
+     * {@link BrokenBarrierException} is thrown.
+     *
+     * <p>If any thread is {@linkplain Thread#interrupt interrupted} while
+     * waiting, then all other waiting threads will throw {@link
+     * BrokenBarrierException} and the barrier is placed in the broken
+     * state.
+     *
+     * <p>If the current thread is the last thread to arrive, and a
+     * non-null barrier action was supplied in the constructor, then the
+     * current thread runs the action before allowing the other threads to
+     * continue.
+     * If an exception occurs during the barrier action then that exception
+     * will be propagated in the current thread and the barrier is placed in
+     * the broken state.
+     *
+     * @param timeout the time to wait for the barrier
+     * @param unit the time unit of the timeout parameter
+     * @return the arrival index of the current thread, where index
+     *         {@code getParties() - 1} indicates the first
+     *         to arrive and zero indicates the last to arrive
+     * @throws InterruptedException if the current thread was interrupted
+     *         while waiting
+     * @throws TimeoutException if the specified timeout elapses.
+     *         In this case the barrier will be broken.
+     * @throws BrokenBarrierException if <em>another</em> thread was
+     *         interrupted or timed out while the current thread was
+     *         waiting, or the barrier was reset, or the barrier was broken
+     *         when {@code await} was called, or the barrier action (if
+     *         present) failed due to an exception
+     */
+    public int await(long timeout, TimeUnit unit)
+        throws InterruptedException,
+               BrokenBarrierException,
+               TimeoutException {
+        return dowait(true, unit.toNanos(timeout));
+    }
+
+    /**
+     * Queries if this barrier is in a broken state.
+     *
+     * @return {@code true} if one or more parties broke out of this
+     *         barrier due to interruption or timeout since
+     *         construction or the last reset, or a barrier action
+     *         failed due to an exception; {@code false} otherwise.
+     */
+    public boolean isBroken() {
+        final ReentrantLock lock = this.lock;
+        lock.lock();
+        try {
+            return generation.broken;
+        } finally {
+            lock.unlock();
+        }
+    }
+
+    /**
+     * Resets the barrier to its initial state.  If any parties are
+     * currently waiting at the barrier, they will return with a
+     * {@link BrokenBarrierException}. Note that resets <em>after</em>
+     * a breakage has occurred for other reasons can be complicated to
+     * carry out; threads need to re-synchronize in some other way,
+     * and choose one to perform the reset.  It may be preferable to
+     * instead create a new barrier for subsequent use.
+     */
+    public void reset() {
+        final ReentrantLock lock = this.lock;
+        lock.lock();
+        try {
+            breakBarrier();   // break the current generation
+            nextGeneration(); // start a new generation
+        } finally {
+            lock.unlock();
+        }
+    }
+
+    /**
+     * Returns the number of parties currently waiting at the barrier.
+     * This method is primarily useful for debugging and assertions.
+     *
+     * @return the number of parties currently blocked in {@link #await}
+     */
+    public int getNumberWaiting() {
+        final ReentrantLock lock = this.lock;
+        lock.lock();
+        try {
+            return parties - count;
+        } finally {
+            lock.unlock();
+        }
+    }
+}

src/java.base/share/classes/java/util/concurrent/DelayQueue.java

@@ -0,0 +1,537 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent;
+
+import static java.util.concurrent.TimeUnit.NANOSECONDS;
+
+import java.util.AbstractQueue;
+import java.util.Collection;
+import java.util.Iterator;
+import java.util.NoSuchElementException;
+import java.util.Objects;
+import java.util.PriorityQueue;
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.ReentrantLock;
+
+/**
+ * An unbounded {@linkplain BlockingQueue blocking queue} of
+ * {@code Delayed} elements, in which an element can only be taken
+ * when its delay has expired.  The <em>head</em> of the queue is that
+ * {@code Delayed} element whose delay expired furthest in the
+ * past.  If no delay has expired there is no head and {@code poll}
+ * will return {@code null}. Expiration occurs when an element's
+ * {@code getDelay(TimeUnit.NANOSECONDS)} method returns a value less
+ * than or equal to zero.  Even though unexpired elements cannot be
+ * removed using {@code take} or {@code poll}, they are otherwise
+ * treated as normal elements. For example, the {@code size} method
+ * returns the count of both expired and unexpired elements.
+ * This queue does not permit null elements.
+ *
+ * <p>This class and its iterator implement all of the <em>optional</em>
+ * methods of the {@link Collection} and {@link Iterator} interfaces.
+ * The Iterator provided in method {@link #iterator()} is <em>not</em>
+ * guaranteed to traverse the elements of the DelayQueue in any
+ * particular order.
+ *
+ * <p>This class is a member of the
+ * <a href="{@docRoot}/java/util/package-summary.html#CollectionsFramework">
+ * Java Collections Framework</a>.
+ *
+ * @since 1.5
+ * @author Doug Lea
+ * @param <E> the type of elements held in this queue
+ */
+public class DelayQueue<E extends Delayed> extends AbstractQueue<E>
+    implements BlockingQueue<E> {
+
+    private final transient ReentrantLock lock = new ReentrantLock();
+    private final PriorityQueue<E> q = new PriorityQueue<E>();
+
+    /**
+     * Thread designated to wait for the element at the head of
+     * the queue.  This variant of the Leader-Follower pattern
+     * (http://www.cs.wustl.edu/~schmidt/POSA/POSA2/) serves to
+     * minimize unnecessary timed waiting.  When a thread becomes
+     * the leader, it waits only for the next delay to elapse, but
+     * other threads await indefinitely.  The leader thread must
+     * signal some other thread before returning from take() or
+     * poll(...), unless some other thread becomes leader in the
+     * interim.  Whenever the head of the queue is replaced with
+     * an element with an earlier expiration time, the leader
+     * field is invalidated by being reset to null, and some
+     * waiting thread, but not necessarily the current leader, is
+     * signalled.  So waiting threads must be prepared to acquire
+     * and lose leadership while waiting.
+     */
+    private Thread leader;
+
+    /**
+     * Condition signalled when a newer element becomes available
+     * at the head of the queue or a new thread may need to
+     * become leader.
+     */
+    private final Condition available = lock.newCondition();
+
+    /**
+     * Creates a new {@code DelayQueue} that is initially empty.
+     */
+    public DelayQueue() {}
+
+    /**
+     * Creates a {@code DelayQueue} initially containing the elements of the
+     * given collection of {@link Delayed} instances.
+     *
+     * @param c the collection of elements to initially contain
+     * @throws NullPointerException if the specified collection or any
+     *         of its elements are null
+     */
+    public DelayQueue(Collection<? extends E> c) {
+        this.addAll(c);
+    }
+
+    /**
+     * Inserts the specified element into this delay queue.
+     *
+     * @param e the element to add
+     * @return {@code true} (as specified by {@link Collection#add})
+     * @throws NullPointerException if the specified element is null
+     */
+    public boolean add(E e) {
+        return offer(e);
+    }
+
+    /**
+     * Inserts the specified element into this delay queue.
+     *
+     * @param e the element to add
+     * @return {@code true}
+     * @throws NullPointerException if the specified element is null
+     */
+    public boolean offer(E e) {
+        final ReentrantLock lock = this.lock;
+        lock.lock();
+        try {
+            q.offer(e);
+            if (q.peek() == e) {
+                leader = null;
+                available.signal();
+            }
+            return true;
+        } finally {
+            lock.unlock();
+        }
+    }
+
+    /**
+     * Inserts the specified element into this delay queue. As the queue is
+     * unbounded this method will never block.
+     *
+     * @param e the element to add
+     * @throws NullPointerException {@inheritDoc}
+     */
+    public void put(E e) {
+        offer(e);
+    }
+
+    /**
+     * Inserts the specified element into this delay queue. As the queue is
+     * unbounded this method will never block.
+     *
+     * @param e the element to add
+     * @param timeout This parameter is ignored as the method never blocks
+     * @param unit This parameter is ignored as the method never blocks
+     * @return {@code true}
+     * @throws NullPointerException {@inheritDoc}
+     */
+    public boolean offer(E e, long timeout, TimeUnit unit) {
+        return offer(e);
+    }
+
+    /**
+     * Retrieves and removes the head of this queue, or returns {@code null}
+     * if this queue has no elements with an expired delay.
+     *
+     * @return the head of this queue, or {@code null} if this
+     *         queue has no elements with an expired delay
+     */
+    public E poll() {
+        final ReentrantLock lock = this.lock;
+        lock.lock();
+        try {
+            E first = q.peek();
+            return (first == null || first.getDelay(NANOSECONDS) > 0)
+                ? null
+                : q.poll();
+        } finally {
+            lock.unlock();
+        }
+    }
+
+    /**
+     * Retrieves and removes the head of this queue, waiting if necessary
+     * until an element with an expired delay is available on this queue.
+     *
+     * @return the head of this queue
+     * @throws InterruptedException {@inheritDoc}
+     */
+    public E take() throws InterruptedException {
+        final ReentrantLock lock = this.lock;
+        lock.lockInterruptibly();
+        try {
+            for (;;) {
+                E first = q.peek();
+                if (first == null)
+                    available.await();
+                else {
+                    long delay = first.getDelay(NANOSECONDS);
+                    if (delay <= 0L)
+                        return q.poll();
+                    first = null; // don't retain ref while waiting
+                    if (leader != null)
+                        available.await();
+                    else {
+                        Thread thisThread = Thread.currentThread();
+                        leader = thisThread;
+                        try {
+                            available.awaitNanos(delay);
+                        } finally {
+                            if (leader == thisThread)
+                                leader = null;
+                        }
+                    }
+                }
+            }
+        } finally {
+            if (leader == null && q.peek() != null)
+                available.signal();
+            lock.unlock();
+        }
+    }
+
+    /**
+     * Retrieves and removes the head of this queue, waiting if necessary
+     * until an element with an expired delay is available on this queue,
+     * or the specified wait time expires.
+     *
+     * @return the head of this queue, or {@code null} if the
+     *         specified waiting time elapses before an element with
+     *         an expired delay becomes available
+     * @throws InterruptedException {@inheritDoc}
+     */
+    public E poll(long timeout, TimeUnit unit) throws InterruptedException {
+        long nanos = unit.toNanos(timeout);
+        final ReentrantLock lock = this.lock;
+        lock.lockInterruptibly();
+        try {
+            for (;;) {
+                E first = q.peek();
+                if (first == null) {
+                    if (nanos <= 0L)
+                        return null;
+                    else
+                        nanos = available.awaitNanos(nanos);
+                } else {
+                    long delay = first.getDelay(NANOSECONDS);
+                    if (delay <= 0L)
+                        return q.poll();
+                    if (nanos <= 0L)
+                        return null;
+                    first = null; // don't retain ref while waiting
+                    if (nanos < delay || leader != null)
+                        nanos = available.awaitNanos(nanos);
+                    else {
+                        Thread thisThread = Thread.currentThread();
+                        leader = thisThread;
+                        try {
+                            long timeLeft = available.awaitNanos(delay);
+                            nanos -= delay - timeLeft;
+                        } finally {
+                            if (leader == thisThread)
+                                leader = null;
+                        }
+                    }
+                }
+            }
+        } finally {
+            if (leader == null && q.peek() != null)
+                available.signal();
+            lock.unlock();
+        }
+    }
+
+    /**
+     * Retrieves, but does not remove, the head of this queue, or
+     * returns {@code null} if this queue is empty.  Unlike
+     * {@code poll}, if no expired elements are available in the queue,
+     * this method returns the element that will expire next,
+     * if one exists.
+     *
+     * @return the head of this queue, or {@code null} if this
+     *         queue is empty
+     */
+    public E peek() {
+        final ReentrantLock lock = this.lock;
+        lock.lock();
+        try {
+            return q.peek();
+        } finally {
+            lock.unlock();
+        }
+    }
+
+    public int size() {
+        final ReentrantLock lock = this.lock;
+        lock.lock();
+        try {
+            return q.size();
+        } finally {
+            lock.unlock();
+        }
+    }
+
+    /**
+     * @throws UnsupportedOperationException {@inheritDoc}
+     * @throws ClassCastException            {@inheritDoc}
+     * @throws NullPointerException          {@inheritDoc}
+     * @throws IllegalArgumentException      {@inheritDoc}
+     */
+    public int drainTo(Collection<? super E> c) {
+        return drainTo(c, Integer.MAX_VALUE);
+    }
+
+    /**
+     * @throws UnsupportedOperationException {@inheritDoc}
+     * @throws ClassCastException            {@inheritDoc}
+     * @throws NullPointerException          {@inheritDoc}
+     * @throws IllegalArgumentException      {@inheritDoc}
+     */
+    public int drainTo(Collection<? super E> c, int maxElements) {
+        Objects.requireNonNull(c);
+        if (c == this)
+            throw new IllegalArgumentException();
+        if (maxElements <= 0)
+            return 0;
+        final ReentrantLock lock = this.lock;
+        lock.lock();
+        try {
+            int n = 0;
+            for (E first;
+                 n < maxElements
+                     && (first = q.peek()) != null
+                     && first.getDelay(NANOSECONDS) <= 0;) {
+                c.add(first);   // In this order, in case add() throws.
+                q.poll();
+                ++n;
+            }
+            return n;
+        } finally {
+            lock.unlock();
+        }
+    }
+
+    /**
+     * Atomically removes all of the elements from this delay queue.
+     * The queue will be empty after this call returns.
+     * Elements with an unexpired delay are not waited for; they are
+     * simply discarded from the queue.
+     */
+    public void clear() {
+        final ReentrantLock lock = this.lock;
+        lock.lock();
+        try {
+            q.clear();
+        } finally {
+            lock.unlock();
+        }
+    }
+
+    /**
+     * Always returns {@code Integer.MAX_VALUE} because
+     * a {@code DelayQueue} is not capacity constrained.
+     *
+     * @return {@code Integer.MAX_VALUE}
+     */
+    public int remainingCapacity() {
+        return Integer.MAX_VALUE;
+    }
+
+    /**
+     * Returns an array containing all of the elements in this queue.
+     * The returned array elements are in no particular order.
+     *
+     * <p>The returned array will be "safe" in that no references to it are
+     * maintained by this queue.  (In other words, this method must allocate
+     * a new array).  The caller is thus free to modify the returned array.
+     *
+     * <p>This method acts as bridge between array-based and collection-based
+     * APIs.
+     *
+     * @return an array containing all of the elements in this queue
+     */
+    public Object[] toArray() {
+        final ReentrantLock lock = this.lock;
+        lock.lock();
+        try {
+            return q.toArray();
+        } finally {
+            lock.unlock();
+        }
+    }
+
+    /**
+     * Returns an array containing all of the elements in this queue; the
+     * runtime type of the returned array is that of the specified array.
+     * The returned array elements are in no particular order.
+     * If the queue fits in the specified array, it is returned therein.
+     * Otherwise, a new array is allocated with the runtime type of the
+     * specified array and the size of this queue.
+     *
+     * <p>If this queue fits in the specified array with room to spare
+     * (i.e., the array has more elements than this queue), the element in
+     * the array immediately following the end of the queue is set to
+     * {@code null}.
+     *
+     * <p>Like the {@link #toArray()} method, this method acts as bridge between
+     * array-based and collection-based APIs.  Further, this method allows
+     * precise control over the runtime type of the output array, and may,
+     * under certain circumstances, be used to save allocation costs.
+     *
+     * <p>The following code can be used to dump a delay queue into a newly
+     * allocated array of {@code Delayed}:
+     *
+     * <pre> {@code Delayed[] a = q.toArray(new Delayed[0]);}</pre>
+     *
+     * Note that {@code toArray(new Object[0])} is identical in function to
+     * {@code toArray()}.
+     *
+     * @param a the array into which the elements of the queue are to
+     *          be stored, if it is big enough; otherwise, a new array of the
+     *          same runtime type is allocated for this purpose
+     * @return an array containing all of the elements in this queue
+     * @throws ArrayStoreException if the runtime type of the specified array
+     *         is not a supertype of the runtime type of every element in
+     *         this queue
+     * @throws NullPointerException if the specified array is null
+     */
+    public <T> T[] toArray(T[] a) {
+        final ReentrantLock lock = this.lock;
+        lock.lock();
+        try {
+            return q.toArray(a);
+        } finally {
+            lock.unlock();
+        }
+    }
+
+    /**
+     * Removes a single instance of the specified element from this
+     * queue, if it is present, whether or not it has expired.
+     */
+    public boolean remove(Object o) {
+        final ReentrantLock lock = this.lock;
+        lock.lock();
+        try {
+            return q.remove(o);
+        } finally {
+            lock.unlock();
+        }
+    }
+
+    /**
+     * Identity-based version for use in Itr.remove.
+     */
+    void removeEQ(Object o) {
+        final ReentrantLock lock = this.lock;
+        lock.lock();
+        try {
+            for (Iterator<E> it = q.iterator(); it.hasNext(); ) {
+                if (o == it.next()) {
+                    it.remove();
+                    break;
+                }
+            }
+        } finally {
+            lock.unlock();
+        }
+    }
+
+    /**
+     * Returns an iterator over all the elements (both expired and
+     * unexpired) in this queue. The iterator does not return the
+     * elements in any particular order.
+     *
+     * <p>The returned iterator is
+     * <a href="package-summary.html#Weakly"><i>weakly consistent</i></a>.
+     *
+     * @return an iterator over the elements in this queue
+     */
+    public Iterator<E> iterator() {
+        return new Itr(toArray());
+    }
+
+    /**
+     * Snapshot iterator that works off copy of underlying q array.
+     */
+    private class Itr implements Iterator<E> {
+        final Object[] array; // Array of all elements
+        int cursor;           // index of next element to return
+        int lastRet;          // index of last element, or -1 if no such
+
+        Itr(Object[] array) {
+            lastRet = -1;
+            this.array = array;
+        }
+
+        public boolean hasNext() {
+            return cursor < array.length;
+        }
+
+        @SuppressWarnings("unchecked")
+        public E next() {
+            if (cursor >= array.length)
+                throw new NoSuchElementException();
+            return (E)array[lastRet = cursor++];
+        }
+
+        public void remove() {
+            if (lastRet < 0)
+                throw new IllegalStateException();
+            removeEQ(array[lastRet]);
+            lastRet = -1;
+        }
+    }
+
+}

src/java.base/share/classes/java/util/concurrent/Delayed.java

@@ -0,0 +1,60 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent;
+
+/**
+ * A mix-in style interface for marking objects that should be
+ * acted upon after a given delay.
+ *
+ * <p>An implementation of this interface must define a
+ * {@code compareTo} method that provides an ordering consistent with
+ * its {@code getDelay} method.
+ *
+ * @since 1.5
+ * @author Doug Lea
+ */
+public interface Delayed extends Comparable<Delayed> {
+
+    /**
+     * Returns the remaining delay associated with this object, in the
+     * given time unit.
+     *
+     * @param unit the time unit
+     * @return the remaining delay; zero or negative values indicate
+     * that the delay has already elapsed
+     */
+    long getDelay(TimeUnit unit);
+}

src/java.base/share/classes/java/util/concurrent/Exchanger.java

@@ -0,0 +1,648 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea, Bill Scherer, and Michael Scott with
+ * assistance from members of JCP JSR-166 Expert Group and released to
+ * the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent;
+
+import java.lang.invoke.MethodHandles;
+import java.lang.invoke.VarHandle;
+import java.util.concurrent.locks.LockSupport;
+
+/**
+ * A synchronization point at which threads can pair and swap elements
+ * within pairs.  Each thread presents some object on entry to the
+ * {@link #exchange exchange} method, matches with a partner thread,
+ * and receives its partner's object on return.  An Exchanger may be
+ * viewed as a bidirectional form of a {@link SynchronousQueue}.
+ * Exchangers may be useful in applications such as genetic algorithms
+ * and pipeline designs.
+ *
+ * <p><b>Sample Usage:</b>
+ * Here are the highlights of a class that uses an {@code Exchanger}
+ * to swap buffers between threads so that the thread filling the
+ * buffer gets a freshly emptied one when it needs it, handing off the
+ * filled one to the thread emptying the buffer.
+ * <pre> {@code
+ * class FillAndEmpty {
+ *   Exchanger<DataBuffer> exchanger = new Exchanger<>();
+ *   DataBuffer initialEmptyBuffer = ... a made-up type
+ *   DataBuffer initialFullBuffer = ...
+ *
+ *   class FillingLoop implements Runnable {
+ *     public void run() {
+ *       DataBuffer currentBuffer = initialEmptyBuffer;
+ *       try {
+ *         while (currentBuffer != null) {
+ *           addToBuffer(currentBuffer);
+ *           if (currentBuffer.isFull())
+ *             currentBuffer = exchanger.exchange(currentBuffer);
+ *         }
+ *       } catch (InterruptedException ex) { ... handle ... }
+ *     }
+ *   }
+ *
+ *   class EmptyingLoop implements Runnable {
+ *     public void run() {
+ *       DataBuffer currentBuffer = initialFullBuffer;
+ *       try {
+ *         while (currentBuffer != null) {
+ *           takeFromBuffer(currentBuffer);
+ *           if (currentBuffer.isEmpty())
+ *             currentBuffer = exchanger.exchange(currentBuffer);
+ *         }
+ *       } catch (InterruptedException ex) { ... handle ...}
+ *     }
+ *   }
+ *
+ *   void start() {
+ *     new Thread(new FillingLoop()).start();
+ *     new Thread(new EmptyingLoop()).start();
+ *   }
+ * }}</pre>
+ *
+ * <p>Memory consistency effects: For each pair of threads that
+ * successfully exchange objects via an {@code Exchanger}, actions
+ * prior to the {@code exchange()} in each thread
+ * <a href="package-summary.html#MemoryVisibility"><i>happen-before</i></a>
+ * those subsequent to a return from the corresponding {@code exchange()}
+ * in the other thread.
+ *
+ * @since 1.5
+ * @author Doug Lea and Bill Scherer and Michael Scott
+ * @param <V> The type of objects that may be exchanged
+ */
+public class Exchanger<V> {
+
+    /*
+     * Overview: The core algorithm is, for an exchange "slot",
+     * and a participant (caller) with an item:
+     *
+     * for (;;) {
+     *   if (slot is empty) {                       // offer
+     *     place item in a Node;
+     *     if (can CAS slot from empty to node) {
+     *       wait for release;
+     *       return matching item in node;
+     *     }
+     *   }
+     *   else if (can CAS slot from node to empty) { // release
+     *     get the item in node;
+     *     set matching item in node;
+     *     release waiting thread;
+     *   }
+     *   // else retry on CAS failure
+     * }
+     *
+     * This is among the simplest forms of a "dual data structure" --
+     * see Scott and Scherer's DISC 04 paper and
+     * http://www.cs.rochester.edu/research/synchronization/pseudocode/duals.html
+     *
+     * This works great in principle. But in practice, like many
+     * algorithms centered on atomic updates to a single location, it
+     * scales horribly when there are more than a few participants
+     * using the same Exchanger. So the implementation instead uses a
+     * form of elimination arena, that spreads out this contention by
+     * arranging that some threads typically use different slots,
+     * while still ensuring that eventually, any two parties will be
+     * able to exchange items. That is, we cannot completely partition
+     * across threads, but instead give threads arena indices that
+     * will on average grow under contention and shrink under lack of
+     * contention. We approach this by defining the Nodes that we need
+     * anyway as ThreadLocals, and include in them per-thread index
+     * and related bookkeeping state. (We can safely reuse per-thread
+     * nodes rather than creating them fresh each time because slots
+     * alternate between pointing to a node vs null, so cannot
+     * encounter ABA problems. However, we do need some care in
+     * resetting them between uses.)
+     *
+     * Implementing an effective arena requires allocating a bunch of
+     * space, so we only do so upon detecting contention (except on
+     * uniprocessors, where they wouldn't help, so aren't used).
+     * Otherwise, exchanges use the single-slot slotExchange method.
+     * On contention, not only must the slots be in different
+     * locations, but the locations must not encounter memory
+     * contention due to being on the same cache line (or more
+     * generally, the same coherence unit).  Because, as of this
+     * writing, there is no way to determine cacheline size, we define
+     * a value that is enough for common platforms.  Additionally,
+     * extra care elsewhere is taken to avoid other false/unintended
+     * sharing and to enhance locality, including adding padding (via
+     * @Contended) to Nodes, embedding "bound" as an Exchanger field.
+     *
+     * The arena starts out with only one used slot. We expand the
+     * effective arena size by tracking collisions; i.e., failed CASes
+     * while trying to exchange. By nature of the above algorithm, the
+     * only kinds of collision that reliably indicate contention are
+     * when two attempted releases collide -- one of two attempted
+     * offers can legitimately fail to CAS without indicating
+     * contention by more than one other thread. (Note: it is possible
+     * but not worthwhile to more precisely detect contention by
+     * reading slot values after CAS failures.)  When a thread has
+     * collided at each slot within the current arena bound, it tries
+     * to expand the arena size by one. We track collisions within
+     * bounds by using a version (sequence) number on the "bound"
+     * field, and conservatively reset collision counts when a
+     * participant notices that bound has been updated (in either
+     * direction).
+     *
+     * The effective arena size is reduced (when there is more than
+     * one slot) by giving up on waiting after a while and trying to
+     * decrement the arena size on expiration. The value of "a while"
+     * is an empirical matter.  We implement by piggybacking on the
+     * use of spin->yield->block that is essential for reasonable
+     * waiting performance anyway -- in a busy exchanger, offers are
+     * usually almost immediately released, in which case context
+     * switching on multiprocessors is extremely slow/wasteful.  Arena
+     * waits just omit the blocking part, and instead cancel. The spin
+     * count is empirically chosen to be a value that avoids blocking
+     * 99% of the time under maximum sustained exchange rates on a
+     * range of test machines. Spins and yields entail some limited
+     * randomness (using a cheap xorshift) to avoid regular patterns
+     * that can induce unproductive grow/shrink cycles. (Using a
+     * pseudorandom also helps regularize spin cycle duration by
+     * making branches unpredictable.)  Also, during an offer, a
+     * waiter can "know" that it will be released when its slot has
+     * changed, but cannot yet proceed until match is set.  In the
+     * mean time it cannot cancel the offer, so instead spins/yields.
+     * Note: It is possible to avoid this secondary check by changing
+     * the linearization point to be a CAS of the match field (as done
+     * in one case in the Scott & Scherer DISC paper), which also
+     * increases asynchrony a bit, at the expense of poorer collision
+     * detection and inability to always reuse per-thread nodes. So
+     * the current scheme is typically a better tradeoff.
+     *
+     * On collisions, indices traverse the arena cyclically in reverse
+     * order, restarting at the maximum index (which will tend to be
+     * sparsest) when bounds change. (On expirations, indices instead
+     * are halved until reaching 0.) It is possible (and has been
+     * tried) to use randomized, prime-value-stepped, or double-hash
+     * style traversal instead of simple cyclic traversal to reduce
+     * bunching.  But empirically, whatever benefits these may have
+     * don't overcome their added overhead: We are managing operations
+     * that occur very quickly unless there is sustained contention,
+     * so simpler/faster control policies work better than more
+     * accurate but slower ones.
+     *
+     * Because we use expiration for arena size control, we cannot
+     * throw TimeoutExceptions in the timed version of the public
+     * exchange method until the arena size has shrunken to zero (or
+     * the arena isn't enabled). This may delay response to timeout
+     * but is still within spec.
+     *
+     * Essentially all of the implementation is in methods
+     * slotExchange and arenaExchange. These have similar overall
+     * structure, but differ in too many details to combine. The
+     * slotExchange method uses the single Exchanger field "slot"
+     * rather than arena array elements. However, it still needs
+     * minimal collision detection to trigger arena construction.
+     * (The messiest part is making sure interrupt status and
+     * InterruptedExceptions come out right during transitions when
+     * both methods may be called. This is done by using null return
+     * as a sentinel to recheck interrupt status.)
+     *
+     * As is too common in this sort of code, methods are monolithic
+     * because most of the logic relies on reads of fields that are
+     * maintained as local variables so can't be nicely factored --
+     * mainly, here, bulky spin->yield->block/cancel code.  Note that
+     * field Node.item is not declared as volatile even though it is
+     * read by releasing threads, because they only do so after CAS
+     * operations that must precede access, and all uses by the owning
+     * thread are otherwise acceptably ordered by other operations.
+     * (Because the actual points of atomicity are slot CASes, it
+     * would also be legal for the write to Node.match in a release to
+     * be weaker than a full volatile write. However, this is not done
+     * because it could allow further postponement of the write,
+     * delaying progress.)
+     */
+
+    /**
+     * The index distance (as a shift value) between any two used slots
+     * in the arena, spacing them out to avoid false sharing.
+     */
+    private static final int ASHIFT = 5;
+
+    /**
+     * The maximum supported arena index. The maximum allocatable
+     * arena size is MMASK + 1. Must be a power of two minus one, less
+     * than (1<<(31-ASHIFT)). The cap of 255 (0xff) more than suffices
+     * for the expected scaling limits of the main algorithms.
+     */
+    private static final int MMASK = 0xff;
+
+    /**
+     * Unit for sequence/version bits of bound field. Each successful
+     * change to the bound also adds SEQ.
+     */
+    private static final int SEQ = MMASK + 1;
+
+    /** The number of CPUs, for sizing and spin control */
+    private static final int NCPU = Runtime.getRuntime().availableProcessors();
+
+    /**
+     * The maximum slot index of the arena: The number of slots that
+     * can in principle hold all threads without contention, or at
+     * most the maximum indexable value.
+     */
+    static final int FULL = (NCPU >= (MMASK << 1)) ? MMASK : NCPU >>> 1;
+
+    /**
+     * The bound for spins while waiting for a match. The actual
+     * number of iterations will on average be about twice this value
+     * due to randomization. Note: Spinning is disabled when NCPU==1.
+     */
+    private static final int SPINS = 1 << 10;
+
+    /**
+     * Value representing null arguments/returns from public
+     * methods. Needed because the API originally didn't disallow null
+     * arguments, which it should have.
+     */
+    private static final Object NULL_ITEM = new Object();
+
+    /**
+     * Sentinel value returned by internal exchange methods upon
+     * timeout, to avoid need for separate timed versions of these
+     * methods.
+     */
+    private static final Object TIMED_OUT = new Object();
+
+    /**
+     * Nodes hold partially exchanged data, plus other per-thread
+     * bookkeeping. Padded via @Contended to reduce memory contention.
+     */
+    @jdk.internal.vm.annotation.Contended static final class Node {
+        int index;              // Arena index
+        int bound;              // Last recorded value of Exchanger.bound
+        int collides;           // Number of CAS failures at current bound
+        int hash;               // Pseudo-random for spins
+        Object item;            // This thread's current item
+        volatile Object match;  // Item provided by releasing thread
+        volatile Thread parked; // Set to this thread when parked, else null
+    }
+
+    /** The corresponding thread local class */
+    static final class Participant extends ThreadLocal<Node> {
+        public Node initialValue() { return new Node(); }
+    }
+
+    /**
+     * Per-thread state.
+     */
+    private final Participant participant;
+
+    /**
+     * Elimination array; null until enabled (within slotExchange).
+     * Element accesses use emulation of volatile gets and CAS.
+     */
+    private volatile Node[] arena;
+
+    /**
+     * Slot used until contention detected.
+     */
+    private volatile Node slot;
+
+    /**
+     * The index of the largest valid arena position, OR'ed with SEQ
+     * number in high bits, incremented on each update.  The initial
+     * update from 0 to SEQ is used to ensure that the arena array is
+     * constructed only once.
+     */
+    private volatile int bound;
+
+    /**
+     * Exchange function when arenas enabled. See above for explanation.
+     *
+     * @param item the (non-null) item to exchange
+     * @param timed true if the wait is timed
+     * @param ns if timed, the maximum wait time, else 0L
+     * @return the other thread's item; or null if interrupted; or
+     * TIMED_OUT if timed and timed out
+     */
+    private final Object arenaExchange(Object item, boolean timed, long ns) {
+        Node[] a = arena;
+        int alen = a.length;
+        Node p = participant.get();
+        for (int i = p.index;;) {                      // access slot at i
+            int b, m, c;
+            int j = (i << ASHIFT) + ((1 << ASHIFT) - 1);
+            if (j < 0 || j >= alen)
+                j = alen - 1;
+            Node q = (Node)AA.getAcquire(a, j);
+            if (q != null && AA.compareAndSet(a, j, q, null)) {
+                Object v = q.item;                     // release
+                q.match = item;
+                Thread w = q.parked;
+                if (w != null)
+                    LockSupport.unpark(w);
+                return v;
+            }
+            else if (i <= (m = (b = bound) & MMASK) && q == null) {
+                p.item = item;                         // offer
+                if (AA.compareAndSet(a, j, null, p)) {
+                    long end = (timed && m == 0) ? System.nanoTime() + ns : 0L;
+                    Thread t = Thread.currentThread(); // wait
+                    for (int h = p.hash, spins = SPINS;;) {
+                        Object v = p.match;
+                        if (v != null) {
+                            MATCH.setRelease(p, null);
+                            p.item = null;             // clear for next use
+                            p.hash = h;
+                            return v;
+                        }
+                        else if (spins > 0) {
+                            h ^= h << 1; h ^= h >>> 3; h ^= h << 10; // xorshift
+                            if (h == 0)                // initialize hash
+                                h = SPINS | (int)t.getId();
+                            else if (h < 0 &&          // approx 50% true
+                                     (--spins & ((SPINS >>> 1) - 1)) == 0)
+                                Thread.yield();        // two yields per wait
+                        }
+                        else if (AA.getAcquire(a, j) != p)
+                            spins = SPINS;       // releaser hasn't set match yet
+                        else if (!t.isInterrupted() && m == 0 &&
+                                 (!timed ||
+                                  (ns = end - System.nanoTime()) > 0L)) {
+                            p.parked = t;              // minimize window
+                            if (AA.getAcquire(a, j) == p) {
+                                if (ns == 0L)
+                                    LockSupport.park(this);
+                                else
+                                    LockSupport.parkNanos(this, ns);
+                            }
+                            p.parked = null;
+                        }
+                        else if (AA.getAcquire(a, j) == p &&
+                                 AA.compareAndSet(a, j, p, null)) {
+                            if (m != 0)                // try to shrink
+                                BOUND.compareAndSet(this, b, b + SEQ - 1);
+                            p.item = null;
+                            p.hash = h;
+                            i = p.index >>>= 1;        // descend
+                            if (Thread.interrupted())
+                                return null;
+                            if (timed && m == 0 && ns <= 0L)
+                                return TIMED_OUT;
+                            break;                     // expired; restart
+                        }
+                    }
+                }
+                else
+                    p.item = null;                     // clear offer
+            }
+            else {
+                if (p.bound != b) {                    // stale; reset
+                    p.bound = b;
+                    p.collides = 0;
+                    i = (i != m || m == 0) ? m : m - 1;
+                }
+                else if ((c = p.collides) < m || m == FULL ||
+                         !BOUND.compareAndSet(this, b, b + SEQ + 1)) {
+                    p.collides = c + 1;
+                    i = (i == 0) ? m : i - 1;          // cyclically traverse
+                }
+                else
+                    i = m + 1;                         // grow
+                p.index = i;
+            }
+        }
+    }
+
+    /**
+     * Exchange function used until arenas enabled. See above for explanation.
+     *
+     * @param item the item to exchange
+     * @param timed true if the wait is timed
+     * @param ns if timed, the maximum wait time, else 0L
+     * @return the other thread's item; or null if either the arena
+     * was enabled or the thread was interrupted before completion; or
+     * TIMED_OUT if timed and timed out
+     */
+    private final Object slotExchange(Object item, boolean timed, long ns) {
+        Node p = participant.get();
+        Thread t = Thread.currentThread();
+        if (t.isInterrupted()) // preserve interrupt status so caller can recheck
+            return null;
+
+        for (Node q;;) {
+            if ((q = slot) != null) {
+                if (SLOT.compareAndSet(this, q, null)) {
+                    Object v = q.item;
+                    q.match = item;
+                    Thread w = q.parked;
+                    if (w != null)
+                        LockSupport.unpark(w);
+                    return v;
+                }
+                // create arena on contention, but continue until slot null
+                if (NCPU > 1 && bound == 0 &&
+                    BOUND.compareAndSet(this, 0, SEQ))
+                    arena = new Node[(FULL + 2) << ASHIFT];
+            }
+            else if (arena != null)
+                return null; // caller must reroute to arenaExchange
+            else {
+                p.item = item;
+                if (SLOT.compareAndSet(this, null, p))
+                    break;
+                p.item = null;
+            }
+        }
+
+        // await release
+        int h = p.hash;
+        long end = timed ? System.nanoTime() + ns : 0L;
+        int spins = (NCPU > 1) ? SPINS : 1;
+        Object v;
+        while ((v = p.match) == null) {
+            if (spins > 0) {
+                h ^= h << 1; h ^= h >>> 3; h ^= h << 10;
+                if (h == 0)
+                    h = SPINS | (int)t.getId();
+                else if (h < 0 && (--spins & ((SPINS >>> 1) - 1)) == 0)
+                    Thread.yield();
+            }
+            else if (slot != p)
+                spins = SPINS;
+            else if (!t.isInterrupted() && arena == null &&
+                     (!timed || (ns = end - System.nanoTime()) > 0L)) {
+                p.parked = t;
+                if (slot == p) {
+                    if (ns == 0L)
+                        LockSupport.park(this);
+                    else
+                        LockSupport.parkNanos(this, ns);
+                }
+                p.parked = null;
+            }
+            else if (SLOT.compareAndSet(this, p, null)) {
+                v = timed && ns <= 0L && !t.isInterrupted() ? TIMED_OUT : null;
+                break;
+            }
+        }
+        MATCH.setRelease(p, null);
+        p.item = null;
+        p.hash = h;
+        return v;
+    }
+
+    /**
+     * Creates a new Exchanger.
+     */
+    public Exchanger() {
+        participant = new Participant();
+    }
+
+    /**
+     * Waits for another thread to arrive at this exchange point (unless
+     * the current thread is {@linkplain Thread#interrupt interrupted}),
+     * and then transfers the given object to it, receiving its object
+     * in return.
+     *
+     * <p>If another thread is already waiting at the exchange point then
+     * it is resumed for thread scheduling purposes and receives the object
+     * passed in by the current thread.  The current thread returns immediately,
+     * receiving the object passed to the exchange by that other thread.
+     *
+     * <p>If no other thread is already waiting at the exchange then the
+     * current thread is disabled for thread scheduling purposes and lies
+     * dormant until one of two things happens:
+     * <ul>
+     * <li>Some other thread enters the exchange; or
+     * <li>Some other thread {@linkplain Thread#interrupt interrupts}
+     * the current thread.
+     * </ul>
+     * <p>If the current thread:
+     * <ul>
+     * <li>has its interrupted status set on entry to this method; or
+     * <li>is {@linkplain Thread#interrupt interrupted} while waiting
+     * for the exchange,
+     * </ul>
+     * then {@link InterruptedException} is thrown and the current thread's
+     * interrupted status is cleared.
+     *
+     * @param x the object to exchange
+     * @return the object provided by the other thread
+     * @throws InterruptedException if the current thread was
+     *         interrupted while waiting
+     */
+    @SuppressWarnings("unchecked")
+    public V exchange(V x) throws InterruptedException {
+        Object v;
+        Node[] a;
+        Object item = (x == null) ? NULL_ITEM : x; // translate null args
+        if (((a = arena) != null ||
+             (v = slotExchange(item, false, 0L)) == null) &&
+            ((Thread.interrupted() || // disambiguates null return
+              (v = arenaExchange(item, false, 0L)) == null)))
+            throw new InterruptedException();
+        return (v == NULL_ITEM) ? null : (V)v;
+    }
+
+    /**
+     * Waits for another thread to arrive at this exchange point (unless
+     * the current thread is {@linkplain Thread#interrupt interrupted} or
+     * the specified waiting time elapses), and then transfers the given
+     * object to it, receiving its object in return.
+     *
+     * <p>If another thread is already waiting at the exchange point then
+     * it is resumed for thread scheduling purposes and receives the object
+     * passed in by the current thread.  The current thread returns immediately,
+     * receiving the object passed to the exchange by that other thread.
+     *
+     * <p>If no other thread is already waiting at the exchange then the
+     * current thread is disabled for thread scheduling purposes and lies
+     * dormant until one of three things happens:
+     * <ul>
+     * <li>Some other thread enters the exchange; or
+     * <li>Some other thread {@linkplain Thread#interrupt interrupts}
+     * the current thread; or
+     * <li>The specified waiting time elapses.
+     * </ul>
+     * <p>If the current thread:
+     * <ul>
+     * <li>has its interrupted status set on entry to this method; or
+     * <li>is {@linkplain Thread#interrupt interrupted} while waiting
+     * for the exchange,
+     * </ul>
+     * then {@link InterruptedException} is thrown and the current thread's
+     * interrupted status is cleared.
+     *
+     * <p>If the specified waiting time elapses then {@link
+     * TimeoutException} is thrown.  If the time is less than or equal
+     * to zero, the method will not wait at all.
+     *
+     * @param x the object to exchange
+     * @param timeout the maximum time to wait
+     * @param unit the time unit of the {@code timeout} argument
+     * @return the object provided by the other thread
+     * @throws InterruptedException if the current thread was
+     *         interrupted while waiting
+     * @throws TimeoutException if the specified waiting time elapses
+     *         before another thread enters the exchange
+     */
+    @SuppressWarnings("unchecked")
+    public V exchange(V x, long timeout, TimeUnit unit)
+        throws InterruptedException, TimeoutException {
+        Object v;
+        Object item = (x == null) ? NULL_ITEM : x;
+        long ns = unit.toNanos(timeout);
+        if ((arena != null ||
+             (v = slotExchange(item, true, ns)) == null) &&
+            ((Thread.interrupted() ||
+              (v = arenaExchange(item, true, ns)) == null)))
+            throw new InterruptedException();
+        if (v == TIMED_OUT)
+            throw new TimeoutException();
+        return (v == NULL_ITEM) ? null : (V)v;
+    }
+
+    // VarHandle mechanics
+    private static final VarHandle BOUND;
+    private static final VarHandle SLOT;
+    private static final VarHandle MATCH;
+    private static final VarHandle AA;
+    static {
+        try {
+            MethodHandles.Lookup l = MethodHandles.lookup();
+            BOUND = l.findVarHandle(Exchanger.class, "bound", int.class);
+            SLOT = l.findVarHandle(Exchanger.class, "slot", Node.class);
+            MATCH = l.findVarHandle(Node.class, "match", Object.class);
+            AA = MethodHandles.arrayElementVarHandle(Node[].class);
+        } catch (ReflectiveOperationException e) {
+            throw new Error(e);
+        }
+    }
+
+}

src/java.base/share/classes/java/util/concurrent/ExecutionException.java

@@ -0,0 +1,92 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent;
+
+/**
+ * Exception thrown when attempting to retrieve the result of a task
+ * that aborted by throwing an exception. This exception can be
+ * inspected using the {@link #getCause()} method.
+ *
+ * @see Future
+ * @since 1.5
+ * @author Doug Lea
+ */
+public class ExecutionException extends Exception {
+    private static final long serialVersionUID = 7830266012832686185L;
+
+    /**
+     * Constructs an {@code ExecutionException} with no detail message.
+     * The cause is not initialized, and may subsequently be
+     * initialized by a call to {@link #initCause(Throwable) initCause}.
+     */
+    protected ExecutionException() { }
+
+    /**
+     * Constructs an {@code ExecutionException} with the specified detail
+     * message. The cause is not initialized, and may subsequently be
+     * initialized by a call to {@link #initCause(Throwable) initCause}.
+     *
+     * @param message the detail message
+     */
+    protected ExecutionException(String message) {
+        super(message);
+    }
+
+    /**
+     * Constructs an {@code ExecutionException} with the specified detail
+     * message and cause.
+     *
+     * @param  message the detail message
+     * @param  cause the cause (which is saved for later retrieval by the
+     *         {@link #getCause()} method)
+     */
+    public ExecutionException(String message, Throwable cause) {
+        super(message, cause);
+    }
+
+    /**
+     * Constructs an {@code ExecutionException} with the specified cause.
+     * The detail message is set to {@code (cause == null ? null :
+     * cause.toString())} (which typically contains the class and
+     * detail message of {@code cause}).
+     *
+     * @param  cause the cause (which is saved for later retrieval by the
+     *         {@link #getCause()} method)
+     */
+    public ExecutionException(Throwable cause) {
+        super(cause);
+    }
+}

src/java.base/share/classes/java/util/concurrent/Executor.java

@@ -0,0 +1,137 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent;
+
+/**
+ * An object that executes submitted {@link Runnable} tasks. This
+ * interface provides a way of decoupling task submission from the
+ * mechanics of how each task will be run, including details of thread
+ * use, scheduling, etc.  An {@code Executor} is normally used
+ * instead of explicitly creating threads. For example, rather than
+ * invoking {@code new Thread(new RunnableTask()).start()} for each
+ * of a set of tasks, you might use:
+ *
+ * <pre> {@code
+ * Executor executor = anExecutor();
+ * executor.execute(new RunnableTask1());
+ * executor.execute(new RunnableTask2());
+ * ...}</pre>
+ *
+ * However, the {@code Executor} interface does not strictly require
+ * that execution be asynchronous. In the simplest case, an executor
+ * can run the submitted task immediately in the caller's thread:
+ *
+ * <pre> {@code
+ * class DirectExecutor implements Executor {
+ *   public void execute(Runnable r) {
+ *     r.run();
+ *   }
+ * }}</pre>
+ *
+ * More typically, tasks are executed in some thread other than the
+ * caller's thread.  The executor below spawns a new thread for each
+ * task.
+ *
+ * <pre> {@code
+ * class ThreadPerTaskExecutor implements Executor {
+ *   public void execute(Runnable r) {
+ *     new Thread(r).start();
+ *   }
+ * }}</pre>
+ *
+ * Many {@code Executor} implementations impose some sort of
+ * limitation on how and when tasks are scheduled.  The executor below
+ * serializes the submission of tasks to a second executor,
+ * illustrating a composite executor.
+ *
+ * <pre> {@code
+ * class SerialExecutor implements Executor {
+ *   final Queue<Runnable> tasks = new ArrayDeque<>();
+ *   final Executor executor;
+ *   Runnable active;
+ *
+ *   SerialExecutor(Executor executor) {
+ *     this.executor = executor;
+ *   }
+ *
+ *   public synchronized void execute(Runnable r) {
+ *     tasks.add(() -> {
+ *       try {
+ *         r.run();
+ *       } finally {
+ *         scheduleNext();
+ *       }
+ *     });
+ *     if (active == null) {
+ *       scheduleNext();
+ *     }
+ *   }
+ *
+ *   protected synchronized void scheduleNext() {
+ *     if ((active = tasks.poll()) != null) {
+ *       executor.execute(active);
+ *     }
+ *   }
+ * }}</pre>
+ *
+ * The {@code Executor} implementations provided in this package
+ * implement {@link ExecutorService}, which is a more extensive
+ * interface.  The {@link ThreadPoolExecutor} class provides an
+ * extensible thread pool implementation. The {@link Executors} class
+ * provides convenient factory methods for these Executors.
+ *
+ * <p>Memory consistency effects: Actions in a thread prior to
+ * submitting a {@code Runnable} object to an {@code Executor}
+ * <a href="package-summary.html#MemoryVisibility"><i>happen-before</i></a>
+ * its execution begins, perhaps in another thread.
+ *
+ * @since 1.5
+ * @author Doug Lea
+ */
+public interface Executor {
+
+    /**
+     * Executes the given command at some time in the future.  The command
+     * may execute in a new thread, in a pooled thread, or in the calling
+     * thread, at the discretion of the {@code Executor} implementation.
+     *
+     * @param command the runnable task
+     * @throws RejectedExecutionException if this task cannot be
+     * accepted for execution
+     * @throws NullPointerException if command is null
+     */
+    void execute(Runnable command);
+}

src/java.base/share/classes/java/util/concurrent/ExecutorCompletionService.java

@@ -0,0 +1,204 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent;
+
+/**
+ * A {@link CompletionService} that uses a supplied {@link Executor}
+ * to execute tasks.  This class arranges that submitted tasks are,
+ * upon completion, placed on a queue accessible using {@code take}.
+ * The class is lightweight enough to be suitable for transient use
+ * when processing groups of tasks.
+ *
+ * <p>
+ *
+ * <b>Usage Examples.</b>
+ *
+ * Suppose you have a set of solvers for a certain problem, each
+ * returning a value of some type {@code Result}, and would like to
+ * run them concurrently, processing the results of each of them that
+ * return a non-null value, in some method {@code use(Result r)}. You
+ * could write this as:
+ *
+ * <pre> {@code
+ * void solve(Executor e,
+ *            Collection<Callable<Result>> solvers)
+ *     throws InterruptedException, ExecutionException {
+ *   CompletionService<Result> cs
+ *       = new ExecutorCompletionService<>(e);
+ *   solvers.forEach(cs::submit);
+ *   for (int i = solvers.size(); i > 0; i--) {
+ *     Result r = cs.take().get();
+ *     if (r != null)
+ *       use(r);
+ *   }
+ * }}</pre>
+ *
+ * Suppose instead that you would like to use the first non-null result
+ * of the set of tasks, ignoring any that encounter exceptions,
+ * and cancelling all other tasks when the first one is ready:
+ *
+ * <pre> {@code
+ * void solve(Executor e,
+ *            Collection<Callable<Result>> solvers)
+ *     throws InterruptedException {
+ *   CompletionService<Result> cs
+ *       = new ExecutorCompletionService<>(e);
+ *   int n = solvers.size();
+ *   List<Future<Result>> futures = new ArrayList<>(n);
+ *   Result result = null;
+ *   try {
+ *     solvers.forEach(solver -> futures.add(cs.submit(solver)));
+ *     for (int i = n; i > 0; i--) {
+ *       try {
+ *         Result r = cs.take().get();
+ *         if (r != null) {
+ *           result = r;
+ *           break;
+ *         }
+ *       } catch (ExecutionException ignore) {}
+ *     }
+ *   } finally {
+ *     futures.forEach(future -> future.cancel(true));
+ *   }
+ *
+ *   if (result != null)
+ *     use(result);
+ * }}</pre>
+ *
+ * @since 1.5
+ */
+public class ExecutorCompletionService<V> implements CompletionService<V> {
+    private final Executor executor;
+    private final AbstractExecutorService aes;
+    private final BlockingQueue<Future<V>> completionQueue;
+
+    /**
+     * FutureTask extension to enqueue upon completion.
+     */
+    private static class QueueingFuture<V> extends FutureTask<Void> {
+        QueueingFuture(RunnableFuture<V> task,
+                       BlockingQueue<Future<V>> completionQueue) {
+            super(task, null);
+            this.task = task;
+            this.completionQueue = completionQueue;
+        }
+        private final Future<V> task;
+        private final BlockingQueue<Future<V>> completionQueue;
+        protected void done() { completionQueue.add(task); }
+    }
+
+    private RunnableFuture<V> newTaskFor(Callable<V> task) {
+        if (aes == null)
+            return new FutureTask<V>(task);
+        else
+            return aes.newTaskFor(task);
+    }
+
+    private RunnableFuture<V> newTaskFor(Runnable task, V result) {
+        if (aes == null)
+            return new FutureTask<V>(task, result);
+        else
+            return aes.newTaskFor(task, result);
+    }
+
+    /**
+     * Creates an ExecutorCompletionService using the supplied
+     * executor for base task execution and a
+     * {@link LinkedBlockingQueue} as a completion queue.
+     *
+     * @param executor the executor to use
+     * @throws NullPointerException if executor is {@code null}
+     */
+    public ExecutorCompletionService(Executor executor) {
+        if (executor == null)
+            throw new NullPointerException();
+        this.executor = executor;
+        this.aes = (executor instanceof AbstractExecutorService) ?
+            (AbstractExecutorService) executor : null;
+        this.completionQueue = new LinkedBlockingQueue<Future<V>>();
+    }
+
+    /**
+     * Creates an ExecutorCompletionService using the supplied
+     * executor for base task execution and the supplied queue as its
+     * completion queue.
+     *
+     * @param executor the executor to use
+     * @param completionQueue the queue to use as the completion queue
+     *        normally one dedicated for use by this service. This
+     *        queue is treated as unbounded -- failed attempted
+     *        {@code Queue.add} operations for completed tasks cause
+     *        them not to be retrievable.
+     * @throws NullPointerException if executor or completionQueue are {@code null}
+     */
+    public ExecutorCompletionService(Executor executor,
+                                     BlockingQueue<Future<V>> completionQueue) {
+        if (executor == null || completionQueue == null)
+            throw new NullPointerException();
+        this.executor = executor;
+        this.aes = (executor instanceof AbstractExecutorService) ?
+            (AbstractExecutorService) executor : null;
+        this.completionQueue = completionQueue;
+    }
+
+    public Future<V> submit(Callable<V> task) {
+        if (task == null) throw new NullPointerException();
+        RunnableFuture<V> f = newTaskFor(task);
+        executor.execute(new QueueingFuture<V>(f, completionQueue));
+        return f;
+    }
+
+    public Future<V> submit(Runnable task, V result) {
+        if (task == null) throw new NullPointerException();
+        RunnableFuture<V> f = newTaskFor(task, result);
+        executor.execute(new QueueingFuture<V>(f, completionQueue));
+        return f;
+    }
+
+    public Future<V> take() throws InterruptedException {
+        return completionQueue.take();
+    }
+
+    public Future<V> poll() {
+        return completionQueue.poll();
+    }
+
+    public Future<V> poll(long timeout, TimeUnit unit)
+            throws InterruptedException {
+        return completionQueue.poll(timeout, unit);
+    }
+
+}

src/java.base/share/classes/java/util/concurrent/ExecutorService.java

@@ -0,0 +1,371 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent;
+
+import java.util.Collection;
+import java.util.List;
+
+/**
+ * An {@link Executor} that provides methods to manage termination and
+ * methods that can produce a {@link Future} for tracking progress of
+ * one or more asynchronous tasks.
+ *
+ * <p>An {@code ExecutorService} can be shut down, which will cause
+ * it to reject new tasks.  Two different methods are provided for
+ * shutting down an {@code ExecutorService}. The {@link #shutdown}
+ * method will allow previously submitted tasks to execute before
+ * terminating, while the {@link #shutdownNow} method prevents waiting
+ * tasks from starting and attempts to stop currently executing tasks.
+ * Upon termination, an executor has no tasks actively executing, no
+ * tasks awaiting execution, and no new tasks can be submitted.  An
+ * unused {@code ExecutorService} should be shut down to allow
+ * reclamation of its resources.
+ *
+ * <p>Method {@code submit} extends base method {@link
+ * Executor#execute(Runnable)} by creating and returning a {@link Future}
+ * that can be used to cancel execution and/or wait for completion.
+ * Methods {@code invokeAny} and {@code invokeAll} perform the most
+ * commonly useful forms of bulk execution, executing a collection of
+ * tasks and then waiting for at least one, or all, to
+ * complete. (Class {@link ExecutorCompletionService} can be used to
+ * write customized variants of these methods.)
+ *
+ * <p>The {@link Executors} class provides factory methods for the
+ * executor services provided in this package.
+ *
+ * <h3>Usage Examples</h3>
+ *
+ * Here is a sketch of a network service in which threads in a thread
+ * pool service incoming requests. It uses the preconfigured {@link
+ * Executors#newFixedThreadPool} factory method:
+ *
+ * <pre> {@code
+ * class NetworkService implements Runnable {
+ *   private final ServerSocket serverSocket;
+ *   private final ExecutorService pool;
+ *
+ *   public NetworkService(int port, int poolSize)
+ *       throws IOException {
+ *     serverSocket = new ServerSocket(port);
+ *     pool = Executors.newFixedThreadPool(poolSize);
+ *   }
+ *
+ *   public void run() { // run the service
+ *     try {
+ *       for (;;) {
+ *         pool.execute(new Handler(serverSocket.accept()));
+ *       }
+ *     } catch (IOException ex) {
+ *       pool.shutdown();
+ *     }
+ *   }
+ * }
+ *
+ * class Handler implements Runnable {
+ *   private final Socket socket;
+ *   Handler(Socket socket) { this.socket = socket; }
+ *   public void run() {
+ *     // read and service request on socket
+ *   }
+ * }}</pre>
+ *
+ * The following method shuts down an {@code ExecutorService} in two phases,
+ * first by calling {@code shutdown} to reject incoming tasks, and then
+ * calling {@code shutdownNow}, if necessary, to cancel any lingering tasks:
+ *
+ * <pre> {@code
+ * void shutdownAndAwaitTermination(ExecutorService pool) {
+ *   pool.shutdown(); // Disable new tasks from being submitted
+ *   try {
+ *     // Wait a while for existing tasks to terminate
+ *     if (!pool.awaitTermination(60, TimeUnit.SECONDS)) {
+ *       pool.shutdownNow(); // Cancel currently executing tasks
+ *       // Wait a while for tasks to respond to being cancelled
+ *       if (!pool.awaitTermination(60, TimeUnit.SECONDS))
+ *           System.err.println("Pool did not terminate");
+ *     }
+ *   } catch (InterruptedException ie) {
+ *     // (Re-)Cancel if current thread also interrupted
+ *     pool.shutdownNow();
+ *     // Preserve interrupt status
+ *     Thread.currentThread().interrupt();
+ *   }
+ * }}</pre>
+ *
+ * <p>Memory consistency effects: Actions in a thread prior to the
+ * submission of a {@code Runnable} or {@code Callable} task to an
+ * {@code ExecutorService}
+ * <a href="package-summary.html#MemoryVisibility"><i>happen-before</i></a>
+ * any actions taken by that task, which in turn <i>happen-before</i> the
+ * result is retrieved via {@code Future.get()}.
+ *
+ * @since 1.5
+ * @author Doug Lea
+ */
+public interface ExecutorService extends Executor {
+
+    /**
+     * Initiates an orderly shutdown in which previously submitted
+     * tasks are executed, but no new tasks will be accepted.
+     * Invocation has no additional effect if already shut down.
+     *
+     * <p>This method does not wait for previously submitted tasks to
+     * complete execution.  Use {@link #awaitTermination awaitTermination}
+     * to do that.
+     *
+     * @throws SecurityException if a security manager exists and
+     *         shutting down this ExecutorService may manipulate
+     *         threads that the caller is not permitted to modify
+     *         because it does not hold {@link
+     *         java.lang.RuntimePermission}{@code ("modifyThread")},
+     *         or the security manager's {@code checkAccess} method
+     *         denies access.
+     */
+    void shutdown();
+
+    /**
+     * Attempts to stop all actively executing tasks, halts the
+     * processing of waiting tasks, and returns a list of the tasks
+     * that were awaiting execution.
+     *
+     * <p>This method does not wait for actively executing tasks to
+     * terminate.  Use {@link #awaitTermination awaitTermination} to
+     * do that.
+     *
+     * <p>There are no guarantees beyond best-effort attempts to stop
+     * processing actively executing tasks.  For example, typical
+     * implementations will cancel via {@link Thread#interrupt}, so any
+     * task that fails to respond to interrupts may never terminate.
+     *
+     * @return list of tasks that never commenced execution
+     * @throws SecurityException if a security manager exists and
+     *         shutting down this ExecutorService may manipulate
+     *         threads that the caller is not permitted to modify
+     *         because it does not hold {@link
+     *         java.lang.RuntimePermission}{@code ("modifyThread")},
+     *         or the security manager's {@code checkAccess} method
+     *         denies access.
+     */
+    List<Runnable> shutdownNow();
+
+    /**
+     * Returns {@code true} if this executor has been shut down.
+     *
+     * @return {@code true} if this executor has been shut down
+     */
+    boolean isShutdown();
+
+    /**
+     * Returns {@code true} if all tasks have completed following shut down.
+     * Note that {@code isTerminated} is never {@code true} unless
+     * either {@code shutdown} or {@code shutdownNow} was called first.
+     *
+     * @return {@code true} if all tasks have completed following shut down
+     */
+    boolean isTerminated();
+
+    /**
+     * Blocks until all tasks have completed execution after a shutdown
+     * request, or the timeout occurs, or the current thread is
+     * interrupted, whichever happens first.
+     *
+     * @param timeout the maximum time to wait
+     * @param unit the time unit of the timeout argument
+     * @return {@code true} if this executor terminated and
+     *         {@code false} if the timeout elapsed before termination
+     * @throws InterruptedException if interrupted while waiting
+     */
+    boolean awaitTermination(long timeout, TimeUnit unit)
+        throws InterruptedException;
+
+    /**
+     * Submits a value-returning task for execution and returns a
+     * Future representing the pending results of the task. The
+     * Future's {@code get} method will return the task's result upon
+     * successful completion.
+     *
+     * <p>
+     * If you would like to immediately block waiting
+     * for a task, you can use constructions of the form
+     * {@code result = exec.submit(aCallable).get();}
+     *
+     * <p>Note: The {@link Executors} class includes a set of methods
+     * that can convert some other common closure-like objects,
+     * for example, {@link java.security.PrivilegedAction} to
+     * {@link Callable} form so they can be submitted.
+     *
+     * @param task the task to submit
+     * @param <T> the type of the task's result
+     * @return a Future representing pending completion of the task
+     * @throws RejectedExecutionException if the task cannot be
+     *         scheduled for execution
+     * @throws NullPointerException if the task is null
+     */
+    <T> Future<T> submit(Callable<T> task);
+
+    /**
+     * Submits a Runnable task for execution and returns a Future
+     * representing that task. The Future's {@code get} method will
+     * return the given result upon successful completion.
+     *
+     * @param task the task to submit
+     * @param result the result to return
+     * @param <T> the type of the result
+     * @return a Future representing pending completion of the task
+     * @throws RejectedExecutionException if the task cannot be
+     *         scheduled for execution
+     * @throws NullPointerException if the task is null
+     */
+    <T> Future<T> submit(Runnable task, T result);
+
+    /**
+     * Submits a Runnable task for execution and returns a Future
+     * representing that task. The Future's {@code get} method will
+     * return {@code null} upon <em>successful</em> completion.
+     *
+     * @param task the task to submit
+     * @return a Future representing pending completion of the task
+     * @throws RejectedExecutionException if the task cannot be
+     *         scheduled for execution
+     * @throws NullPointerException if the task is null
+     */
+    Future<?> submit(Runnable task);
+
+    /**
+     * Executes the given tasks, returning a list of Futures holding
+     * their status and results when all complete.
+     * {@link Future#isDone} is {@code true} for each
+     * element of the returned list.
+     * Note that a <em>completed</em> task could have
+     * terminated either normally or by throwing an exception.
+     * The results of this method are undefined if the given
+     * collection is modified while this operation is in progress.
+     *
+     * @param tasks the collection of tasks
+     * @param <T> the type of the values returned from the tasks
+     * @return a list of Futures representing the tasks, in the same
+     *         sequential order as produced by the iterator for the
+     *         given task list, each of which has completed
+     * @throws InterruptedException if interrupted while waiting, in
+     *         which case unfinished tasks are cancelled
+     * @throws NullPointerException if tasks or any of its elements are {@code null}
+     * @throws RejectedExecutionException if any task cannot be
+     *         scheduled for execution
+     */
+    <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks)
+        throws InterruptedException;
+
+    /**
+     * Executes the given tasks, returning a list of Futures holding
+     * their status and results
+     * when all complete or the timeout expires, whichever happens first.
+     * {@link Future#isDone} is {@code true} for each
+     * element of the returned list.
+     * Upon return, tasks that have not completed are cancelled.
+     * Note that a <em>completed</em> task could have
+     * terminated either normally or by throwing an exception.
+     * The results of this method are undefined if the given
+     * collection is modified while this operation is in progress.
+     *
+     * @param tasks the collection of tasks
+     * @param timeout the maximum time to wait
+     * @param unit the time unit of the timeout argument
+     * @param <T> the type of the values returned from the tasks
+     * @return a list of Futures representing the tasks, in the same
+     *         sequential order as produced by the iterator for the
+     *         given task list. If the operation did not time out,
+     *         each task will have completed. If it did time out, some
+     *         of these tasks will not have completed.
+     * @throws InterruptedException if interrupted while waiting, in
+     *         which case unfinished tasks are cancelled
+     * @throws NullPointerException if tasks, any of its elements, or
+     *         unit are {@code null}
+     * @throws RejectedExecutionException if any task cannot be scheduled
+     *         for execution
+     */
+    <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks,
+                                  long timeout, TimeUnit unit)
+        throws InterruptedException;
+
+    /**
+     * Executes the given tasks, returning the result
+     * of one that has completed successfully (i.e., without throwing
+     * an exception), if any do. Upon normal or exceptional return,
+     * tasks that have not completed are cancelled.
+     * The results of this method are undefined if the given
+     * collection is modified while this operation is in progress.
+     *
+     * @param tasks the collection of tasks
+     * @param <T> the type of the values returned from the tasks
+     * @return the result returned by one of the tasks
+     * @throws InterruptedException if interrupted while waiting
+     * @throws NullPointerException if tasks or any element task
+     *         subject to execution is {@code null}
+     * @throws IllegalArgumentException if tasks is empty
+     * @throws ExecutionException if no task successfully completes
+     * @throws RejectedExecutionException if tasks cannot be scheduled
+     *         for execution
+     */
+    <T> T invokeAny(Collection<? extends Callable<T>> tasks)
+        throws InterruptedException, ExecutionException;
+
+    /**
+     * Executes the given tasks, returning the result
+     * of one that has completed successfully (i.e., without throwing
+     * an exception), if any do before the given timeout elapses.
+     * Upon normal or exceptional return, tasks that have not
+     * completed are cancelled.
+     * The results of this method are undefined if the given
+     * collection is modified while this operation is in progress.
+     *
+     * @param tasks the collection of tasks
+     * @param timeout the maximum time to wait
+     * @param unit the time unit of the timeout argument
+     * @param <T> the type of the values returned from the tasks
+     * @return the result returned by one of the tasks
+     * @throws InterruptedException if interrupted while waiting
+     * @throws NullPointerException if tasks, or unit, or any element
+     *         task subject to execution is {@code null}
+     * @throws TimeoutException if the given timeout elapses before
+     *         any task successfully completes
+     * @throws ExecutionException if no task successfully completes
+     * @throws RejectedExecutionException if tasks cannot be scheduled
+     *         for execution
+     */
+    <T> T invokeAny(Collection<? extends Callable<T>> tasks,
+                    long timeout, TimeUnit unit)
+        throws InterruptedException, ExecutionException, TimeoutException;
+}

src/java.base/share/classes/java/util/concurrent/Executors.java

@@ -0,0 +1,750 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent;
+
+import java.security.AccessControlContext;
+import java.security.AccessControlException;
+import java.security.AccessController;
+import java.security.PrivilegedAction;
+import java.security.PrivilegedActionException;
+import java.security.PrivilegedExceptionAction;
+import java.util.Collection;
+import java.util.List;
+import java.util.concurrent.atomic.AtomicInteger;
+import sun.security.util.SecurityConstants;
+
+/**
+ * Factory and utility methods for {@link Executor}, {@link
+ * ExecutorService}, {@link ScheduledExecutorService}, {@link
+ * ThreadFactory}, and {@link Callable} classes defined in this
+ * package. This class supports the following kinds of methods:
+ *
+ * <ul>
+ *   <li>Methods that create and return an {@link ExecutorService}
+ *       set up with commonly useful configuration settings.
+ *   <li>Methods that create and return a {@link ScheduledExecutorService}
+ *       set up with commonly useful configuration settings.
+ *   <li>Methods that create and return a "wrapped" ExecutorService, that
+ *       disables reconfiguration by making implementation-specific methods
+ *       inaccessible.
+ *   <li>Methods that create and return a {@link ThreadFactory}
+ *       that sets newly created threads to a known state.
+ *   <li>Methods that create and return a {@link Callable}
+ *       out of other closure-like forms, so they can be used
+ *       in execution methods requiring {@code Callable}.
+ * </ul>
+ *
+ * @since 1.5
+ * @author Doug Lea
+ */
+public class Executors {
+
+    /**
+     * Creates a thread pool that reuses a fixed number of threads
+     * operating off a shared unbounded queue.  At any point, at most
+     * {@code nThreads} threads will be active processing tasks.
+     * If additional tasks are submitted when all threads are active,
+     * they will wait in the queue until a thread is available.
+     * If any thread terminates due to a failure during execution
+     * prior to shutdown, a new one will take its place if needed to
+     * execute subsequent tasks.  The threads in the pool will exist
+     * until it is explicitly {@link ExecutorService#shutdown shutdown}.
+     *
+     * @param nThreads the number of threads in the pool
+     * @return the newly created thread pool
+     * @throws IllegalArgumentException if {@code nThreads <= 0}
+     */
+    public static ExecutorService newFixedThreadPool(int nThreads) {
+        return new ThreadPoolExecutor(nThreads, nThreads,
+                                      0L, TimeUnit.MILLISECONDS,
+                                      new LinkedBlockingQueue<Runnable>());
+    }
+
+    /**
+     * Creates a thread pool that maintains enough threads to support
+     * the given parallelism level, and may use multiple queues to
+     * reduce contention. The parallelism level corresponds to the
+     * maximum number of threads actively engaged in, or available to
+     * engage in, task processing. The actual number of threads may
+     * grow and shrink dynamically. A work-stealing pool makes no
+     * guarantees about the order in which submitted tasks are
+     * executed.
+     *
+     * @param parallelism the targeted parallelism level
+     * @return the newly created thread pool
+     * @throws IllegalArgumentException if {@code parallelism <= 0}
+     * @since 1.8
+     */
+    public static ExecutorService newWorkStealingPool(int parallelism) {
+        return new ForkJoinPool
+            (parallelism,
+             ForkJoinPool.defaultForkJoinWorkerThreadFactory,
+             null, true);
+    }
+
+    /**
+     * Creates a work-stealing thread pool using the number of
+     * {@linkplain Runtime#availableProcessors available processors}
+     * as its target parallelism level.
+     *
+     * @return the newly created thread pool
+     * @see #newWorkStealingPool(int)
+     * @since 1.8
+     */
+    public static ExecutorService newWorkStealingPool() {
+        return new ForkJoinPool
+            (Runtime.getRuntime().availableProcessors(),
+             ForkJoinPool.defaultForkJoinWorkerThreadFactory,
+             null, true);
+    }
+
+    /**
+     * Creates a thread pool that reuses a fixed number of threads
+     * operating off a shared unbounded queue, using the provided
+     * ThreadFactory to create new threads when needed.  At any point,
+     * at most {@code nThreads} threads will be active processing
+     * tasks.  If additional tasks are submitted when all threads are
+     * active, they will wait in the queue until a thread is
+     * available.  If any thread terminates due to a failure during
+     * execution prior to shutdown, a new one will take its place if
+     * needed to execute subsequent tasks.  The threads in the pool will
+     * exist until it is explicitly {@link ExecutorService#shutdown
+     * shutdown}.
+     *
+     * @param nThreads the number of threads in the pool
+     * @param threadFactory the factory to use when creating new threads
+     * @return the newly created thread pool
+     * @throws NullPointerException if threadFactory is null
+     * @throws IllegalArgumentException if {@code nThreads <= 0}
+     */
+    public static ExecutorService newFixedThreadPool(int nThreads, ThreadFactory threadFactory) {
+        return new ThreadPoolExecutor(nThreads, nThreads,
+                                      0L, TimeUnit.MILLISECONDS,
+                                      new LinkedBlockingQueue<Runnable>(),
+                                      threadFactory);
+    }
+
+    /**
+     * Creates an Executor that uses a single worker thread operating
+     * off an unbounded queue. (Note however that if this single
+     * thread terminates due to a failure during execution prior to
+     * shutdown, a new one will take its place if needed to execute
+     * subsequent tasks.)  Tasks are guaranteed to execute
+     * sequentially, and no more than one task will be active at any
+     * given time. Unlike the otherwise equivalent
+     * {@code newFixedThreadPool(1)} the returned executor is
+     * guaranteed not to be reconfigurable to use additional threads.
+     *
+     * @return the newly created single-threaded Executor
+     */
+    public static ExecutorService newSingleThreadExecutor() {
+        return new FinalizableDelegatedExecutorService
+            (new ThreadPoolExecutor(1, 1,
+                                    0L, TimeUnit.MILLISECONDS,
+                                    new LinkedBlockingQueue<Runnable>()));
+    }
+
+    /**
+     * Creates an Executor that uses a single worker thread operating
+     * off an unbounded queue, and uses the provided ThreadFactory to
+     * create a new thread when needed. Unlike the otherwise
+     * equivalent {@code newFixedThreadPool(1, threadFactory)} the
+     * returned executor is guaranteed not to be reconfigurable to use
+     * additional threads.
+     *
+     * @param threadFactory the factory to use when creating new
+     * threads
+     *
+     * @return the newly created single-threaded Executor
+     * @throws NullPointerException if threadFactory is null
+     */
+    public static ExecutorService newSingleThreadExecutor(ThreadFactory threadFactory) {
+        return new FinalizableDelegatedExecutorService
+            (new ThreadPoolExecutor(1, 1,
+                                    0L, TimeUnit.MILLISECONDS,
+                                    new LinkedBlockingQueue<Runnable>(),
+                                    threadFactory));
+    }
+
+    /**
+     * Creates a thread pool that creates new threads as needed, but
+     * will reuse previously constructed threads when they are
+     * available.  These pools will typically improve the performance
+     * of programs that execute many short-lived asynchronous tasks.
+     * Calls to {@code execute} will reuse previously constructed
+     * threads if available. If no existing thread is available, a new
+     * thread will be created and added to the pool. Threads that have
+     * not been used for sixty seconds are terminated and removed from
+     * the cache. Thus, a pool that remains idle for long enough will
+     * not consume any resources. Note that pools with similar
+     * properties but different details (for example, timeout parameters)
+     * may be created using {@link ThreadPoolExecutor} constructors.
+     *
+     * @return the newly created thread pool
+     */
+    public static ExecutorService newCachedThreadPool() {
+        return new ThreadPoolExecutor(0, Integer.MAX_VALUE,
+                                      60L, TimeUnit.SECONDS,
+                                      new SynchronousQueue<Runnable>());
+    }
+
+    /**
+     * Creates a thread pool that creates new threads as needed, but
+     * will reuse previously constructed threads when they are
+     * available, and uses the provided
+     * ThreadFactory to create new threads when needed.
+     * @param threadFactory the factory to use when creating new threads
+     * @return the newly created thread pool
+     * @throws NullPointerException if threadFactory is null
+     */
+    public static ExecutorService newCachedThreadPool(ThreadFactory threadFactory) {
+        return new ThreadPoolExecutor(0, Integer.MAX_VALUE,
+                                      60L, TimeUnit.SECONDS,
+                                      new SynchronousQueue<Runnable>(),
+                                      threadFactory);
+    }
+
+    /**
+     * Creates a single-threaded executor that can schedule commands
+     * to run after a given delay, or to execute periodically.
+     * (Note however that if this single
+     * thread terminates due to a failure during execution prior to
+     * shutdown, a new one will take its place if needed to execute
+     * subsequent tasks.)  Tasks are guaranteed to execute
+     * sequentially, and no more than one task will be active at any
+     * given time. Unlike the otherwise equivalent
+     * {@code newScheduledThreadPool(1)} the returned executor is
+     * guaranteed not to be reconfigurable to use additional threads.
+     * @return the newly created scheduled executor
+     */
+    public static ScheduledExecutorService newSingleThreadScheduledExecutor() {
+        return new DelegatedScheduledExecutorService
+            (new ScheduledThreadPoolExecutor(1));
+    }
+
+    /**
+     * Creates a single-threaded executor that can schedule commands
+     * to run after a given delay, or to execute periodically.  (Note
+     * however that if this single thread terminates due to a failure
+     * during execution prior to shutdown, a new one will take its
+     * place if needed to execute subsequent tasks.)  Tasks are
+     * guaranteed to execute sequentially, and no more than one task
+     * will be active at any given time. Unlike the otherwise
+     * equivalent {@code newScheduledThreadPool(1, threadFactory)}
+     * the returned executor is guaranteed not to be reconfigurable to
+     * use additional threads.
+     * @param threadFactory the factory to use when creating new
+     * threads
+     * @return a newly created scheduled executor
+     * @throws NullPointerException if threadFactory is null
+     */
+    public static ScheduledExecutorService newSingleThreadScheduledExecutor(ThreadFactory threadFactory) {
+        return new DelegatedScheduledExecutorService
+            (new ScheduledThreadPoolExecutor(1, threadFactory));
+    }
+
+    /**
+     * Creates a thread pool that can schedule commands to run after a
+     * given delay, or to execute periodically.
+     * @param corePoolSize the number of threads to keep in the pool,
+     * even if they are idle
+     * @return a newly created scheduled thread pool
+     * @throws IllegalArgumentException if {@code corePoolSize < 0}
+     */
+    public static ScheduledExecutorService newScheduledThreadPool(int corePoolSize) {
+        return new ScheduledThreadPoolExecutor(corePoolSize);
+    }
+
+    /**
+     * Creates a thread pool that can schedule commands to run after a
+     * given delay, or to execute periodically.
+     * @param corePoolSize the number of threads to keep in the pool,
+     * even if they are idle
+     * @param threadFactory the factory to use when the executor
+     * creates a new thread
+     * @return a newly created scheduled thread pool
+     * @throws IllegalArgumentException if {@code corePoolSize < 0}
+     * @throws NullPointerException if threadFactory is null
+     */
+    public static ScheduledExecutorService newScheduledThreadPool(
+            int corePoolSize, ThreadFactory threadFactory) {
+        return new ScheduledThreadPoolExecutor(corePoolSize, threadFactory);
+    }
+
+    /**
+     * Returns an object that delegates all defined {@link
+     * ExecutorService} methods to the given executor, but not any
+     * other methods that might otherwise be accessible using
+     * casts. This provides a way to safely "freeze" configuration and
+     * disallow tuning of a given concrete implementation.
+     * @param executor the underlying implementation
+     * @return an {@code ExecutorService} instance
+     * @throws NullPointerException if executor null
+     */
+    public static ExecutorService unconfigurableExecutorService(ExecutorService executor) {
+        if (executor == null)
+            throw new NullPointerException();
+        return new DelegatedExecutorService(executor);
+    }
+
+    /**
+     * Returns an object that delegates all defined {@link
+     * ScheduledExecutorService} methods to the given executor, but
+     * not any other methods that might otherwise be accessible using
+     * casts. This provides a way to safely "freeze" configuration and
+     * disallow tuning of a given concrete implementation.
+     * @param executor the underlying implementation
+     * @return a {@code ScheduledExecutorService} instance
+     * @throws NullPointerException if executor null
+     */
+    public static ScheduledExecutorService unconfigurableScheduledExecutorService(ScheduledExecutorService executor) {
+        if (executor == null)
+            throw new NullPointerException();
+        return new DelegatedScheduledExecutorService(executor);
+    }
+
+    /**
+     * Returns a default thread factory used to create new threads.
+     * This factory creates all new threads used by an Executor in the
+     * same {@link ThreadGroup}. If there is a {@link
+     * java.lang.SecurityManager}, it uses the group of {@link
+     * System#getSecurityManager}, else the group of the thread
+     * invoking this {@code defaultThreadFactory} method. Each new
+     * thread is created as a non-daemon thread with priority set to
+     * the smaller of {@code Thread.NORM_PRIORITY} and the maximum
+     * priority permitted in the thread group.  New threads have names
+     * accessible via {@link Thread#getName} of
+     * <em>pool-N-thread-M</em>, where <em>N</em> is the sequence
+     * number of this factory, and <em>M</em> is the sequence number
+     * of the thread created by this factory.
+     * @return a thread factory
+     */
+    public static ThreadFactory defaultThreadFactory() {
+        return new DefaultThreadFactory();
+    }
+
+    /**
+     * Returns a thread factory used to create new threads that
+     * have the same permissions as the current thread.
+     * This factory creates threads with the same settings as {@link
+     * Executors#defaultThreadFactory}, additionally setting the
+     * AccessControlContext and contextClassLoader of new threads to
+     * be the same as the thread invoking this
+     * {@code privilegedThreadFactory} method.  A new
+     * {@code privilegedThreadFactory} can be created within an
+     * {@link AccessController#doPrivileged AccessController.doPrivileged}
+     * action setting the current thread's access control context to
+     * create threads with the selected permission settings holding
+     * within that action.
+     *
+     * <p>Note that while tasks running within such threads will have
+     * the same access control and class loader settings as the
+     * current thread, they need not have the same {@link
+     * java.lang.ThreadLocal} or {@link
+     * java.lang.InheritableThreadLocal} values. If necessary,
+     * particular values of thread locals can be set or reset before
+     * any task runs in {@link ThreadPoolExecutor} subclasses using
+     * {@link ThreadPoolExecutor#beforeExecute(Thread, Runnable)}.
+     * Also, if it is necessary to initialize worker threads to have
+     * the same InheritableThreadLocal settings as some other
+     * designated thread, you can create a custom ThreadFactory in
+     * which that thread waits for and services requests to create
+     * others that will inherit its values.
+     *
+     * @return a thread factory
+     * @throws AccessControlException if the current access control
+     * context does not have permission to both get and set context
+     * class loader
+     */
+    public static ThreadFactory privilegedThreadFactory() {
+        return new PrivilegedThreadFactory();
+    }
+
+    /**
+     * Returns a {@link Callable} object that, when
+     * called, runs the given task and returns the given result.  This
+     * can be useful when applying methods requiring a
+     * {@code Callable} to an otherwise resultless action.
+     * @param task the task to run
+     * @param result the result to return
+     * @param <T> the type of the result
+     * @return a callable object
+     * @throws NullPointerException if task null
+     */
+    public static <T> Callable<T> callable(Runnable task, T result) {
+        if (task == null)
+            throw new NullPointerException();
+        return new RunnableAdapter<T>(task, result);
+    }
+
+    /**
+     * Returns a {@link Callable} object that, when
+     * called, runs the given task and returns {@code null}.
+     * @param task the task to run
+     * @return a callable object
+     * @throws NullPointerException if task null
+     */
+    public static Callable<Object> callable(Runnable task) {
+        if (task == null)
+            throw new NullPointerException();
+        return new RunnableAdapter<Object>(task, null);
+    }
+
+    /**
+     * Returns a {@link Callable} object that, when
+     * called, runs the given privileged action and returns its result.
+     * @param action the privileged action to run
+     * @return a callable object
+     * @throws NullPointerException if action null
+     */
+    public static Callable<Object> callable(final PrivilegedAction<?> action) {
+        if (action == null)
+            throw new NullPointerException();
+        return new Callable<Object>() {
+            public Object call() { return action.run(); }};
+    }
+
+    /**
+     * Returns a {@link Callable} object that, when
+     * called, runs the given privileged exception action and returns
+     * its result.
+     * @param action the privileged exception action to run
+     * @return a callable object
+     * @throws NullPointerException if action null
+     */
+    public static Callable<Object> callable(final PrivilegedExceptionAction<?> action) {
+        if (action == null)
+            throw new NullPointerException();
+        return new Callable<Object>() {
+            public Object call() throws Exception { return action.run(); }};
+    }
+
+    /**
+     * Returns a {@link Callable} object that will, when called,
+     * execute the given {@code callable} under the current access
+     * control context. This method should normally be invoked within
+     * an {@link AccessController#doPrivileged AccessController.doPrivileged}
+     * action to create callables that will, if possible, execute
+     * under the selected permission settings holding within that
+     * action; or if not possible, throw an associated {@link
+     * AccessControlException}.
+     * @param callable the underlying task
+     * @param <T> the type of the callable's result
+     * @return a callable object
+     * @throws NullPointerException if callable null
+     */
+    public static <T> Callable<T> privilegedCallable(Callable<T> callable) {
+        if (callable == null)
+            throw new NullPointerException();
+        return new PrivilegedCallable<T>(callable);
+    }
+
+    /**
+     * Returns a {@link Callable} object that will, when called,
+     * execute the given {@code callable} under the current access
+     * control context, with the current context class loader as the
+     * context class loader. This method should normally be invoked
+     * within an
+     * {@link AccessController#doPrivileged AccessController.doPrivileged}
+     * action to create callables that will, if possible, execute
+     * under the selected permission settings holding within that
+     * action; or if not possible, throw an associated {@link
+     * AccessControlException}.
+     *
+     * @param callable the underlying task
+     * @param <T> the type of the callable's result
+     * @return a callable object
+     * @throws NullPointerException if callable null
+     * @throws AccessControlException if the current access control
+     * context does not have permission to both set and get context
+     * class loader
+     */
+    public static <T> Callable<T> privilegedCallableUsingCurrentClassLoader(Callable<T> callable) {
+        if (callable == null)
+            throw new NullPointerException();
+        return new PrivilegedCallableUsingCurrentClassLoader<T>(callable);
+    }
+
+    // Non-public classes supporting the public methods
+
+    /**
+     * A callable that runs given task and returns given result.
+     */
+    private static final class RunnableAdapter<T> implements Callable<T> {
+        private final Runnable task;
+        private final T result;
+        RunnableAdapter(Runnable task, T result) {
+            this.task = task;
+            this.result = result;
+        }
+        public T call() {
+            task.run();
+            return result;
+        }
+    }
+
+    /**
+     * A callable that runs under established access control settings.
+     */
+    private static final class PrivilegedCallable<T> implements Callable<T> {
+        final Callable<T> task;
+        final AccessControlContext acc;
+
+        PrivilegedCallable(Callable<T> task) {
+            this.task = task;
+            this.acc = AccessController.getContext();
+        }
+
+        public T call() throws Exception {
+            try {
+                return AccessController.doPrivileged(
+                    new PrivilegedExceptionAction<T>() {
+                        public T run() throws Exception {
+                            return task.call();
+                        }
+                    }, acc);
+            } catch (PrivilegedActionException e) {
+                throw e.getException();
+            }
+        }
+    }
+
+    /**
+     * A callable that runs under established access control settings and
+     * current ClassLoader.
+     */
+    private static final class PrivilegedCallableUsingCurrentClassLoader<T>
+            implements Callable<T> {
+        final Callable<T> task;
+        final AccessControlContext acc;
+        final ClassLoader ccl;
+
+        PrivilegedCallableUsingCurrentClassLoader(Callable<T> task) {
+            SecurityManager sm = System.getSecurityManager();
+            if (sm != null) {
+                // Calls to getContextClassLoader from this class
+                // never trigger a security check, but we check
+                // whether our callers have this permission anyways.
+                sm.checkPermission(SecurityConstants.GET_CLASSLOADER_PERMISSION);
+
+                // Whether setContextClassLoader turns out to be necessary
+                // or not, we fail fast if permission is not available.
+                sm.checkPermission(new RuntimePermission("setContextClassLoader"));
+            }
+            this.task = task;
+            this.acc = AccessController.getContext();
+            this.ccl = Thread.currentThread().getContextClassLoader();
+        }
+
+        public T call() throws Exception {
+            try {
+                return AccessController.doPrivileged(
+                    new PrivilegedExceptionAction<T>() {
+                        public T run() throws Exception {
+                            Thread t = Thread.currentThread();
+                            ClassLoader cl = t.getContextClassLoader();
+                            if (ccl == cl) {
+                                return task.call();
+                            } else {
+                                t.setContextClassLoader(ccl);
+                                try {
+                                    return task.call();
+                                } finally {
+                                    t.setContextClassLoader(cl);
+                                }
+                            }
+                        }
+                    }, acc);
+            } catch (PrivilegedActionException e) {
+                throw e.getException();
+            }
+        }
+    }
+
+    /**
+     * The default thread factory.
+     */
+    private static class DefaultThreadFactory implements ThreadFactory {
+        private static final AtomicInteger poolNumber = new AtomicInteger(1);
+        private final ThreadGroup group;
+        private final AtomicInteger threadNumber = new AtomicInteger(1);
+        private final String namePrefix;
+
+        DefaultThreadFactory() {
+            SecurityManager s = System.getSecurityManager();
+            group = (s != null) ? s.getThreadGroup() :
+                                  Thread.currentThread().getThreadGroup();
+            namePrefix = "pool-" +
+                          poolNumber.getAndIncrement() +
+                         "-thread-";
+        }
+
+        public Thread newThread(Runnable r) {
+            Thread t = new Thread(group, r,
+                                  namePrefix + threadNumber.getAndIncrement(),
+                                  0);
+            if (t.isDaemon())
+                t.setDaemon(false);
+            if (t.getPriority() != Thread.NORM_PRIORITY)
+                t.setPriority(Thread.NORM_PRIORITY);
+            return t;
+        }
+    }
+
+    /**
+     * Thread factory capturing access control context and class loader.
+     */
+    private static class PrivilegedThreadFactory extends DefaultThreadFactory {
+        final AccessControlContext acc;
+        final ClassLoader ccl;
+
+        PrivilegedThreadFactory() {
+            super();
+            SecurityManager sm = System.getSecurityManager();
+            if (sm != null) {
+                // Calls to getContextClassLoader from this class
+                // never trigger a security check, but we check
+                // whether our callers have this permission anyways.
+                sm.checkPermission(SecurityConstants.GET_CLASSLOADER_PERMISSION);
+
+                // Fail fast
+                sm.checkPermission(new RuntimePermission("setContextClassLoader"));
+            }
+            this.acc = AccessController.getContext();
+            this.ccl = Thread.currentThread().getContextClassLoader();
+        }
+
+        public Thread newThread(final Runnable r) {
+            return super.newThread(new Runnable() {
+                public void run() {
+                    AccessController.doPrivileged(new PrivilegedAction<>() {
+                        public Void run() {
+                            Thread.currentThread().setContextClassLoader(ccl);
+                            r.run();
+                            return null;
+                        }
+                    }, acc);
+                }
+            });
+        }
+    }
+
+    /**
+     * A wrapper class that exposes only the ExecutorService methods
+     * of an ExecutorService implementation.
+     */
+    private static class DelegatedExecutorService
+            extends AbstractExecutorService {
+        private final ExecutorService e;
+        DelegatedExecutorService(ExecutorService executor) { e = executor; }
+        public void execute(Runnable command) { e.execute(command); }
+        public void shutdown() { e.shutdown(); }
+        public List<Runnable> shutdownNow() { return e.shutdownNow(); }
+        public boolean isShutdown() { return e.isShutdown(); }
+        public boolean isTerminated() { return e.isTerminated(); }
+        public boolean awaitTermination(long timeout, TimeUnit unit)
+            throws InterruptedException {
+            return e.awaitTermination(timeout, unit);
+        }
+        public Future<?> submit(Runnable task) {
+            return e.submit(task);
+        }
+        public <T> Future<T> submit(Callable<T> task) {
+            return e.submit(task);
+        }
+        public <T> Future<T> submit(Runnable task, T result) {
+            return e.submit(task, result);
+        }
+        public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks)
+            throws InterruptedException {
+            return e.invokeAll(tasks);
+        }
+        public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks,
+                                             long timeout, TimeUnit unit)
+            throws InterruptedException {
+            return e.invokeAll(tasks, timeout, unit);
+        }
+        public <T> T invokeAny(Collection<? extends Callable<T>> tasks)
+            throws InterruptedException, ExecutionException {
+            return e.invokeAny(tasks);
+        }
+        public <T> T invokeAny(Collection<? extends Callable<T>> tasks,
+                               long timeout, TimeUnit unit)
+            throws InterruptedException, ExecutionException, TimeoutException {
+            return e.invokeAny(tasks, timeout, unit);
+        }
+    }
+
+    private static class FinalizableDelegatedExecutorService
+            extends DelegatedExecutorService {
+        FinalizableDelegatedExecutorService(ExecutorService executor) {
+            super(executor);
+        }
+        @SuppressWarnings("deprecation")
+        protected void finalize() {
+            super.shutdown();
+        }
+    }
+
+    /**
+     * A wrapper class that exposes only the ScheduledExecutorService
+     * methods of a ScheduledExecutorService implementation.
+     */
+    private static class DelegatedScheduledExecutorService
+            extends DelegatedExecutorService
+            implements ScheduledExecutorService {
+        private final ScheduledExecutorService e;
+        DelegatedScheduledExecutorService(ScheduledExecutorService executor) {
+            super(executor);
+            e = executor;
+        }
+        public ScheduledFuture<?> schedule(Runnable command, long delay, TimeUnit unit) {
+            return e.schedule(command, delay, unit);
+        }
+        public <V> ScheduledFuture<V> schedule(Callable<V> callable, long delay, TimeUnit unit) {
+            return e.schedule(callable, delay, unit);
+        }
+        public ScheduledFuture<?> scheduleAtFixedRate(Runnable command, long initialDelay, long period, TimeUnit unit) {
+            return e.scheduleAtFixedRate(command, initialDelay, period, unit);
+        }
+        public ScheduledFuture<?> scheduleWithFixedDelay(Runnable command, long initialDelay, long delay, TimeUnit unit) {
+            return e.scheduleWithFixedDelay(command, initialDelay, delay, unit);
+        }
+    }
+
+    /** Cannot instantiate. */
+    private Executors() {}
+}

src/java.base/share/classes/java/util/concurrent/Flow.java

@@ -0,0 +1,319 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent;
+
+/**
+ * Interrelated interfaces and static methods for establishing
+ * flow-controlled components in which {@link Publisher Publishers}
+ * produce items consumed by one or more {@link Subscriber
+ * Subscribers}, each managed by a {@link Subscription
+ * Subscription}.
+ *
+ * <p>These interfaces correspond to the <a
+ * href="http://www.reactive-streams.org/"> reactive-streams</a>
+ * specification.  They apply in both concurrent and distributed
+ * asynchronous settings: All (seven) methods are defined in {@code
+ * void} "one-way" message style. Communication relies on a simple form
+ * of flow control (method {@link Subscription#request}) that can be
+ * used to avoid resource management problems that may otherwise occur
+ * in "push" based systems.
+ *
+ * <p><b>Examples.</b> A {@link Publisher} usually defines its own
+ * {@link Subscription} implementation; constructing one in method
+ * {@code subscribe} and issuing it to the calling {@link
+ * Subscriber}. It publishes items to the subscriber asynchronously,
+ * normally using an {@link Executor}.  For example, here is a very
+ * simple publisher that only issues (when requested) a single {@code
+ * TRUE} item to a single subscriber.  Because the subscriber receives
+ * only a single item, this class does not use buffering and ordering
+ * control required in most implementations (for example {@link
+ * SubmissionPublisher}).
+ *
+ * <pre> {@code
+ * class OneShotPublisher implements Publisher<Boolean> {
+ *   private final ExecutorService executor = ForkJoinPool.commonPool(); // daemon-based
+ *   private boolean subscribed; // true after first subscribe
+ *   public synchronized void subscribe(Subscriber<? super Boolean> subscriber) {
+ *     if (subscribed)
+ *       subscriber.onError(new IllegalStateException()); // only one allowed
+ *     else {
+ *       subscribed = true;
+ *       subscriber.onSubscribe(new OneShotSubscription(subscriber, executor));
+ *     }
+ *   }
+ *   static class OneShotSubscription implements Subscription {
+ *     private final Subscriber<? super Boolean> subscriber;
+ *     private final ExecutorService executor;
+ *     private Future<?> future; // to allow cancellation
+ *     private boolean completed;
+ *     OneShotSubscription(Subscriber<? super Boolean> subscriber,
+ *                         ExecutorService executor) {
+ *       this.subscriber = subscriber;
+ *       this.executor = executor;
+ *     }
+ *     public synchronized void request(long n) {
+ *       if (!completed) {
+ *         completed = true;
+ *         if (n <= 0) {
+ *           IllegalArgumentException ex = new IllegalArgumentException();
+ *           executor.execute(() -> subscriber.onError(ex));
+ *         } else {
+ *           future = executor.submit(() -> {
+ *             subscriber.onNext(Boolean.TRUE);
+ *             subscriber.onComplete();
+ *           });
+ *         }
+ *       }
+ *     }
+ *     public synchronized void cancel() {
+ *       completed = true;
+ *       if (future != null) future.cancel(false);
+ *     }
+ *   }
+ * }}</pre>
+ *
+ * <p>A {@link Subscriber} arranges that items be requested and
+ * processed.  Items (invocations of {@link Subscriber#onNext}) are
+ * not issued unless requested, but multiple items may be requested.
+ * Many Subscriber implementations can arrange this in the style of
+ * the following example, where a buffer size of 1 single-steps, and
+ * larger sizes usually allow for more efficient overlapped processing
+ * with less communication; for example with a value of 64, this keeps
+ * total outstanding requests between 32 and 64.
+ * Because Subscriber method invocations for a given {@link
+ * Subscription} are strictly ordered, there is no need for these
+ * methods to use locks or volatiles unless a Subscriber maintains
+ * multiple Subscriptions (in which case it is better to instead
+ * define multiple Subscribers, each with its own Subscription).
+ *
+ * <pre> {@code
+ * class SampleSubscriber<T> implements Subscriber<T> {
+ *   final Consumer<? super T> consumer;
+ *   Subscription subscription;
+ *   final long bufferSize;
+ *   long count;
+ *   SampleSubscriber(long bufferSize, Consumer<? super T> consumer) {
+ *     this.bufferSize = bufferSize;
+ *     this.consumer = consumer;
+ *   }
+ *   public void onSubscribe(Subscription subscription) {
+ *     long initialRequestSize = bufferSize;
+ *     count = bufferSize - bufferSize / 2; // re-request when half consumed
+ *     (this.subscription = subscription).request(initialRequestSize);
+ *   }
+ *   public void onNext(T item) {
+ *     if (--count <= 0)
+ *       subscription.request(count = bufferSize - bufferSize / 2);
+ *     consumer.accept(item);
+ *   }
+ *   public void onError(Throwable ex) { ex.printStackTrace(); }
+ *   public void onComplete() {}
+ * }}</pre>
+ *
+ * <p>The default value of {@link #defaultBufferSize} may provide a
+ * useful starting point for choosing request sizes and capacities in
+ * Flow components based on expected rates, resources, and usages.
+ * Or, when flow control is never needed, a subscriber may initially
+ * request an effectively unbounded number of items, as in:
+ *
+ * <pre> {@code
+ * class UnboundedSubscriber<T> implements Subscriber<T> {
+ *   public void onSubscribe(Subscription subscription) {
+ *     subscription.request(Long.MAX_VALUE); // effectively unbounded
+ *   }
+ *   public void onNext(T item) { use(item); }
+ *   public void onError(Throwable ex) { ex.printStackTrace(); }
+ *   public void onComplete() {}
+ *   void use(T item) { ... }
+ * }}</pre>
+ *
+ * @author Doug Lea
+ * @since 9
+ */
+public final class Flow {
+
+    private Flow() {} // uninstantiable
+
+    /**
+     * A producer of items (and related control messages) received by
+     * Subscribers.  Each current {@link Subscriber} receives the same
+     * items (via method {@code onNext}) in the same order, unless
+     * drops or errors are encountered. If a Publisher encounters an
+     * error that does not allow items to be issued to a Subscriber,
+     * that Subscriber receives {@code onError}, and then receives no
+     * further messages.  Otherwise, when it is known that no further
+     * messages will be issued to it, a subscriber receives {@code
+     * onComplete}.  Publishers ensure that Subscriber method
+     * invocations for each subscription are strictly ordered in <a
+     * href="package-summary.html#MemoryVisibility"><i>happens-before</i></a>
+     * order.
+     *
+     * <p>Publishers may vary in policy about whether drops (failures
+     * to issue an item because of resource limitations) are treated
+     * as unrecoverable errors.  Publishers may also vary about
+     * whether Subscribers receive items that were produced or
+     * available before they subscribed.
+     *
+     * @param <T> the published item type
+     */
+    @FunctionalInterface
+    public static interface Publisher<T> {
+        /**
+         * Adds the given Subscriber if possible.  If already
+         * subscribed, or the attempt to subscribe fails due to policy
+         * violations or errors, the Subscriber's {@code onError}
+         * method is invoked with an {@link IllegalStateException}.
+         * Otherwise, the Subscriber's {@code onSubscribe} method is
+         * invoked with a new {@link Subscription}.  Subscribers may
+         * enable receiving items by invoking the {@code request}
+         * method of this Subscription, and may unsubscribe by
+         * invoking its {@code cancel} method.
+         *
+         * @param subscriber the subscriber
+         * @throws NullPointerException if subscriber is null
+         */
+        public void subscribe(Subscriber<? super T> subscriber);
+    }
+
+    /**
+     * A receiver of messages.  The methods in this interface are
+     * invoked in strict sequential order for each {@link
+     * Subscription}.
+     *
+     * @param <T> the subscribed item type
+     */
+    public static interface Subscriber<T> {
+        /**
+         * Method invoked prior to invoking any other Subscriber
+         * methods for the given Subscription. If this method throws
+         * an exception, resulting behavior is not guaranteed, but may
+         * cause the Subscription not to be established or to be cancelled.
+         *
+         * <p>Typically, implementations of this method invoke {@code
+         * subscription.request} to enable receiving items.
+         *
+         * @param subscription a new subscription
+         */
+        public void onSubscribe(Subscription subscription);
+
+        /**
+         * Method invoked with a Subscription's next item.  If this
+         * method throws an exception, resulting behavior is not
+         * guaranteed, but may cause the Subscription to be cancelled.
+         *
+         * @param item the item
+         */
+        public void onNext(T item);
+
+        /**
+         * Method invoked upon an unrecoverable error encountered by a
+         * Publisher or Subscription, after which no other Subscriber
+         * methods are invoked by the Subscription.  If this method
+         * itself throws an exception, resulting behavior is
+         * undefined.
+         *
+         * @param throwable the exception
+         */
+        public void onError(Throwable throwable);
+
+        /**
+         * Method invoked when it is known that no additional
+         * Subscriber method invocations will occur for a Subscription
+         * that is not already terminated by error, after which no
+         * other Subscriber methods are invoked by the Subscription.
+         * If this method throws an exception, resulting behavior is
+         * undefined.
+         */
+        public void onComplete();
+    }
+
+    /**
+     * Message control linking a {@link Publisher} and {@link
+     * Subscriber}.  Subscribers receive items only when requested,
+     * and may cancel at any time. The methods in this interface are
+     * intended to be invoked only by their Subscribers; usages in
+     * other contexts have undefined effects.
+     */
+    public static interface Subscription {
+        /**
+         * Adds the given number {@code n} of items to the current
+         * unfulfilled demand for this subscription.  If {@code n} is
+         * less than or equal to zero, the Subscriber will receive an
+         * {@code onError} signal with an {@link
+         * IllegalArgumentException} argument.  Otherwise, the
+         * Subscriber will receive up to {@code n} additional {@code
+         * onNext} invocations (or fewer if terminated).
+         *
+         * @param n the increment of demand; a value of {@code
+         * Long.MAX_VALUE} may be considered as effectively unbounded
+         */
+        public void request(long n);
+
+        /**
+         * Causes the Subscriber to (eventually) stop receiving
+         * messages.  Implementation is best-effort -- additional
+         * messages may be received after invoking this method.
+         * A cancelled subscription need not ever receive an
+         * {@code onComplete} or {@code onError} signal.
+         */
+        public void cancel();
+    }
+
+    /**
+     * A component that acts as both a Subscriber and Publisher.
+     *
+     * @param <T> the subscribed item type
+     * @param <R> the published item type
+     */
+    public static interface Processor<T,R> extends Subscriber<T>, Publisher<R> {
+    }
+
+    static final int DEFAULT_BUFFER_SIZE = 256;
+
+    /**
+     * Returns a default value for Publisher or Subscriber buffering,
+     * that may be used in the absence of other constraints.
+     *
+     * @implNote
+     * The current value returned is 256.
+     *
+     * @return the buffer size value
+     */
+    public static int defaultBufferSize() {
+        return DEFAULT_BUFFER_SIZE;
+    }
+
+}

src/java.base/share/classes/java/util/concurrent/ForkJoinWorkerThread.java

@@ -0,0 +1,242 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent;
+
+import java.security.AccessControlContext;
+import java.security.AccessController;
+import java.security.PrivilegedAction;
+import java.security.ProtectionDomain;
+
+/**
+ * A thread managed by a {@link ForkJoinPool}, which executes
+ * {@link ForkJoinTask}s.
+ * This class is subclassable solely for the sake of adding
+ * functionality -- there are no overridable methods dealing with
+ * scheduling or execution.  However, you can override initialization
+ * and termination methods surrounding the main task processing loop.
+ * If you do create such a subclass, you will also need to supply a
+ * custom {@link ForkJoinPool.ForkJoinWorkerThreadFactory} to
+ * {@linkplain ForkJoinPool#ForkJoinPool(int, ForkJoinWorkerThreadFactory,
+ * UncaughtExceptionHandler, boolean, int, int, int, Predicate, long, TimeUnit)
+ * use it} in a {@code ForkJoinPool}.
+ *
+ * @since 1.7
+ * @author Doug Lea
+ */
+public class ForkJoinWorkerThread extends Thread {
+    /*
+     * ForkJoinWorkerThreads are managed by ForkJoinPools and perform
+     * ForkJoinTasks. For explanation, see the internal documentation
+     * of class ForkJoinPool.
+     *
+     * This class just maintains links to its pool and WorkQueue.  The
+     * pool field is set immediately upon construction, but the
+     * workQueue field is not set until a call to registerWorker
+     * completes. This leads to a visibility race, that is tolerated
+     * by requiring that the workQueue field is only accessed by the
+     * owning thread.
+     *
+     * Support for (non-public) subclass InnocuousForkJoinWorkerThread
+     * requires that we break quite a lot of encapsulation (via helper
+     * methods in ThreadLocalRandom) both here and in the subclass to
+     * access and set Thread fields.
+     */
+
+    final ForkJoinPool pool;                // the pool this thread works in
+    final ForkJoinPool.WorkQueue workQueue; // work-stealing mechanics
+
+    /**
+     * Creates a ForkJoinWorkerThread operating in the given pool.
+     *
+     * @param pool the pool this thread works in
+     * @throws NullPointerException if pool is null
+     */
+    protected ForkJoinWorkerThread(ForkJoinPool pool) {
+        // Use a placeholder until a useful name can be set in registerWorker
+        super("aForkJoinWorkerThread");
+        this.pool = pool;
+        this.workQueue = pool.registerWorker(this);
+    }
+
+    /**
+     * Version for use by the default pool.  Supports setting the
+     * context class loader.  This is a separate constructor to avoid
+     * affecting the protected constructor.
+     */
+    ForkJoinWorkerThread(ForkJoinPool pool, ClassLoader ccl) {
+        super("aForkJoinWorkerThread");
+        super.setContextClassLoader(ccl);
+        this.pool = pool;
+        this.workQueue = pool.registerWorker(this);
+    }
+
+    /**
+     * Version for InnocuousForkJoinWorkerThread.
+     */
+    ForkJoinWorkerThread(ForkJoinPool pool,
+                         ClassLoader ccl,
+                         ThreadGroup threadGroup,
+                         AccessControlContext acc) {
+        super(threadGroup, null, "aForkJoinWorkerThread");
+        super.setContextClassLoader(ccl);
+        ThreadLocalRandom.setInheritedAccessControlContext(this, acc);
+        ThreadLocalRandom.eraseThreadLocals(this); // clear before registering
+        this.pool = pool;
+        this.workQueue = pool.registerWorker(this);
+    }
+
+    /**
+     * Returns the pool hosting this thread.
+     *
+     * @return the pool
+     */
+    public ForkJoinPool getPool() {
+        return pool;
+    }
+
+    /**
+     * Returns the unique index number of this thread in its pool.
+     * The returned value ranges from zero to the maximum number of
+     * threads (minus one) that may exist in the pool, and does not
+     * change during the lifetime of the thread.  This method may be
+     * useful for applications that track status or collect results
+     * per-worker-thread rather than per-task.
+     *
+     * @return the index number
+     */
+    public int getPoolIndex() {
+        return workQueue.getPoolIndex();
+    }
+
+    /**
+     * Initializes internal state after construction but before
+     * processing any tasks. If you override this method, you must
+     * invoke {@code super.onStart()} at the beginning of the method.
+     * Initialization requires care: Most fields must have legal
+     * default values, to ensure that attempted accesses from other
+     * threads work correctly even before this thread starts
+     * processing tasks.
+     */
+    protected void onStart() {
+    }
+
+    /**
+     * Performs cleanup associated with termination of this worker
+     * thread.  If you override this method, you must invoke
+     * {@code super.onTermination} at the end of the overridden method.
+     *
+     * @param exception the exception causing this thread to abort due
+     * to an unrecoverable error, or {@code null} if completed normally
+     */
+    protected void onTermination(Throwable exception) {
+    }
+
+    /**
+     * This method is required to be public, but should never be
+     * called explicitly. It performs the main run loop to execute
+     * {@link ForkJoinTask}s.
+     */
+    public void run() {
+        if (workQueue.array == null) { // only run once
+            Throwable exception = null;
+            try {
+                onStart();
+                pool.runWorker(workQueue);
+            } catch (Throwable ex) {
+                exception = ex;
+            } finally {
+                try {
+                    onTermination(exception);
+                } catch (Throwable ex) {
+                    if (exception == null)
+                        exception = ex;
+                } finally {
+                    pool.deregisterWorker(this, exception);
+                }
+            }
+        }
+    }
+
+    /**
+     * Non-public hook method for InnocuousForkJoinWorkerThread.
+     */
+    void afterTopLevelExec() {
+    }
+
+    /**
+     * A worker thread that has no permissions, is not a member of any
+     * user-defined ThreadGroup, uses the system class loader as
+     * thread context class loader, and erases all ThreadLocals after
+     * running each top-level task.
+     */
+    static final class InnocuousForkJoinWorkerThread extends ForkJoinWorkerThread {
+        /** The ThreadGroup for all InnocuousForkJoinWorkerThreads */
+        private static final ThreadGroup innocuousThreadGroup =
+            AccessController.doPrivileged(new PrivilegedAction<>() {
+                public ThreadGroup run() {
+                    ThreadGroup group = Thread.currentThread().getThreadGroup();
+                    for (ThreadGroup p; (p = group.getParent()) != null; )
+                        group = p;
+                    return new ThreadGroup(
+                        group, "InnocuousForkJoinWorkerThreadGroup");
+                }});
+
+        /** An AccessControlContext supporting no privileges */
+        private static final AccessControlContext INNOCUOUS_ACC =
+            new AccessControlContext(
+                new ProtectionDomain[] { new ProtectionDomain(null, null) });
+
+        InnocuousForkJoinWorkerThread(ForkJoinPool pool) {
+            super(pool,
+                  ClassLoader.getSystemClassLoader(),
+                  innocuousThreadGroup,
+                  INNOCUOUS_ACC);
+        }
+
+        @Override // to erase ThreadLocals
+        void afterTopLevelExec() {
+            ThreadLocalRandom.eraseThreadLocals(this);
+        }
+
+        @Override // to silently fail
+        public void setUncaughtExceptionHandler(UncaughtExceptionHandler x) { }
+
+        @Override // paranoically
+        public void setContextClassLoader(ClassLoader cl) {
+            throw new SecurityException("setContextClassLoader");
+        }
+    }
+}

src/java.base/share/classes/java/util/concurrent/Future.java

@@ -0,0 +1,161 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent;
+
+/**
+ * A {@code Future} represents the result of an asynchronous
+ * computation.  Methods are provided to check if the computation is
+ * complete, to wait for its completion, and to retrieve the result of
+ * the computation.  The result can only be retrieved using method
+ * {@code get} when the computation has completed, blocking if
+ * necessary until it is ready.  Cancellation is performed by the
+ * {@code cancel} method.  Additional methods are provided to
+ * determine if the task completed normally or was cancelled. Once a
+ * computation has completed, the computation cannot be cancelled.
+ * If you would like to use a {@code Future} for the sake
+ * of cancellability but not provide a usable result, you can
+ * declare types of the form {@code Future<?>} and
+ * return {@code null} as a result of the underlying task.
+ *
+ * <p><b>Sample Usage</b> (Note that the following classes are all
+ * made-up.)
+ *
+ * <pre> {@code
+ * interface ArchiveSearcher { String search(String target); }
+ * class App {
+ *   ExecutorService executor = ...
+ *   ArchiveSearcher searcher = ...
+ *   void showSearch(String target) throws InterruptedException {
+ *     Callable<String> task = () -> searcher.search(target);
+ *     Future<String> future = executor.submit(task);
+ *     displayOtherThings(); // do other things while searching
+ *     try {
+ *       displayText(future.get()); // use future
+ *     } catch (ExecutionException ex) { cleanup(); return; }
+ *   }
+ * }}</pre>
+ *
+ * The {@link FutureTask} class is an implementation of {@code Future} that
+ * implements {@code Runnable}, and so may be executed by an {@code Executor}.
+ * For example, the above construction with {@code submit} could be replaced by:
+ * <pre> {@code
+ * FutureTask<String> future = new FutureTask<>(task);
+ * executor.execute(future);}</pre>
+ *
+ * <p>Memory consistency effects: Actions taken by the asynchronous computation
+ * <a href="package-summary.html#MemoryVisibility"> <i>happen-before</i></a>
+ * actions following the corresponding {@code Future.get()} in another thread.
+ *
+ * @see FutureTask
+ * @see Executor
+ * @since 1.5
+ * @author Doug Lea
+ * @param <V> The result type returned by this Future's {@code get} method
+ */
+public interface Future<V> {
+
+    /**
+     * Attempts to cancel execution of this task.  This attempt will
+     * fail if the task has already completed, has already been cancelled,
+     * or could not be cancelled for some other reason. If successful,
+     * and this task has not started when {@code cancel} is called,
+     * this task should never run.  If the task has already started,
+     * then the {@code mayInterruptIfRunning} parameter determines
+     * whether the thread executing this task should be interrupted in
+     * an attempt to stop the task.
+     *
+     * <p>After this method returns, subsequent calls to {@link #isDone} will
+     * always return {@code true}.  Subsequent calls to {@link #isCancelled}
+     * will always return {@code true} if this method returned {@code true}.
+     *
+     * @param mayInterruptIfRunning {@code true} if the thread executing this
+     * task should be interrupted; otherwise, in-progress tasks are allowed
+     * to complete
+     * @return {@code false} if the task could not be cancelled,
+     * typically because it has already completed normally;
+     * {@code true} otherwise
+     */
+    boolean cancel(boolean mayInterruptIfRunning);
+
+    /**
+     * Returns {@code true} if this task was cancelled before it completed
+     * normally.
+     *
+     * @return {@code true} if this task was cancelled before it completed
+     */
+    boolean isCancelled();
+
+    /**
+     * Returns {@code true} if this task completed.
+     *
+     * Completion may be due to normal termination, an exception, or
+     * cancellation -- in all of these cases, this method will return
+     * {@code true}.
+     *
+     * @return {@code true} if this task completed
+     */
+    boolean isDone();
+
+    /**
+     * Waits if necessary for the computation to complete, and then
+     * retrieves its result.
+     *
+     * @return the computed result
+     * @throws CancellationException if the computation was cancelled
+     * @throws ExecutionException if the computation threw an
+     * exception
+     * @throws InterruptedException if the current thread was interrupted
+     * while waiting
+     */
+    V get() throws InterruptedException, ExecutionException;
+
+    /**
+     * Waits if necessary for at most the given time for the computation
+     * to complete, and then retrieves its result, if available.
+     *
+     * @param timeout the maximum time to wait
+     * @param unit the time unit of the timeout argument
+     * @return the computed result
+     * @throws CancellationException if the computation was cancelled
+     * @throws ExecutionException if the computation threw an
+     * exception
+     * @throws InterruptedException if the current thread was interrupted
+     * while waiting
+     * @throws TimeoutException if the wait timed out
+     */
+    V get(long timeout, TimeUnit unit)
+        throws InterruptedException, ExecutionException, TimeoutException;
+}

src/java.base/share/classes/java/util/concurrent/FutureTask.java

@@ -0,0 +1,502 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent;
+
+import java.lang.invoke.MethodHandles;
+import java.lang.invoke.VarHandle;
+import java.util.concurrent.locks.LockSupport;
+
+/**
+ * A cancellable asynchronous computation.  This class provides a base
+ * implementation of {@link Future}, with methods to start and cancel
+ * a computation, query to see if the computation is complete, and
+ * retrieve the result of the computation.  The result can only be
+ * retrieved when the computation has completed; the {@code get}
+ * methods will block if the computation has not yet completed.  Once
+ * the computation has completed, the computation cannot be restarted
+ * or cancelled (unless the computation is invoked using
+ * {@link #runAndReset}).
+ *
+ * <p>A {@code FutureTask} can be used to wrap a {@link Callable} or
+ * {@link Runnable} object.  Because {@code FutureTask} implements
+ * {@code Runnable}, a {@code FutureTask} can be submitted to an
+ * {@link Executor} for execution.
+ *
+ * <p>In addition to serving as a standalone class, this class provides
+ * {@code protected} functionality that may be useful when creating
+ * customized task classes.
+ *
+ * @since 1.5
+ * @author Doug Lea
+ * @param <V> The result type returned by this FutureTask's {@code get} methods
+ */
+public class FutureTask<V> implements RunnableFuture<V> {
+    /*
+     * Revision notes: This differs from previous versions of this
+     * class that relied on AbstractQueuedSynchronizer, mainly to
+     * avoid surprising users about retaining interrupt status during
+     * cancellation races. Sync control in the current design relies
+     * on a "state" field updated via CAS to track completion, along
+     * with a simple Treiber stack to hold waiting threads.
+     */
+
+    /**
+     * The run state of this task, initially NEW.  The run state
+     * transitions to a terminal state only in methods set,
+     * setException, and cancel.  During completion, state may take on
+     * transient values of COMPLETING (while outcome is being set) or
+     * INTERRUPTING (only while interrupting the runner to satisfy a
+     * cancel(true)). Transitions from these intermediate to final
+     * states use cheaper ordered/lazy writes because values are unique
+     * and cannot be further modified.
+     *
+     * Possible state transitions:
+     * NEW -> COMPLETING -> NORMAL
+     * NEW -> COMPLETING -> EXCEPTIONAL
+     * NEW -> CANCELLED
+     * NEW -> INTERRUPTING -> INTERRUPTED
+     */
+    private volatile int state;
+    private static final int NEW          = 0;
+    private static final int COMPLETING   = 1;
+    private static final int NORMAL       = 2;
+    private static final int EXCEPTIONAL  = 3;
+    private static final int CANCELLED    = 4;
+    private static final int INTERRUPTING = 5;
+    private static final int INTERRUPTED  = 6;
+
+    /** The underlying callable; nulled out after running */
+    private Callable<V> callable;
+    /** The result to return or exception to throw from get() */
+    private Object outcome; // non-volatile, protected by state reads/writes
+    /** The thread running the callable; CASed during run() */
+    private volatile Thread runner;
+    /** Treiber stack of waiting threads */
+    private volatile WaitNode waiters;
+
+    /**
+     * Returns result or throws exception for completed task.
+     *
+     * @param s completed state value
+     */
+    @SuppressWarnings("unchecked")
+    private V report(int s) throws ExecutionException {
+        Object x = outcome;
+        if (s == NORMAL)
+            return (V)x;
+        if (s >= CANCELLED)
+            throw new CancellationException();
+        throw new ExecutionException((Throwable)x);
+    }
+
+    /**
+     * Creates a {@code FutureTask} that will, upon running, execute the
+     * given {@code Callable}.
+     *
+     * @param  callable the callable task
+     * @throws NullPointerException if the callable is null
+     */
+    public FutureTask(Callable<V> callable) {
+        if (callable == null)
+            throw new NullPointerException();
+        this.callable = callable;
+        this.state = NEW;       // ensure visibility of callable
+    }
+
+    /**
+     * Creates a {@code FutureTask} that will, upon running, execute the
+     * given {@code Runnable}, and arrange that {@code get} will return the
+     * given result on successful completion.
+     *
+     * @param runnable the runnable task
+     * @param result the result to return on successful completion. If
+     * you don't need a particular result, consider using
+     * constructions of the form:
+     * {@code Future<?> f = new FutureTask<Void>(runnable, null)}
+     * @throws NullPointerException if the runnable is null
+     */
+    public FutureTask(Runnable runnable, V result) {
+        this.callable = Executors.callable(runnable, result);
+        this.state = NEW;       // ensure visibility of callable
+    }
+
+    public boolean isCancelled() {
+        return state >= CANCELLED;
+    }
+
+    public boolean isDone() {
+        return state != NEW;
+    }
+
+    public boolean cancel(boolean mayInterruptIfRunning) {
+        if (!(state == NEW && STATE.compareAndSet
+              (this, NEW, mayInterruptIfRunning ? INTERRUPTING : CANCELLED)))
+            return false;
+        try {    // in case call to interrupt throws exception
+            if (mayInterruptIfRunning) {
+                try {
+                    Thread t = runner;
+                    if (t != null)
+                        t.interrupt();
+                } finally { // final state
+                    STATE.setRelease(this, INTERRUPTED);
+                }
+            }
+        } finally {
+            finishCompletion();
+        }
+        return true;
+    }
+
+    /**
+     * @throws CancellationException {@inheritDoc}
+     */
+    public V get() throws InterruptedException, ExecutionException {
+        int s = state;
+        if (s <= COMPLETING)
+            s = awaitDone(false, 0L);
+        return report(s);
+    }
+
+    /**
+     * @throws CancellationException {@inheritDoc}
+     */
+    public V get(long timeout, TimeUnit unit)
+        throws InterruptedException, ExecutionException, TimeoutException {
+        if (unit == null)
+            throw new NullPointerException();
+        int s = state;
+        if (s <= COMPLETING &&
+            (s = awaitDone(true, unit.toNanos(timeout))) <= COMPLETING)
+            throw new TimeoutException();
+        return report(s);
+    }
+
+    /**
+     * Protected method invoked when this task transitions to state
+     * {@code isDone} (whether normally or via cancellation). The
+     * default implementation does nothing.  Subclasses may override
+     * this method to invoke completion callbacks or perform
+     * bookkeeping. Note that you can query status inside the
+     * implementation of this method to determine whether this task
+     * has been cancelled.
+     */
+    protected void done() { }
+
+    /**
+     * Sets the result of this future to the given value unless
+     * this future has already been set or has been cancelled.
+     *
+     * <p>This method is invoked internally by the {@link #run} method
+     * upon successful completion of the computation.
+     *
+     * @param v the value
+     */
+    protected void set(V v) {
+        if (STATE.compareAndSet(this, NEW, COMPLETING)) {
+            outcome = v;
+            STATE.setRelease(this, NORMAL); // final state
+            finishCompletion();
+        }
+    }
+
+    /**
+     * Causes this future to report an {@link ExecutionException}
+     * with the given throwable as its cause, unless this future has
+     * already been set or has been cancelled.
+     *
+     * <p>This method is invoked internally by the {@link #run} method
+     * upon failure of the computation.
+     *
+     * @param t the cause of failure
+     */
+    protected void setException(Throwable t) {
+        if (STATE.compareAndSet(this, NEW, COMPLETING)) {
+            outcome = t;
+            STATE.setRelease(this, EXCEPTIONAL); // final state
+            finishCompletion();
+        }
+    }
+
+    public void run() {
+        if (state != NEW ||
+            !RUNNER.compareAndSet(this, null, Thread.currentThread()))
+            return;
+        try {
+            Callable<V> c = callable;
+            if (c != null && state == NEW) {
+                V result;
+                boolean ran;
+                try {
+                    result = c.call();
+                    ran = true;
+                } catch (Throwable ex) {
+                    result = null;
+                    ran = false;
+                    setException(ex);
+                }
+                if (ran)
+                    set(result);
+            }
+        } finally {
+            // runner must be non-null until state is settled to
+            // prevent concurrent calls to run()
+            runner = null;
+            // state must be re-read after nulling runner to prevent
+            // leaked interrupts
+            int s = state;
+            if (s >= INTERRUPTING)
+                handlePossibleCancellationInterrupt(s);
+        }
+    }
+
+    /**
+     * Executes the computation without setting its result, and then
+     * resets this future to initial state, failing to do so if the
+     * computation encounters an exception or is cancelled.  This is
+     * designed for use with tasks that intrinsically execute more
+     * than once.
+     *
+     * @return {@code true} if successfully run and reset
+     */
+    protected boolean runAndReset() {
+        if (state != NEW ||
+            !RUNNER.compareAndSet(this, null, Thread.currentThread()))
+            return false;
+        boolean ran = false;
+        int s = state;
+        try {
+            Callable<V> c = callable;
+            if (c != null && s == NEW) {
+                try {
+                    c.call(); // don't set result
+                    ran = true;
+                } catch (Throwable ex) {
+                    setException(ex);
+                }
+            }
+        } finally {
+            // runner must be non-null until state is settled to
+            // prevent concurrent calls to run()
+            runner = null;
+            // state must be re-read after nulling runner to prevent
+            // leaked interrupts
+            s = state;
+            if (s >= INTERRUPTING)
+                handlePossibleCancellationInterrupt(s);
+        }
+        return ran && s == NEW;
+    }
+
+    /**
+     * Ensures that any interrupt from a possible cancel(true) is only
+     * delivered to a task while in run or runAndReset.
+     */
+    private void handlePossibleCancellationInterrupt(int s) {
+        // It is possible for our interrupter to stall before getting a
+        // chance to interrupt us.  Let's spin-wait patiently.
+        if (s == INTERRUPTING)
+            while (state == INTERRUPTING)
+                Thread.yield(); // wait out pending interrupt
+
+        // assert state == INTERRUPTED;
+
+        // We want to clear any interrupt we may have received from
+        // cancel(true).  However, it is permissible to use interrupts
+        // as an independent mechanism for a task to communicate with
+        // its caller, and there is no way to clear only the
+        // cancellation interrupt.
+        //
+        // Thread.interrupted();
+    }
+
+    /**
+     * Simple linked list nodes to record waiting threads in a Treiber
+     * stack.  See other classes such as Phaser and SynchronousQueue
+     * for more detailed explanation.
+     */
+    static final class WaitNode {
+        volatile Thread thread;
+        volatile WaitNode next;
+        WaitNode() { thread = Thread.currentThread(); }
+    }
+
+    /**
+     * Removes and signals all waiting threads, invokes done(), and
+     * nulls out callable.
+     */
+    private void finishCompletion() {
+        // assert state > COMPLETING;
+        for (WaitNode q; (q = waiters) != null;) {
+            if (WAITERS.weakCompareAndSet(this, q, null)) {
+                for (;;) {
+                    Thread t = q.thread;
+                    if (t != null) {
+                        q.thread = null;
+                        LockSupport.unpark(t);
+                    }
+                    WaitNode next = q.next;
+                    if (next == null)
+                        break;
+                    q.next = null; // unlink to help gc
+                    q = next;
+                }
+                break;
+            }
+        }
+
+        done();
+
+        callable = null;        // to reduce footprint
+    }
+
+    /**
+     * Awaits completion or aborts on interrupt or timeout.
+     *
+     * @param timed true if use timed waits
+     * @param nanos time to wait, if timed
+     * @return state upon completion or at timeout
+     */
+    private int awaitDone(boolean timed, long nanos)
+        throws InterruptedException {
+        // The code below is very delicate, to achieve these goals:
+        // - call nanoTime exactly once for each call to park
+        // - if nanos <= 0L, return promptly without allocation or nanoTime
+        // - if nanos == Long.MIN_VALUE, don't underflow
+        // - if nanos == Long.MAX_VALUE, and nanoTime is non-monotonic
+        //   and we suffer a spurious wakeup, we will do no worse than
+        //   to park-spin for a while
+        long startTime = 0L;    // Special value 0L means not yet parked
+        WaitNode q = null;
+        boolean queued = false;
+        for (;;) {
+            int s = state;
+            if (s > COMPLETING) {
+                if (q != null)
+                    q.thread = null;
+                return s;
+            }
+            else if (s == COMPLETING)
+                // We may have already promised (via isDone) that we are done
+                // so never return empty-handed or throw InterruptedException
+                Thread.yield();
+            else if (Thread.interrupted()) {
+                removeWaiter(q);
+                throw new InterruptedException();
+            }
+            else if (q == null) {
+                if (timed && nanos <= 0L)
+                    return s;
+                q = new WaitNode();
+            }
+            else if (!queued)
+                queued = WAITERS.weakCompareAndSet(this, q.next = waiters, q);
+            else if (timed) {
+                final long parkNanos;
+                if (startTime == 0L) { // first time
+                    startTime = System.nanoTime();
+                    if (startTime == 0L)
+                        startTime = 1L;
+                    parkNanos = nanos;
+                } else {
+                    long elapsed = System.nanoTime() - startTime;
+                    if (elapsed >= nanos) {
+                        removeWaiter(q);
+                        return state;
+                    }
+                    parkNanos = nanos - elapsed;
+                }
+                // nanoTime may be slow; recheck before parking
+                if (state < COMPLETING)
+                    LockSupport.parkNanos(this, parkNanos);
+            }
+            else
+                LockSupport.park(this);
+        }
+    }
+
+    /**
+     * Tries to unlink a timed-out or interrupted wait node to avoid
+     * accumulating garbage.  Internal nodes are simply unspliced
+     * without CAS since it is harmless if they are traversed anyway
+     * by releasers.  To avoid effects of unsplicing from already
+     * removed nodes, the list is retraversed in case of an apparent
+     * race.  This is slow when there are a lot of nodes, but we don't
+     * expect lists to be long enough to outweigh higher-overhead
+     * schemes.
+     */
+    private void removeWaiter(WaitNode node) {
+        if (node != null) {
+            node.thread = null;
+            retry:
+            for (;;) {          // restart on removeWaiter race
+                for (WaitNode pred = null, q = waiters, s; q != null; q = s) {
+                    s = q.next;
+                    if (q.thread != null)
+                        pred = q;
+                    else if (pred != null) {
+                        pred.next = s;
+                        if (pred.thread == null) // check for race
+                            continue retry;
+                    }
+                    else if (!WAITERS.compareAndSet(this, q, s))
+                        continue retry;
+                }
+                break;
+            }
+        }
+    }
+
+    // VarHandle mechanics
+    private static final VarHandle STATE;
+    private static final VarHandle RUNNER;
+    private static final VarHandle WAITERS;
+    static {
+        try {
+            MethodHandles.Lookup l = MethodHandles.lookup();
+            STATE = l.findVarHandle(FutureTask.class, "state", int.class);
+            RUNNER = l.findVarHandle(FutureTask.class, "runner", Thread.class);
+            WAITERS = l.findVarHandle(FutureTask.class, "waiters", WaitNode.class);
+        } catch (ReflectiveOperationException e) {
+            throw new Error(e);
+        }
+
+        // Reduce the risk of rare disastrous classloading in first call to
+        // LockSupport.park: https://bugs.openjdk.java.net/browse/JDK-8074773
+        Class<?> ensureLoaded = LockSupport.class;
+    }
+
+}

src/java.base/share/classes/java/util/concurrent/Helpers.java

@@ -0,0 +1,118 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Martin Buchholz with assistance from members of JCP
+ * JSR-166 Expert Group and released to the public domain, as
+ * explained at http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent;
+
+import java.util.Collection;
+
+/** Shared implementation code for java.util.concurrent. */
+class Helpers {
+    private Helpers() {}                // non-instantiable
+
+    /**
+     * An implementation of Collection.toString() suitable for classes
+     * with locks.  Instead of holding a lock for the entire duration of
+     * toString(), or acquiring a lock for each call to Iterator.next(),
+     * we hold the lock only during the call to toArray() (less
+     * disruptive to other threads accessing the collection) and follows
+     * the maxim "Never call foreign code while holding a lock".
+     */
+    static String collectionToString(Collection<?> c) {
+        final Object[] a = c.toArray();
+        final int size = a.length;
+        if (size == 0)
+            return "[]";
+        int charLength = 0;
+
+        // Replace every array element with its string representation
+        for (int i = 0; i < size; i++) {
+            Object e = a[i];
+            // Extreme compatibility with AbstractCollection.toString()
+            String s = (e == c) ? "(this Collection)" : objectToString(e);
+            a[i] = s;
+            charLength += s.length();
+        }
+
+        return toString(a, size, charLength);
+    }
+
+    /**
+     * Like Arrays.toString(), but caller guarantees that size > 0,
+     * each element with index 0 <= i < size is a non-null String,
+     * and charLength is the sum of the lengths of the input Strings.
+     */
+    static String toString(Object[] a, int size, int charLength) {
+        // assert a != null;
+        // assert size > 0;
+
+        // Copy each string into a perfectly sized char[]
+        // Length of [ , , , ] == 2 * size
+        final char[] chars = new char[charLength + 2 * size];
+        chars[0] = '[';
+        int j = 1;
+        for (int i = 0; i < size; i++) {
+            if (i > 0) {
+                chars[j++] = ',';
+                chars[j++] = ' ';
+            }
+            String s = (String) a[i];
+            int len = s.length();
+            s.getChars(0, len, chars, j);
+            j += len;
+        }
+        chars[j] = ']';
+        // assert j == chars.length - 1;
+        return new String(chars);
+    }
+
+    /** Optimized form of: key + "=" + val */
+    static String mapEntryToString(Object key, Object val) {
+        final String k, v;
+        final int klen, vlen;
+        final char[] chars =
+            new char[(klen = (k = objectToString(key)).length()) +
+                     (vlen = (v = objectToString(val)).length()) + 1];
+        k.getChars(0, klen, chars, 0);
+        chars[klen] = '=';
+        v.getChars(0, vlen, chars, klen + 1);
+        return new String(chars);
+    }
+
+    private static String objectToString(Object x) {
+        // Extreme compatibility with StringBuilder.append(null)
+        String s;
+        return (x == null || (s = x.toString()) == null) ? "null" : s;
+    }
+}

src/java.base/share/classes/java/util/concurrent/RecursiveAction.java

@@ -0,0 +1,193 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent;
+
+/**
+ * A recursive resultless {@link ForkJoinTask}.  This class
+ * establishes conventions to parameterize resultless actions as
+ * {@code Void} {@code ForkJoinTask}s. Because {@code null} is the
+ * only valid value of type {@code Void}, methods such as {@code join}
+ * always return {@code null} upon completion.
+ *
+ * <p><b>Sample Usages.</b> Here is a simple but complete ForkJoin
+ * sort that sorts a given {@code long[]} array:
+ *
+ * <pre> {@code
+ * static class SortTask extends RecursiveAction {
+ *   final long[] array; final int lo, hi;
+ *   SortTask(long[] array, int lo, int hi) {
+ *     this.array = array; this.lo = lo; this.hi = hi;
+ *   }
+ *   SortTask(long[] array) { this(array, 0, array.length); }
+ *   protected void compute() {
+ *     if (hi - lo < THRESHOLD)
+ *       sortSequentially(lo, hi);
+ *     else {
+ *       int mid = (lo + hi) >>> 1;
+ *       invokeAll(new SortTask(array, lo, mid),
+ *                 new SortTask(array, mid, hi));
+ *       merge(lo, mid, hi);
+ *     }
+ *   }
+ *   // implementation details follow:
+ *   static final int THRESHOLD = 1000;
+ *   void sortSequentially(int lo, int hi) {
+ *     Arrays.sort(array, lo, hi);
+ *   }
+ *   void merge(int lo, int mid, int hi) {
+ *     long[] buf = Arrays.copyOfRange(array, lo, mid);
+ *     for (int i = 0, j = lo, k = mid; i < buf.length; j++)
+ *       array[j] = (k == hi || buf[i] < array[k]) ?
+ *         buf[i++] : array[k++];
+ *   }
+ * }}</pre>
+ *
+ * You could then sort {@code anArray} by creating {@code new
+ * SortTask(anArray)} and invoking it in a ForkJoinPool.  As a more
+ * concrete simple example, the following task increments each element
+ * of an array:
+ * <pre> {@code
+ * class IncrementTask extends RecursiveAction {
+ *   final long[] array; final int lo, hi;
+ *   IncrementTask(long[] array, int lo, int hi) {
+ *     this.array = array; this.lo = lo; this.hi = hi;
+ *   }
+ *   protected void compute() {
+ *     if (hi - lo < THRESHOLD) {
+ *       for (int i = lo; i < hi; ++i)
+ *         array[i]++;
+ *     }
+ *     else {
+ *       int mid = (lo + hi) >>> 1;
+ *       invokeAll(new IncrementTask(array, lo, mid),
+ *                 new IncrementTask(array, mid, hi));
+ *     }
+ *   }
+ * }}</pre>
+ *
+ * <p>The following example illustrates some refinements and idioms
+ * that may lead to better performance: RecursiveActions need not be
+ * fully recursive, so long as they maintain the basic
+ * divide-and-conquer approach. Here is a class that sums the squares
+ * of each element of a double array, by subdividing out only the
+ * right-hand-sides of repeated divisions by two, and keeping track of
+ * them with a chain of {@code next} references. It uses a dynamic
+ * threshold based on method {@code getSurplusQueuedTaskCount}, but
+ * counterbalances potential excess partitioning by directly
+ * performing leaf actions on unstolen tasks rather than further
+ * subdividing.
+ *
+ * <pre> {@code
+ * double sumOfSquares(ForkJoinPool pool, double[] array) {
+ *   int n = array.length;
+ *   Applyer a = new Applyer(array, 0, n, null);
+ *   pool.invoke(a);
+ *   return a.result;
+ * }
+ *
+ * class Applyer extends RecursiveAction {
+ *   final double[] array;
+ *   final int lo, hi;
+ *   double result;
+ *   Applyer next; // keeps track of right-hand-side tasks
+ *   Applyer(double[] array, int lo, int hi, Applyer next) {
+ *     this.array = array; this.lo = lo; this.hi = hi;
+ *     this.next = next;
+ *   }
+ *
+ *   double atLeaf(int l, int h) {
+ *     double sum = 0;
+ *     for (int i = l; i < h; ++i) // perform leftmost base step
+ *       sum += array[i] * array[i];
+ *     return sum;
+ *   }
+ *
+ *   protected void compute() {
+ *     int l = lo;
+ *     int h = hi;
+ *     Applyer right = null;
+ *     while (h - l > 1 && getSurplusQueuedTaskCount() <= 3) {
+ *       int mid = (l + h) >>> 1;
+ *       right = new Applyer(array, mid, h, right);
+ *       right.fork();
+ *       h = mid;
+ *     }
+ *     double sum = atLeaf(l, h);
+ *     while (right != null) {
+ *       if (right.tryUnfork()) // directly calculate if not stolen
+ *         sum += right.atLeaf(right.lo, right.hi);
+ *       else {
+ *         right.join();
+ *         sum += right.result;
+ *       }
+ *       right = right.next;
+ *     }
+ *     result = sum;
+ *   }
+ * }}</pre>
+ *
+ * @since 1.7
+ * @author Doug Lea
+ */
+public abstract class RecursiveAction extends ForkJoinTask<Void> {
+    private static final long serialVersionUID = 5232453952276485070L;
+
+    /**
+     * The main computation performed by this task.
+     */
+    protected abstract void compute();
+
+    /**
+     * Always returns {@code null}.
+     *
+     * @return {@code null} always
+     */
+    public final Void getRawResult() { return null; }
+
+    /**
+     * Requires null completion value.
+     */
+    protected final void setRawResult(Void mustBeNull) { }
+
+    /**
+     * Implements execution conventions for RecursiveActions.
+     */
+    protected final boolean exec() {
+        compute();
+        return true;
+    }
+
+}

src/java.base/share/classes/java/util/concurrent/RecursiveTask.java

@@ -0,0 +1,98 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent;
+
+/**
+ * A recursive result-bearing {@link ForkJoinTask}.
+ *
+ * <p>For a classic example, here is a task computing Fibonacci numbers:
+ *
+ * <pre> {@code
+ * class Fibonacci extends RecursiveTask<Integer> {
+ *   final int n;
+ *   Fibonacci(int n) { this.n = n; }
+ *   protected Integer compute() {
+ *     if (n <= 1)
+ *       return n;
+ *     Fibonacci f1 = new Fibonacci(n - 1);
+ *     f1.fork();
+ *     Fibonacci f2 = new Fibonacci(n - 2);
+ *     return f2.compute() + f1.join();
+ *   }
+ * }}</pre>
+ *
+ * However, besides being a dumb way to compute Fibonacci functions
+ * (there is a simple fast linear algorithm that you'd use in
+ * practice), this is likely to perform poorly because the smallest
+ * subtasks are too small to be worthwhile splitting up. Instead, as
+ * is the case for nearly all fork/join applications, you'd pick some
+ * minimum granularity size (for example 10 here) for which you always
+ * sequentially solve rather than subdividing.
+ *
+ * @since 1.7
+ * @author Doug Lea
+ */
+public abstract class RecursiveTask<V> extends ForkJoinTask<V> {
+    private static final long serialVersionUID = 5232453952276485270L;
+
+    /**
+     * The result of the computation.
+     */
+    V result;
+
+    /**
+     * The main computation performed by this task.
+     * @return the result of the computation
+     */
+    protected abstract V compute();
+
+    public final V getRawResult() {
+        return result;
+    }
+
+    protected final void setRawResult(V value) {
+        result = value;
+    }
+
+    /**
+     * Implements execution conventions for RecursiveTask.
+     */
+    protected final boolean exec() {
+        result = compute();
+        return true;
+    }
+
+}

src/java.base/share/classes/java/util/concurrent/RejectedExecutionException.java

@@ -0,0 +1,91 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent;
+
+/**
+ * Exception thrown by an {@link Executor} when a task cannot be
+ * accepted for execution.
+ *
+ * @since 1.5
+ * @author Doug Lea
+ */
+public class RejectedExecutionException extends RuntimeException {
+    private static final long serialVersionUID = -375805702767069545L;
+
+    /**
+     * Constructs a {@code RejectedExecutionException} with no detail message.
+     * The cause is not initialized, and may subsequently be
+     * initialized by a call to {@link #initCause(Throwable) initCause}.
+     */
+    public RejectedExecutionException() { }
+
+    /**
+     * Constructs a {@code RejectedExecutionException} with the
+     * specified detail message. The cause is not initialized, and may
+     * subsequently be initialized by a call to {@link
+     * #initCause(Throwable) initCause}.
+     *
+     * @param message the detail message
+     */
+    public RejectedExecutionException(String message) {
+        super(message);
+    }
+
+    /**
+     * Constructs a {@code RejectedExecutionException} with the
+     * specified detail message and cause.
+     *
+     * @param  message the detail message
+     * @param  cause the cause (which is saved for later retrieval by the
+     *         {@link #getCause()} method)
+     */
+    public RejectedExecutionException(String message, Throwable cause) {
+        super(message, cause);
+    }
+
+    /**
+     * Constructs a {@code RejectedExecutionException} with the
+     * specified cause.  The detail message is set to {@code (cause ==
+     * null ? null : cause.toString())} (which typically contains
+     * the class and detail message of {@code cause}).
+     *
+     * @param  cause the cause (which is saved for later retrieval by the
+     *         {@link #getCause()} method)
+     */
+    public RejectedExecutionException(Throwable cause) {
+        super(cause);
+    }
+}

src/java.base/share/classes/java/util/concurrent/RejectedExecutionHandler.java

@@ -0,0 +1,62 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent;
+
+/**
+ * A handler for tasks that cannot be executed by a {@link ThreadPoolExecutor}.
+ *
+ * @since 1.5
+ * @author Doug Lea
+ */
+public interface RejectedExecutionHandler {
+
+    /**
+     * Method that may be invoked by a {@link ThreadPoolExecutor} when
+     * {@link ThreadPoolExecutor#execute execute} cannot accept a
+     * task.  This may occur when no more threads or queue slots are
+     * available because their bounds would be exceeded, or upon
+     * shutdown of the Executor.
+     *
+     * <p>In the absence of other alternatives, the method may throw
+     * an unchecked {@link RejectedExecutionException}, which will be
+     * propagated to the caller of {@code execute}.
+     *
+     * @param r the runnable task requested to be executed
+     * @param executor the executor attempting to execute this task
+     * @throws RejectedExecutionException if there is no remedy
+     */
+    void rejectedExecution(Runnable r, ThreadPoolExecutor executor);
+}

src/java.base/share/classes/java/util/concurrent/RunnableFuture.java

@@ -0,0 +1,54 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent;
+
+/**
+ * A {@link Future} that is {@link Runnable}. Successful execution of
+ * the {@code run} method causes completion of the {@code Future}
+ * and allows access to its results.
+ * @see FutureTask
+ * @see Executor
+ * @since 1.6
+ * @author Doug Lea
+ * @param <V> The result type returned by this Future's {@code get} method
+ */
+public interface RunnableFuture<V> extends Runnable, Future<V> {
+    /**
+     * Sets this Future to the result of its computation
+     * unless it has been cancelled.
+     */
+    void run();
+}

src/java.base/share/classes/java/util/concurrent/RunnableScheduledFuture.java

@@ -0,0 +1,58 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent;
+
+/**
+ * A {@link ScheduledFuture} that is {@link Runnable}. Successful
+ * execution of the {@code run} method causes completion of the
+ * {@code Future} and allows access to its results.
+ * @see FutureTask
+ * @see Executor
+ * @since 1.6
+ * @author Doug Lea
+ * @param <V> The result type returned by this Future's {@code get} method
+ */
+public interface RunnableScheduledFuture<V> extends RunnableFuture<V>, ScheduledFuture<V> {
+
+    /**
+     * Returns {@code true} if this task is periodic. A periodic task may
+     * re-run according to some schedule. A non-periodic task can be
+     * run only once.
+     *
+     * @return {@code true} if this task is periodic
+     */
+    boolean isPeriodic();
+}

src/java.base/share/classes/java/util/concurrent/ScheduledExecutorService.java

@@ -0,0 +1,209 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent;
+
+/**
+ * An {@link ExecutorService} that can schedule commands to run after a given
+ * delay, or to execute periodically.
+ *
+ * <p>The {@code schedule} methods create tasks with various delays
+ * and return a task object that can be used to cancel or check
+ * execution. The {@code scheduleAtFixedRate} and
+ * {@code scheduleWithFixedDelay} methods create and execute tasks
+ * that run periodically until cancelled.
+ *
+ * <p>Commands submitted using the {@link Executor#execute(Runnable)}
+ * and {@link ExecutorService} {@code submit} methods are scheduled
+ * with a requested delay of zero. Zero and negative delays (but not
+ * periods) are also allowed in {@code schedule} methods, and are
+ * treated as requests for immediate execution.
+ *
+ * <p>All {@code schedule} methods accept <em>relative</em> delays and
+ * periods as arguments, not absolute times or dates. It is a simple
+ * matter to transform an absolute time represented as a {@link
+ * java.util.Date} to the required form. For example, to schedule at
+ * a certain future {@code date}, you can use: {@code schedule(task,
+ * date.getTime() - System.currentTimeMillis(),
+ * TimeUnit.MILLISECONDS)}. Beware however that expiration of a
+ * relative delay need not coincide with the current {@code Date} at
+ * which the task is enabled due to network time synchronization
+ * protocols, clock drift, or other factors.
+ *
+ * <p>The {@link Executors} class provides convenient factory methods for
+ * the ScheduledExecutorService implementations provided in this package.
+ *
+ * <h3>Usage Example</h3>
+ *
+ * Here is a class with a method that sets up a ScheduledExecutorService
+ * to beep every ten seconds for an hour:
+ *
+ * <pre> {@code
+ * import static java.util.concurrent.TimeUnit.*;
+ * class BeeperControl {
+ *   private final ScheduledExecutorService scheduler =
+ *     Executors.newScheduledThreadPool(1);
+ *
+ *   public void beepForAnHour() {
+ *     Runnable beeper = () -> System.out.println("beep");
+ *     ScheduledFuture<?> beeperHandle =
+ *       scheduler.scheduleAtFixedRate(beeper, 10, 10, SECONDS);
+ *     Runnable canceller = () -> beeperHandle.cancel(false);
+ *     scheduler.schedule(canceller, 1, HOURS);
+ *   }
+ * }}</pre>
+ *
+ * @since 1.5
+ * @author Doug Lea
+ */
+public interface ScheduledExecutorService extends ExecutorService {
+
+    /**
+     * Submits a one-shot task that becomes enabled after the given delay.
+     *
+     * @param command the task to execute
+     * @param delay the time from now to delay execution
+     * @param unit the time unit of the delay parameter
+     * @return a ScheduledFuture representing pending completion of
+     *         the task and whose {@code get()} method will return
+     *         {@code null} upon completion
+     * @throws RejectedExecutionException if the task cannot be
+     *         scheduled for execution
+     * @throws NullPointerException if command or unit is null
+     */
+    public ScheduledFuture<?> schedule(Runnable command,
+                                       long delay, TimeUnit unit);
+
+    /**
+     * Submits a value-returning one-shot task that becomes enabled
+     * after the given delay.
+     *
+     * @param callable the function to execute
+     * @param delay the time from now to delay execution
+     * @param unit the time unit of the delay parameter
+     * @param <V> the type of the callable's result
+     * @return a ScheduledFuture that can be used to extract result or cancel
+     * @throws RejectedExecutionException if the task cannot be
+     *         scheduled for execution
+     * @throws NullPointerException if callable or unit is null
+     */
+    public <V> ScheduledFuture<V> schedule(Callable<V> callable,
+                                           long delay, TimeUnit unit);
+
+    /**
+     * Submits a periodic action that becomes enabled first after the
+     * given initial delay, and subsequently with the given period;
+     * that is, executions will commence after
+     * {@code initialDelay}, then {@code initialDelay + period}, then
+     * {@code initialDelay + 2 * period}, and so on.
+     *
+     * <p>The sequence of task executions continues indefinitely until
+     * one of the following exceptional completions occur:
+     * <ul>
+     * <li>The task is {@linkplain Future#cancel explicitly cancelled}
+     * via the returned future.
+     * <li>The executor terminates, also resulting in task cancellation.
+     * <li>An execution of the task throws an exception.  In this case
+     * calling {@link Future#get() get} on the returned future will throw
+     * {@link ExecutionException}, holding the exception as its cause.
+     * </ul>
+     * Subsequent executions are suppressed.  Subsequent calls to
+     * {@link Future#isDone isDone()} on the returned future will
+     * return {@code true}.
+     *
+     * <p>If any execution of this task takes longer than its period, then
+     * subsequent executions may start late, but will not concurrently
+     * execute.
+     *
+     * @param command the task to execute
+     * @param initialDelay the time to delay first execution
+     * @param period the period between successive executions
+     * @param unit the time unit of the initialDelay and period parameters
+     * @return a ScheduledFuture representing pending completion of
+     *         the series of repeated tasks.  The future's {@link
+     *         Future#get() get()} method will never return normally,
+     *         and will throw an exception upon task cancellation or
+     *         abnormal termination of a task execution.
+     * @throws RejectedExecutionException if the task cannot be
+     *         scheduled for execution
+     * @throws NullPointerException if command or unit is null
+     * @throws IllegalArgumentException if period less than or equal to zero
+     */
+    public ScheduledFuture<?> scheduleAtFixedRate(Runnable command,
+                                                  long initialDelay,
+                                                  long period,
+                                                  TimeUnit unit);
+
+    /**
+     * Submits a periodic action that becomes enabled first after the
+     * given initial delay, and subsequently with the given delay
+     * between the termination of one execution and the commencement of
+     * the next.
+     *
+     * <p>The sequence of task executions continues indefinitely until
+     * one of the following exceptional completions occur:
+     * <ul>
+     * <li>The task is {@linkplain Future#cancel explicitly cancelled}
+     * via the returned future.
+     * <li>The executor terminates, also resulting in task cancellation.
+     * <li>An execution of the task throws an exception.  In this case
+     * calling {@link Future#get() get} on the returned future will throw
+     * {@link ExecutionException}, holding the exception as its cause.
+     * </ul>
+     * Subsequent executions are suppressed.  Subsequent calls to
+     * {@link Future#isDone isDone()} on the returned future will
+     * return {@code true}.
+     *
+     * @param command the task to execute
+     * @param initialDelay the time to delay first execution
+     * @param delay the delay between the termination of one
+     * execution and the commencement of the next
+     * @param unit the time unit of the initialDelay and delay parameters
+     * @return a ScheduledFuture representing pending completion of
+     *         the series of repeated tasks.  The future's {@link
+     *         Future#get() get()} method will never return normally,
+     *         and will throw an exception upon task cancellation or
+     *         abnormal termination of a task execution.
+     * @throws RejectedExecutionException if the task cannot be
+     *         scheduled for execution
+     * @throws NullPointerException if command or unit is null
+     * @throws IllegalArgumentException if delay less than or equal to zero
+     */
+    public ScheduledFuture<?> scheduleWithFixedDelay(Runnable command,
+                                                     long initialDelay,
+                                                     long delay,
+                                                     TimeUnit unit);
+
+}

src/java.base/share/classes/java/util/concurrent/ScheduledFuture.java

@@ -0,0 +1,48 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent;
+
+/**
+ * A delayed result-bearing action that can be cancelled.
+ * Usually a scheduled future is the result of scheduling
+ * a task with a {@link ScheduledExecutorService}.
+ *
+ * @since 1.5
+ * @author Doug Lea
+ * @param <V> The result type returned by this Future
+ */
+public interface ScheduledFuture<V> extends Delayed, Future<V> {
+}

src/java.base/share/classes/java/util/concurrent/Semaphore.java

@@ -0,0 +1,720 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent;
+
+import java.util.Collection;
+import java.util.concurrent.locks.AbstractQueuedSynchronizer;
+
+/**
+ * A counting semaphore.  Conceptually, a semaphore maintains a set of
+ * permits.  Each {@link #acquire} blocks if necessary until a permit is
+ * available, and then takes it.  Each {@link #release} adds a permit,
+ * potentially releasing a blocking acquirer.
+ * However, no actual permit objects are used; the {@code Semaphore} just
+ * keeps a count of the number available and acts accordingly.
+ *
+ * <p>Semaphores are often used to restrict the number of threads than can
+ * access some (physical or logical) resource. For example, here is
+ * a class that uses a semaphore to control access to a pool of items:
+ * <pre> {@code
+ * class Pool {
+ *   private static final int MAX_AVAILABLE = 100;
+ *   private final Semaphore available = new Semaphore(MAX_AVAILABLE, true);
+ *
+ *   public Object getItem() throws InterruptedException {
+ *     available.acquire();
+ *     return getNextAvailableItem();
+ *   }
+ *
+ *   public void putItem(Object x) {
+ *     if (markAsUnused(x))
+ *       available.release();
+ *   }
+ *
+ *   // Not a particularly efficient data structure; just for demo
+ *
+ *   protected Object[] items = ... whatever kinds of items being managed
+ *   protected boolean[] used = new boolean[MAX_AVAILABLE];
+ *
+ *   protected synchronized Object getNextAvailableItem() {
+ *     for (int i = 0; i < MAX_AVAILABLE; ++i) {
+ *       if (!used[i]) {
+ *         used[i] = true;
+ *         return items[i];
+ *       }
+ *     }
+ *     return null; // not reached
+ *   }
+ *
+ *   protected synchronized boolean markAsUnused(Object item) {
+ *     for (int i = 0; i < MAX_AVAILABLE; ++i) {
+ *       if (item == items[i]) {
+ *         if (used[i]) {
+ *           used[i] = false;
+ *           return true;
+ *         } else
+ *           return false;
+ *       }
+ *     }
+ *     return false;
+ *   }
+ * }}</pre>
+ *
+ * <p>Before obtaining an item each thread must acquire a permit from
+ * the semaphore, guaranteeing that an item is available for use. When
+ * the thread has finished with the item it is returned back to the
+ * pool and a permit is returned to the semaphore, allowing another
+ * thread to acquire that item.  Note that no synchronization lock is
+ * held when {@link #acquire} is called as that would prevent an item
+ * from being returned to the pool.  The semaphore encapsulates the
+ * synchronization needed to restrict access to the pool, separately
+ * from any synchronization needed to maintain the consistency of the
+ * pool itself.
+ *
+ * <p>A semaphore initialized to one, and which is used such that it
+ * only has at most one permit available, can serve as a mutual
+ * exclusion lock.  This is more commonly known as a <em>binary
+ * semaphore</em>, because it only has two states: one permit
+ * available, or zero permits available.  When used in this way, the
+ * binary semaphore has the property (unlike many {@link java.util.concurrent.locks.Lock}
+ * implementations), that the &quot;lock&quot; can be released by a
+ * thread other than the owner (as semaphores have no notion of
+ * ownership).  This can be useful in some specialized contexts, such
+ * as deadlock recovery.
+ *
+ * <p>The constructor for this class optionally accepts a
+ * <em>fairness</em> parameter. When set false, this class makes no
+ * guarantees about the order in which threads acquire permits. In
+ * particular, <em>barging</em> is permitted, that is, a thread
+ * invoking {@link #acquire} can be allocated a permit ahead of a
+ * thread that has been waiting - logically the new thread places itself at
+ * the head of the queue of waiting threads. When fairness is set true, the
+ * semaphore guarantees that threads invoking any of the {@link
+ * #acquire() acquire} methods are selected to obtain permits in the order in
+ * which their invocation of those methods was processed
+ * (first-in-first-out; FIFO). Note that FIFO ordering necessarily
+ * applies to specific internal points of execution within these
+ * methods.  So, it is possible for one thread to invoke
+ * {@code acquire} before another, but reach the ordering point after
+ * the other, and similarly upon return from the method.
+ * Also note that the untimed {@link #tryAcquire() tryAcquire} methods do not
+ * honor the fairness setting, but will take any permits that are
+ * available.
+ *
+ * <p>Generally, semaphores used to control resource access should be
+ * initialized as fair, to ensure that no thread is starved out from
+ * accessing a resource. When using semaphores for other kinds of
+ * synchronization control, the throughput advantages of non-fair
+ * ordering often outweigh fairness considerations.
+ *
+ * <p>This class also provides convenience methods to {@link
+ * #acquire(int) acquire} and {@link #release(int) release} multiple
+ * permits at a time. These methods are generally more efficient and
+ * effective than loops. However, they do not establish any preference
+ * order. For example, if thread A invokes {@code s.acquire(3}) and
+ * thread B invokes {@code s.acquire(2)}, and two permits become
+ * available, then there is no guarantee that thread B will obtain
+ * them unless its acquire came first and Semaphore {@code s} is in
+ * fair mode.
+ *
+ * <p>Memory consistency effects: Actions in a thread prior to calling
+ * a "release" method such as {@code release()}
+ * <a href="package-summary.html#MemoryVisibility"><i>happen-before</i></a>
+ * actions following a successful "acquire" method such as {@code acquire()}
+ * in another thread.
+ *
+ * @since 1.5
+ * @author Doug Lea
+ */
+public class Semaphore implements java.io.Serializable {
+    private static final long serialVersionUID = -3222578661600680210L;
+    /** All mechanics via AbstractQueuedSynchronizer subclass */
+    private final Sync sync;
+
+    /**
+     * Synchronization implementation for semaphore.  Uses AQS state
+     * to represent permits. Subclassed into fair and nonfair
+     * versions.
+     */
+    abstract static class Sync extends AbstractQueuedSynchronizer {
+        private static final long serialVersionUID = 1192457210091910933L;
+
+        Sync(int permits) {
+            setState(permits);
+        }
+
+        final int getPermits() {
+            return getState();
+        }
+
+        final int nonfairTryAcquireShared(int acquires) {
+            for (;;) {
+                int available = getState();
+                int remaining = available - acquires;
+                if (remaining < 0 ||
+                    compareAndSetState(available, remaining))
+                    return remaining;
+            }
+        }
+
+        protected final boolean tryReleaseShared(int releases) {
+            for (;;) {
+                int current = getState();
+                int next = current + releases;
+                if (next < current) // overflow
+                    throw new Error("Maximum permit count exceeded");
+                if (compareAndSetState(current, next))
+                    return true;
+            }
+        }
+
+        final void reducePermits(int reductions) {
+            for (;;) {
+                int current = getState();
+                int next = current - reductions;
+                if (next > current) // underflow
+                    throw new Error("Permit count underflow");
+                if (compareAndSetState(current, next))
+                    return;
+            }
+        }
+
+        final int drainPermits() {
+            for (;;) {
+                int current = getState();
+                if (current == 0 || compareAndSetState(current, 0))
+                    return current;
+            }
+        }
+    }
+
+    /**
+     * NonFair version
+     */
+    static final class NonfairSync extends Sync {
+        private static final long serialVersionUID = -2694183684443567898L;
+
+        NonfairSync(int permits) {
+            super(permits);
+        }
+
+        protected int tryAcquireShared(int acquires) {
+            return nonfairTryAcquireShared(acquires);
+        }
+    }
+
+    /**
+     * Fair version
+     */
+    static final class FairSync extends Sync {
+        private static final long serialVersionUID = 2014338818796000944L;
+
+        FairSync(int permits) {
+            super(permits);
+        }
+
+        protected int tryAcquireShared(int acquires) {
+            for (;;) {
+                if (hasQueuedPredecessors())
+                    return -1;
+                int available = getState();
+                int remaining = available - acquires;
+                if (remaining < 0 ||
+                    compareAndSetState(available, remaining))
+                    return remaining;
+            }
+        }
+    }
+
+    /**
+     * Creates a {@code Semaphore} with the given number of
+     * permits and nonfair fairness setting.
+     *
+     * @param permits the initial number of permits available.
+     *        This value may be negative, in which case releases
+     *        must occur before any acquires will be granted.
+     */
+    public Semaphore(int permits) {
+        sync = new NonfairSync(permits);
+    }
+
+    /**
+     * Creates a {@code Semaphore} with the given number of
+     * permits and the given fairness setting.
+     *
+     * @param permits the initial number of permits available.
+     *        This value may be negative, in which case releases
+     *        must occur before any acquires will be granted.
+     * @param fair {@code true} if this semaphore will guarantee
+     *        first-in first-out granting of permits under contention,
+     *        else {@code false}
+     */
+    public Semaphore(int permits, boolean fair) {
+        sync = fair ? new FairSync(permits) : new NonfairSync(permits);
+    }
+
+    /**
+     * Acquires a permit from this semaphore, blocking until one is
+     * available, or the thread is {@linkplain Thread#interrupt interrupted}.
+     *
+     * <p>Acquires a permit, if one is available and returns immediately,
+     * reducing the number of available permits by one.
+     *
+     * <p>If no permit is available then the current thread becomes
+     * disabled for thread scheduling purposes and lies dormant until
+     * one of two things happens:
+     * <ul>
+     * <li>Some other thread invokes the {@link #release} method for this
+     * semaphore and the current thread is next to be assigned a permit; or
+     * <li>Some other thread {@linkplain Thread#interrupt interrupts}
+     * the current thread.
+     * </ul>
+     *
+     * <p>If the current thread:
+     * <ul>
+     * <li>has its interrupted status set on entry to this method; or
+     * <li>is {@linkplain Thread#interrupt interrupted} while waiting
+     * for a permit,
+     * </ul>
+     * then {@link InterruptedException} is thrown and the current thread's
+     * interrupted status is cleared.
+     *
+     * @throws InterruptedException if the current thread is interrupted
+     */
+    public void acquire() throws InterruptedException {
+        sync.acquireSharedInterruptibly(1);
+    }
+
+    /**
+     * Acquires a permit from this semaphore, blocking until one is
+     * available.
+     *
+     * <p>Acquires a permit, if one is available and returns immediately,
+     * reducing the number of available permits by one.
+     *
+     * <p>If no permit is available then the current thread becomes
+     * disabled for thread scheduling purposes and lies dormant until
+     * some other thread invokes the {@link #release} method for this
+     * semaphore and the current thread is next to be assigned a permit.
+     *
+     * <p>If the current thread is {@linkplain Thread#interrupt interrupted}
+     * while waiting for a permit then it will continue to wait, but the
+     * time at which the thread is assigned a permit may change compared to
+     * the time it would have received the permit had no interruption
+     * occurred.  When the thread does return from this method its interrupt
+     * status will be set.
+     */
+    public void acquireUninterruptibly() {
+        sync.acquireShared(1);
+    }
+
+    /**
+     * Acquires a permit from this semaphore, only if one is available at the
+     * time of invocation.
+     *
+     * <p>Acquires a permit, if one is available and returns immediately,
+     * with the value {@code true},
+     * reducing the number of available permits by one.
+     *
+     * <p>If no permit is available then this method will return
+     * immediately with the value {@code false}.
+     *
+     * <p>Even when this semaphore has been set to use a
+     * fair ordering policy, a call to {@code tryAcquire()} <em>will</em>
+     * immediately acquire a permit if one is available, whether or not
+     * other threads are currently waiting.
+     * This &quot;barging&quot; behavior can be useful in certain
+     * circumstances, even though it breaks fairness. If you want to honor
+     * the fairness setting, then use
+     * {@link #tryAcquire(long, TimeUnit) tryAcquire(0, TimeUnit.SECONDS)}
+     * which is almost equivalent (it also detects interruption).
+     *
+     * @return {@code true} if a permit was acquired and {@code false}
+     *         otherwise
+     */
+    public boolean tryAcquire() {
+        return sync.nonfairTryAcquireShared(1) >= 0;
+    }
+
+    /**
+     * Acquires a permit from this semaphore, if one becomes available
+     * within the given waiting time and the current thread has not
+     * been {@linkplain Thread#interrupt interrupted}.
+     *
+     * <p>Acquires a permit, if one is available and returns immediately,
+     * with the value {@code true},
+     * reducing the number of available permits by one.
+     *
+     * <p>If no permit is available then the current thread becomes
+     * disabled for thread scheduling purposes and lies dormant until
+     * one of three things happens:
+     * <ul>
+     * <li>Some other thread invokes the {@link #release} method for this
+     * semaphore and the current thread is next to be assigned a permit; or
+     * <li>Some other thread {@linkplain Thread#interrupt interrupts}
+     * the current thread; or
+     * <li>The specified waiting time elapses.
+     * </ul>
+     *
+     * <p>If a permit is acquired then the value {@code true} is returned.
+     *
+     * <p>If the current thread:
+     * <ul>
+     * <li>has its interrupted status set on entry to this method; or
+     * <li>is {@linkplain Thread#interrupt interrupted} while waiting
+     * to acquire a permit,
+     * </ul>
+     * then {@link InterruptedException} is thrown and the current thread's
+     * interrupted status is cleared.
+     *
+     * <p>If the specified waiting time elapses then the value {@code false}
+     * is returned.  If the time is less than or equal to zero, the method
+     * will not wait at all.
+     *
+     * @param timeout the maximum time to wait for a permit
+     * @param unit the time unit of the {@code timeout} argument
+     * @return {@code true} if a permit was acquired and {@code false}
+     *         if the waiting time elapsed before a permit was acquired
+     * @throws InterruptedException if the current thread is interrupted
+     */
+    public boolean tryAcquire(long timeout, TimeUnit unit)
+        throws InterruptedException {
+        return sync.tryAcquireSharedNanos(1, unit.toNanos(timeout));
+    }
+
+    /**
+     * Releases a permit, returning it to the semaphore.
+     *
+     * <p>Releases a permit, increasing the number of available permits by
+     * one.  If any threads are trying to acquire a permit, then one is
+     * selected and given the permit that was just released.  That thread
+     * is (re)enabled for thread scheduling purposes.
+     *
+     * <p>There is no requirement that a thread that releases a permit must
+     * have acquired that permit by calling {@link #acquire}.
+     * Correct usage of a semaphore is established by programming convention
+     * in the application.
+     */
+    public void release() {
+        sync.releaseShared(1);
+    }
+
+    /**
+     * Acquires the given number of permits from this semaphore,
+     * blocking until all are available,
+     * or the thread is {@linkplain Thread#interrupt interrupted}.
+     *
+     * <p>Acquires the given number of permits, if they are available,
+     * and returns immediately, reducing the number of available permits
+     * by the given amount. This method has the same effect as the
+     * loop {@code for (int i = 0; i < permits; ++i) acquire();} except
+     * that it atomically acquires the permits all at once:
+     *
+     * <p>If insufficient permits are available then the current thread becomes
+     * disabled for thread scheduling purposes and lies dormant until
+     * one of two things happens:
+     * <ul>
+     * <li>Some other thread invokes one of the {@link #release() release}
+     * methods for this semaphore and the current thread is next to be assigned
+     * permits and the number of available permits satisfies this request; or
+     * <li>Some other thread {@linkplain Thread#interrupt interrupts}
+     * the current thread.
+     * </ul>
+     *
+     * <p>If the current thread:
+     * <ul>
+     * <li>has its interrupted status set on entry to this method; or
+     * <li>is {@linkplain Thread#interrupt interrupted} while waiting
+     * for a permit,
+     * </ul>
+     * then {@link InterruptedException} is thrown and the current thread's
+     * interrupted status is cleared.
+     * Any permits that were to be assigned to this thread are instead
+     * assigned to other threads trying to acquire permits, as if
+     * permits had been made available by a call to {@link #release()}.
+     *
+     * @param permits the number of permits to acquire
+     * @throws InterruptedException if the current thread is interrupted
+     * @throws IllegalArgumentException if {@code permits} is negative
+     */
+    public void acquire(int permits) throws InterruptedException {
+        if (permits < 0) throw new IllegalArgumentException();
+        sync.acquireSharedInterruptibly(permits);
+    }
+
+    /**
+     * Acquires the given number of permits from this semaphore,
+     * blocking until all are available.
+     *
+     * <p>Acquires the given number of permits, if they are available,
+     * and returns immediately, reducing the number of available permits
+     * by the given amount. This method has the same effect as the
+     * loop {@code for (int i = 0; i < permits; ++i) acquireUninterruptibly();}
+     * except that it atomically acquires the permits all at once:
+     *
+     * <p>If insufficient permits are available then the current thread becomes
+     * disabled for thread scheduling purposes and lies dormant until
+     * some other thread invokes one of the {@link #release() release}
+     * methods for this semaphore and the current thread is next to be assigned
+     * permits and the number of available permits satisfies this request.
+     *
+     * <p>If the current thread is {@linkplain Thread#interrupt interrupted}
+     * while waiting for permits then it will continue to wait and its
+     * position in the queue is not affected.  When the thread does return
+     * from this method its interrupt status will be set.
+     *
+     * @param permits the number of permits to acquire
+     * @throws IllegalArgumentException if {@code permits} is negative
+     */
+    public void acquireUninterruptibly(int permits) {
+        if (permits < 0) throw new IllegalArgumentException();
+        sync.acquireShared(permits);
+    }
+
+    /**
+     * Acquires the given number of permits from this semaphore, only
+     * if all are available at the time of invocation.
+     *
+     * <p>Acquires the given number of permits, if they are available, and
+     * returns immediately, with the value {@code true},
+     * reducing the number of available permits by the given amount.
+     *
+     * <p>If insufficient permits are available then this method will return
+     * immediately with the value {@code false} and the number of available
+     * permits is unchanged.
+     *
+     * <p>Even when this semaphore has been set to use a fair ordering
+     * policy, a call to {@code tryAcquire} <em>will</em>
+     * immediately acquire a permit if one is available, whether or
+     * not other threads are currently waiting.  This
+     * &quot;barging&quot; behavior can be useful in certain
+     * circumstances, even though it breaks fairness. If you want to
+     * honor the fairness setting, then use {@link #tryAcquire(int,
+     * long, TimeUnit) tryAcquire(permits, 0, TimeUnit.SECONDS)}
+     * which is almost equivalent (it also detects interruption).
+     *
+     * @param permits the number of permits to acquire
+     * @return {@code true} if the permits were acquired and
+     *         {@code false} otherwise
+     * @throws IllegalArgumentException if {@code permits} is negative
+     */
+    public boolean tryAcquire(int permits) {
+        if (permits < 0) throw new IllegalArgumentException();
+        return sync.nonfairTryAcquireShared(permits) >= 0;
+    }
+
+    /**
+     * Acquires the given number of permits from this semaphore, if all
+     * become available within the given waiting time and the current
+     * thread has not been {@linkplain Thread#interrupt interrupted}.
+     *
+     * <p>Acquires the given number of permits, if they are available and
+     * returns immediately, with the value {@code true},
+     * reducing the number of available permits by the given amount.
+     *
+     * <p>If insufficient permits are available then
+     * the current thread becomes disabled for thread scheduling
+     * purposes and lies dormant until one of three things happens:
+     * <ul>
+     * <li>Some other thread invokes one of the {@link #release() release}
+     * methods for this semaphore and the current thread is next to be assigned
+     * permits and the number of available permits satisfies this request; or
+     * <li>Some other thread {@linkplain Thread#interrupt interrupts}
+     * the current thread; or
+     * <li>The specified waiting time elapses.
+     * </ul>
+     *
+     * <p>If the permits are acquired then the value {@code true} is returned.
+     *
+     * <p>If the current thread:
+     * <ul>
+     * <li>has its interrupted status set on entry to this method; or
+     * <li>is {@linkplain Thread#interrupt interrupted} while waiting
+     * to acquire the permits,
+     * </ul>
+     * then {@link InterruptedException} is thrown and the current thread's
+     * interrupted status is cleared.
+     * Any permits that were to be assigned to this thread, are instead
+     * assigned to other threads trying to acquire permits, as if
+     * the permits had been made available by a call to {@link #release()}.
+     *
+     * <p>If the specified waiting time elapses then the value {@code false}
+     * is returned.  If the time is less than or equal to zero, the method
+     * will not wait at all.  Any permits that were to be assigned to this
+     * thread, are instead assigned to other threads trying to acquire
+     * permits, as if the permits had been made available by a call to
+     * {@link #release()}.
+     *
+     * @param permits the number of permits to acquire
+     * @param timeout the maximum time to wait for the permits
+     * @param unit the time unit of the {@code timeout} argument
+     * @return {@code true} if all permits were acquired and {@code false}
+     *         if the waiting time elapsed before all permits were acquired
+     * @throws InterruptedException if the current thread is interrupted
+     * @throws IllegalArgumentException if {@code permits} is negative
+     */
+    public boolean tryAcquire(int permits, long timeout, TimeUnit unit)
+        throws InterruptedException {
+        if (permits < 0) throw new IllegalArgumentException();
+        return sync.tryAcquireSharedNanos(permits, unit.toNanos(timeout));
+    }
+
+    /**
+     * Releases the given number of permits, returning them to the semaphore.
+     *
+     * <p>Releases the given number of permits, increasing the number of
+     * available permits by that amount.
+     * If any threads are trying to acquire permits, then one thread
+     * is selected and given the permits that were just released.
+     * If the number of available permits satisfies that thread's request
+     * then that thread is (re)enabled for thread scheduling purposes;
+     * otherwise the thread will wait until sufficient permits are available.
+     * If there are still permits available
+     * after this thread's request has been satisfied, then those permits
+     * are assigned in turn to other threads trying to acquire permits.
+     *
+     * <p>There is no requirement that a thread that releases a permit must
+     * have acquired that permit by calling {@link Semaphore#acquire acquire}.
+     * Correct usage of a semaphore is established by programming convention
+     * in the application.
+     *
+     * @param permits the number of permits to release
+     * @throws IllegalArgumentException if {@code permits} is negative
+     */
+    public void release(int permits) {
+        if (permits < 0) throw new IllegalArgumentException();
+        sync.releaseShared(permits);
+    }
+
+    /**
+     * Returns the current number of permits available in this semaphore.
+     *
+     * <p>This method is typically used for debugging and testing purposes.
+     *
+     * @return the number of permits available in this semaphore
+     */
+    public int availablePermits() {
+        return sync.getPermits();
+    }
+
+    /**
+     * Acquires and returns all permits that are immediately
+     * available, or if negative permits are available, releases them.
+     * Upon return, zero permits are available.
+     *
+     * @return the number of permits acquired or, if negative, the
+     * number released
+     */
+    public int drainPermits() {
+        return sync.drainPermits();
+    }
+
+    /**
+     * Shrinks the number of available permits by the indicated
+     * reduction. This method can be useful in subclasses that use
+     * semaphores to track resources that become unavailable. This
+     * method differs from {@code acquire} in that it does not block
+     * waiting for permits to become available.
+     *
+     * @param reduction the number of permits to remove
+     * @throws IllegalArgumentException if {@code reduction} is negative
+     */
+    protected void reducePermits(int reduction) {
+        if (reduction < 0) throw new IllegalArgumentException();
+        sync.reducePermits(reduction);
+    }
+
+    /**
+     * Returns {@code true} if this semaphore has fairness set true.
+     *
+     * @return {@code true} if this semaphore has fairness set true
+     */
+    public boolean isFair() {
+        return sync instanceof FairSync;
+    }
+
+    /**
+     * Queries whether any threads are waiting to acquire. Note that
+     * because cancellations may occur at any time, a {@code true}
+     * return does not guarantee that any other thread will ever
+     * acquire.  This method is designed primarily for use in
+     * monitoring of the system state.
+     *
+     * @return {@code true} if there may be other threads waiting to
+     *         acquire the lock
+     */
+    public final boolean hasQueuedThreads() {
+        return sync.hasQueuedThreads();
+    }
+
+    /**
+     * Returns an estimate of the number of threads waiting to acquire.
+     * The value is only an estimate because the number of threads may
+     * change dynamically while this method traverses internal data
+     * structures.  This method is designed for use in monitoring
+     * system state, not for synchronization control.
+     *
+     * @return the estimated number of threads waiting for this lock
+     */
+    public final int getQueueLength() {
+        return sync.getQueueLength();
+    }
+
+    /**
+     * Returns a collection containing threads that may be waiting to acquire.
+     * Because the actual set of threads may change dynamically while
+     * constructing this result, the returned collection is only a best-effort
+     * estimate.  The elements of the returned collection are in no particular
+     * order.  This method is designed to facilitate construction of
+     * subclasses that provide more extensive monitoring facilities.
+     *
+     * @return the collection of threads
+     */
+    protected Collection<Thread> getQueuedThreads() {
+        return sync.getQueuedThreads();
+    }
+
+    /**
+     * Returns a string identifying this semaphore, as well as its state.
+     * The state, in brackets, includes the String {@code "Permits ="}
+     * followed by the number of permits.
+     *
+     * @return a string identifying this semaphore, as well as its state
+     */
+    public String toString() {
+        return super.toString() + "[Permits = " + sync.getPermits() + "]";
+    }
+}

src/java.base/share/classes/java/util/concurrent/ThreadFactory.java

@@ -0,0 +1,69 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent;
+
+/**
+ * An object that creates new threads on demand.  Using thread factories
+ * removes hardwiring of calls to {@link Thread#Thread(Runnable) new Thread},
+ * enabling applications to use special thread subclasses, priorities, etc.
+ *
+ * <p>
+ * The simplest implementation of this interface is just:
+ * <pre> {@code
+ * class SimpleThreadFactory implements ThreadFactory {
+ *   public Thread newThread(Runnable r) {
+ *     return new Thread(r);
+ *   }
+ * }}</pre>
+ *
+ * The {@link Executors#defaultThreadFactory} method provides a more
+ * useful simple implementation, that sets the created thread context
+ * to known values before returning it.
+ * @since 1.5
+ * @author Doug Lea
+ */
+public interface ThreadFactory {
+
+    /**
+     * Constructs a new {@code Thread}.  Implementations may also initialize
+     * priority, name, daemon status, {@code ThreadGroup}, etc.
+     *
+     * @param r a runnable to be executed by new thread instance
+     * @return constructed thread, or {@code null} if the request to
+     *         create a thread is rejected
+     */
+    Thread newThread(Runnable r);
+}

src/java.base/share/classes/java/util/concurrent/TimeUnit.java

@@ -0,0 +1,449 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent;
+
+import java.time.temporal.ChronoUnit;
+import java.util.Objects;
+
+/**
+ * A {@code TimeUnit} represents time durations at a given unit of
+ * granularity and provides utility methods to convert across units,
+ * and to perform timing and delay operations in these units.  A
+ * {@code TimeUnit} does not maintain time information, but only
+ * helps organize and use time representations that may be maintained
+ * separately across various contexts.  A nanosecond is defined as one
+ * thousandth of a microsecond, a microsecond as one thousandth of a
+ * millisecond, a millisecond as one thousandth of a second, a minute
+ * as sixty seconds, an hour as sixty minutes, and a day as twenty four
+ * hours.
+ *
+ * <p>A {@code TimeUnit} is mainly used to inform time-based methods
+ * how a given timing parameter should be interpreted. For example,
+ * the following code will timeout in 50 milliseconds if the {@link
+ * java.util.concurrent.locks.Lock lock} is not available:
+ *
+ * <pre> {@code
+ * Lock lock = ...;
+ * if (lock.tryLock(50L, TimeUnit.MILLISECONDS)) ...}</pre>
+ *
+ * while this code will timeout in 50 seconds:
+ * <pre> {@code
+ * Lock lock = ...;
+ * if (lock.tryLock(50L, TimeUnit.SECONDS)) ...}</pre>
+ *
+ * Note however, that there is no guarantee that a particular timeout
+ * implementation will be able to notice the passage of time at the
+ * same granularity as the given {@code TimeUnit}.
+ *
+ * @since 1.5
+ * @author Doug Lea
+ */
+public enum TimeUnit {
+    /**
+     * Time unit representing one thousandth of a microsecond.
+     */
+    NANOSECONDS(TimeUnit.NANO_SCALE),
+    /**
+     * Time unit representing one thousandth of a millisecond.
+     */
+    MICROSECONDS(TimeUnit.MICRO_SCALE),
+    /**
+     * Time unit representing one thousandth of a second.
+     */
+    MILLISECONDS(TimeUnit.MILLI_SCALE),
+    /**
+     * Time unit representing one second.
+     */
+    SECONDS(TimeUnit.SECOND_SCALE),
+    /**
+     * Time unit representing sixty seconds.
+     * @since 1.6
+     */
+    MINUTES(TimeUnit.MINUTE_SCALE),
+    /**
+     * Time unit representing sixty minutes.
+     * @since 1.6
+     */
+    HOURS(TimeUnit.HOUR_SCALE),
+    /**
+     * Time unit representing twenty four hours.
+     * @since 1.6
+     */
+    DAYS(TimeUnit.DAY_SCALE);
+
+    // Scales as constants
+    private static final long NANO_SCALE   = 1L;
+    private static final long MICRO_SCALE  = 1000L * NANO_SCALE;
+    private static final long MILLI_SCALE  = 1000L * MICRO_SCALE;
+    private static final long SECOND_SCALE = 1000L * MILLI_SCALE;
+    private static final long MINUTE_SCALE = 60L * SECOND_SCALE;
+    private static final long HOUR_SCALE   = 60L * MINUTE_SCALE;
+    private static final long DAY_SCALE    = 24L * HOUR_SCALE;
+
+    /*
+     * Instances cache conversion ratios and saturation cutoffs for
+     * the units up through SECONDS. Other cases compute them, in
+     * method cvt.
+     */
+
+    private final long scale;
+    private final long maxNanos;
+    private final long maxMicros;
+    private final long maxMillis;
+    private final long maxSecs;
+    private final long microRatio;
+    private final int milliRatio;   // fits in 32 bits
+    private final int secRatio;     // fits in 32 bits
+
+    private TimeUnit(long s) {
+        this.scale = s;
+        this.maxNanos = Long.MAX_VALUE / s;
+        long ur = (s >= MICRO_SCALE) ? (s / MICRO_SCALE) : (MICRO_SCALE / s);
+        this.microRatio = ur;
+        this.maxMicros = Long.MAX_VALUE / ur;
+        long mr = (s >= MILLI_SCALE) ? (s / MILLI_SCALE) : (MILLI_SCALE / s);
+        this.milliRatio = (int)mr;
+        this.maxMillis = Long.MAX_VALUE / mr;
+        long sr = (s >= SECOND_SCALE) ? (s / SECOND_SCALE) : (SECOND_SCALE / s);
+        this.secRatio = (int)sr;
+        this.maxSecs = Long.MAX_VALUE / sr;
+    }
+
+    /**
+     * General conversion utility.
+     *
+     * @param d duration
+     * @param dst result unit scale
+     * @param src source unit scale
+     */
+    private static long cvt(long d, long dst, long src) {
+        long r, m;
+        if (src == dst)
+            return d;
+        else if (src < dst)
+            return d / (dst / src);
+        else if (d > (m = Long.MAX_VALUE / (r = src / dst)))
+            return Long.MAX_VALUE;
+        else if (d < -m)
+            return Long.MIN_VALUE;
+        else
+            return d * r;
+    }
+
+    /**
+     * Converts the given time duration in the given unit to this unit.
+     * Conversions from finer to coarser granularities truncate, so
+     * lose precision. For example, converting {@code 999} milliseconds
+     * to seconds results in {@code 0}. Conversions from coarser to
+     * finer granularities with arguments that would numerically
+     * overflow saturate to {@code Long.MIN_VALUE} if negative or
+     * {@code Long.MAX_VALUE} if positive.
+     *
+     * <p>For example, to convert 10 minutes to milliseconds, use:
+     * {@code TimeUnit.MILLISECONDS.convert(10L, TimeUnit.MINUTES)}
+     *
+     * @param sourceDuration the time duration in the given {@code sourceUnit}
+     * @param sourceUnit the unit of the {@code sourceDuration} argument
+     * @return the converted duration in this unit,
+     * or {@code Long.MIN_VALUE} if conversion would negatively overflow,
+     * or {@code Long.MAX_VALUE} if it would positively overflow.
+     */
+    public long convert(long sourceDuration, TimeUnit sourceUnit) {
+        switch (this) {
+        case NANOSECONDS:  return sourceUnit.toNanos(sourceDuration);
+        case MICROSECONDS: return sourceUnit.toMicros(sourceDuration);
+        case MILLISECONDS: return sourceUnit.toMillis(sourceDuration);
+        case SECONDS:      return sourceUnit.toSeconds(sourceDuration);
+        default: return cvt(sourceDuration, scale, sourceUnit.scale);
+        }
+    }
+
+    /**
+     * Equivalent to
+     * {@link #convert(long, TimeUnit) NANOSECONDS.convert(duration, this)}.
+     * @param duration the duration
+     * @return the converted duration,
+     * or {@code Long.MIN_VALUE} if conversion would negatively overflow,
+     * or {@code Long.MAX_VALUE} if it would positively overflow.
+     */
+    public long toNanos(long duration) {
+        long s, m;
+        if ((s = scale) == NANO_SCALE)
+            return duration;
+        else if (duration > (m = maxNanos))
+            return Long.MAX_VALUE;
+        else if (duration < -m)
+            return Long.MIN_VALUE;
+        else
+            return duration * s;
+    }
+
+    /**
+     * Equivalent to
+     * {@link #convert(long, TimeUnit) MICROSECONDS.convert(duration, this)}.
+     * @param duration the duration
+     * @return the converted duration,
+     * or {@code Long.MIN_VALUE} if conversion would negatively overflow,
+     * or {@code Long.MAX_VALUE} if it would positively overflow.
+     */
+    public long toMicros(long duration) {
+        long s, m;
+        if ((s = scale) == MICRO_SCALE)
+            return duration;
+        else if (s < MICRO_SCALE)
+            return duration / microRatio;
+        else if (duration > (m = maxMicros))
+            return Long.MAX_VALUE;
+        else if (duration < -m)
+            return Long.MIN_VALUE;
+        else
+            return duration * microRatio;
+    }
+
+    /**
+     * Equivalent to
+     * {@link #convert(long, TimeUnit) MILLISECONDS.convert(duration, this)}.
+     * @param duration the duration
+     * @return the converted duration,
+     * or {@code Long.MIN_VALUE} if conversion would negatively overflow,
+     * or {@code Long.MAX_VALUE} if it would positively overflow.
+     */
+    public long toMillis(long duration) {
+        long s, m;
+        if ((s = scale) == MILLI_SCALE)
+            return duration;
+        else if (s < MILLI_SCALE)
+            return duration / milliRatio;
+        else if (duration > (m = maxMillis))
+            return Long.MAX_VALUE;
+        else if (duration < -m)
+            return Long.MIN_VALUE;
+        else
+            return duration * milliRatio;
+    }
+
+    /**
+     * Equivalent to
+     * {@link #convert(long, TimeUnit) SECONDS.convert(duration, this)}.
+     * @param duration the duration
+     * @return the converted duration,
+     * or {@code Long.MIN_VALUE} if conversion would negatively overflow,
+     * or {@code Long.MAX_VALUE} if it would positively overflow.
+     */
+    public long toSeconds(long duration) {
+        long s, m;
+        if ((s = scale) == SECOND_SCALE)
+            return duration;
+        else if (s < SECOND_SCALE)
+            return duration / secRatio;
+        else if (duration > (m = maxSecs))
+            return Long.MAX_VALUE;
+        else if (duration < -m)
+            return Long.MIN_VALUE;
+        else
+            return duration * secRatio;
+    }
+
+    /**
+     * Equivalent to
+     * {@link #convert(long, TimeUnit) MINUTES.convert(duration, this)}.
+     * @param duration the duration
+     * @return the converted duration,
+     * or {@code Long.MIN_VALUE} if conversion would negatively overflow,
+     * or {@code Long.MAX_VALUE} if it would positively overflow.
+     * @since 1.6
+     */
+    public long toMinutes(long duration) {
+        return cvt(duration, MINUTE_SCALE, scale);
+    }
+
+    /**
+     * Equivalent to
+     * {@link #convert(long, TimeUnit) HOURS.convert(duration, this)}.
+     * @param duration the duration
+     * @return the converted duration,
+     * or {@code Long.MIN_VALUE} if conversion would negatively overflow,
+     * or {@code Long.MAX_VALUE} if it would positively overflow.
+     * @since 1.6
+     */
+    public long toHours(long duration) {
+        return cvt(duration, HOUR_SCALE, scale);
+    }
+
+    /**
+     * Equivalent to
+     * {@link #convert(long, TimeUnit) DAYS.convert(duration, this)}.
+     * @param duration the duration
+     * @return the converted duration
+     * @since 1.6
+     */
+    public long toDays(long duration) {
+        return cvt(duration, DAY_SCALE, scale);
+    }
+
+    /**
+     * Utility to compute the excess-nanosecond argument to wait,
+     * sleep, join.
+     * @param d the duration
+     * @param m the number of milliseconds
+     * @return the number of nanoseconds
+     */
+    private int excessNanos(long d, long m) {
+        long s;
+        if ((s = scale) == NANO_SCALE)
+            return (int)(d - (m * MILLI_SCALE));
+        else if (s == MICRO_SCALE)
+            return (int)((d * 1000L) - (m * MILLI_SCALE));
+        else
+            return 0;
+    }
+
+    /**
+     * Performs a timed {@link Object#wait(long, int) Object.wait}
+     * using this time unit.
+     * This is a convenience method that converts timeout arguments
+     * into the form required by the {@code Object.wait} method.
+     *
+     * <p>For example, you could implement a blocking {@code poll} method
+     * (see {@link BlockingQueue#poll(long, TimeUnit) BlockingQueue.poll})
+     * using:
+     *
+     * <pre> {@code
+     * public synchronized Object poll(long timeout, TimeUnit unit)
+     *     throws InterruptedException {
+     *   while (empty) {
+     *     unit.timedWait(this, timeout);
+     *     ...
+     *   }
+     * }}</pre>
+     *
+     * @param obj the object to wait on
+     * @param timeout the maximum time to wait. If less than
+     * or equal to zero, do not wait at all.
+     * @throws InterruptedException if interrupted while waiting
+     */
+    public void timedWait(Object obj, long timeout)
+            throws InterruptedException {
+        if (timeout > 0) {
+            long ms = toMillis(timeout);
+            int ns = excessNanos(timeout, ms);
+            obj.wait(ms, ns);
+        }
+    }
+
+    /**
+     * Performs a timed {@link Thread#join(long, int) Thread.join}
+     * using this time unit.
+     * This is a convenience method that converts time arguments into the
+     * form required by the {@code Thread.join} method.
+     *
+     * @param thread the thread to wait for
+     * @param timeout the maximum time to wait. If less than
+     * or equal to zero, do not wait at all.
+     * @throws InterruptedException if interrupted while waiting
+     */
+    public void timedJoin(Thread thread, long timeout)
+            throws InterruptedException {
+        if (timeout > 0) {
+            long ms = toMillis(timeout);
+            int ns = excessNanos(timeout, ms);
+            thread.join(ms, ns);
+        }
+    }
+
+    /**
+     * Performs a {@link Thread#sleep(long, int) Thread.sleep} using
+     * this time unit.
+     * This is a convenience method that converts time arguments into the
+     * form required by the {@code Thread.sleep} method.
+     *
+     * @param timeout the minimum time to sleep. If less than
+     * or equal to zero, do not sleep at all.
+     * @throws InterruptedException if interrupted while sleeping
+     */
+    public void sleep(long timeout) throws InterruptedException {
+        if (timeout > 0) {
+            long ms = toMillis(timeout);
+            int ns = excessNanos(timeout, ms);
+            Thread.sleep(ms, ns);
+        }
+    }
+
+    /**
+     * Converts this {@code TimeUnit} to the equivalent {@code ChronoUnit}.
+     *
+     * @return the converted equivalent ChronoUnit
+     * @since 9
+     */
+    public ChronoUnit toChronoUnit() {
+        switch (this) {
+        case NANOSECONDS:  return ChronoUnit.NANOS;
+        case MICROSECONDS: return ChronoUnit.MICROS;
+        case MILLISECONDS: return ChronoUnit.MILLIS;
+        case SECONDS:      return ChronoUnit.SECONDS;
+        case MINUTES:      return ChronoUnit.MINUTES;
+        case HOURS:        return ChronoUnit.HOURS;
+        case DAYS:         return ChronoUnit.DAYS;
+        default: throw new AssertionError();
+        }
+    }
+
+    /**
+     * Converts a {@code ChronoUnit} to the equivalent {@code TimeUnit}.
+     *
+     * @param chronoUnit the ChronoUnit to convert
+     * @return the converted equivalent TimeUnit
+     * @throws IllegalArgumentException if {@code chronoUnit} has no
+     *         equivalent TimeUnit
+     * @throws NullPointerException if {@code chronoUnit} is null
+     * @since 9
+     */
+    public static TimeUnit of(ChronoUnit chronoUnit) {
+        switch (Objects.requireNonNull(chronoUnit, "chronoUnit")) {
+        case NANOS:   return TimeUnit.NANOSECONDS;
+        case MICROS:  return TimeUnit.MICROSECONDS;
+        case MILLIS:  return TimeUnit.MILLISECONDS;
+        case SECONDS: return TimeUnit.SECONDS;
+        case MINUTES: return TimeUnit.MINUTES;
+        case HOURS:   return TimeUnit.HOURS;
+        case DAYS:    return TimeUnit.DAYS;
+        default:
+            throw new IllegalArgumentException(
+                "No TimeUnit equivalent for " + chronoUnit);
+        }
+    }
+
+}

src/java.base/share/classes/java/util/concurrent/TimeoutException.java

@@ -0,0 +1,67 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent;
+
+/**
+ * Exception thrown when a blocking operation times out.  Blocking
+ * operations for which a timeout is specified need a means to
+ * indicate that the timeout has occurred. For many such operations it
+ * is possible to return a value that indicates timeout; when that is
+ * not possible or desirable then {@code TimeoutException} should be
+ * declared and thrown.
+ *
+ * @since 1.5
+ * @author Doug Lea
+ */
+public class TimeoutException extends Exception {
+    private static final long serialVersionUID = 1900926677490660714L;
+
+    /**
+     * Constructs a {@code TimeoutException} with no specified detail
+     * message.
+     */
+    public TimeoutException() {}
+
+    /**
+     * Constructs a {@code TimeoutException} with the specified detail
+     * message.
+     *
+     * @param message the detail message
+     */
+    public TimeoutException(String message) {
+        super(message);
+    }
+}

src/java.base/share/classes/java/util/concurrent/TransferQueue.java

@@ -0,0 +1,161 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent;
+
+/**
+ * A {@link BlockingQueue} in which producers may wait for consumers
+ * to receive elements.  A {@code TransferQueue} may be useful for
+ * example in message passing applications in which producers
+ * sometimes (using method {@link #transfer}) await receipt of
+ * elements by consumers invoking {@code take} or {@code poll}, while
+ * at other times enqueue elements (via method {@code put}) without
+ * waiting for receipt.
+ * {@linkplain #tryTransfer(Object) Non-blocking} and
+ * {@linkplain #tryTransfer(Object,long,TimeUnit) time-out} versions of
+ * {@code tryTransfer} are also available.
+ * A {@code TransferQueue} may also be queried, via {@link
+ * #hasWaitingConsumer}, whether there are any threads waiting for
+ * items, which is a converse analogy to a {@code peek} operation.
+ *
+ * <p>Like other blocking queues, a {@code TransferQueue} may be
+ * capacity bounded.  If so, an attempted transfer operation may
+ * initially block waiting for available space, and/or subsequently
+ * block waiting for reception by a consumer.  Note that in a queue
+ * with zero capacity, such as {@link SynchronousQueue}, {@code put}
+ * and {@code transfer} are effectively synonymous.
+ *
+ * <p>This interface is a member of the
+ * <a href="{@docRoot}/java/util/package-summary.html#CollectionsFramework">
+ * Java Collections Framework</a>.
+ *
+ * @since 1.7
+ * @author Doug Lea
+ * @param <E> the type of elements held in this queue
+ */
+public interface TransferQueue<E> extends BlockingQueue<E> {
+    /**
+     * Transfers the element to a waiting consumer immediately, if possible.
+     *
+     * <p>More precisely, transfers the specified element immediately
+     * if there exists a consumer already waiting to receive it (in
+     * {@link #take} or timed {@link #poll(long,TimeUnit) poll}),
+     * otherwise returning {@code false} without enqueuing the element.
+     *
+     * @param e the element to transfer
+     * @return {@code true} if the element was transferred, else
+     *         {@code false}
+     * @throws ClassCastException if the class of the specified element
+     *         prevents it from being added to this queue
+     * @throws NullPointerException if the specified element is null
+     * @throws IllegalArgumentException if some property of the specified
+     *         element prevents it from being added to this queue
+     */
+    boolean tryTransfer(E e);
+
+    /**
+     * Transfers the element to a consumer, waiting if necessary to do so.
+     *
+     * <p>More precisely, transfers the specified element immediately
+     * if there exists a consumer already waiting to receive it (in
+     * {@link #take} or timed {@link #poll(long,TimeUnit) poll}),
+     * else waits until the element is received by a consumer.
+     *
+     * @param e the element to transfer
+     * @throws InterruptedException if interrupted while waiting,
+     *         in which case the element is not left enqueued
+     * @throws ClassCastException if the class of the specified element
+     *         prevents it from being added to this queue
+     * @throws NullPointerException if the specified element is null
+     * @throws IllegalArgumentException if some property of the specified
+     *         element prevents it from being added to this queue
+     */
+    void transfer(E e) throws InterruptedException;
+
+    /**
+     * Transfers the element to a consumer if it is possible to do so
+     * before the timeout elapses.
+     *
+     * <p>More precisely, transfers the specified element immediately
+     * if there exists a consumer already waiting to receive it (in
+     * {@link #take} or timed {@link #poll(long,TimeUnit) poll}),
+     * else waits until the element is received by a consumer,
+     * returning {@code false} if the specified wait time elapses
+     * before the element can be transferred.
+     *
+     * @param e the element to transfer
+     * @param timeout how long to wait before giving up, in units of
+     *        {@code unit}
+     * @param unit a {@code TimeUnit} determining how to interpret the
+     *        {@code timeout} parameter
+     * @return {@code true} if successful, or {@code false} if
+     *         the specified waiting time elapses before completion,
+     *         in which case the element is not left enqueued
+     * @throws InterruptedException if interrupted while waiting,
+     *         in which case the element is not left enqueued
+     * @throws ClassCastException if the class of the specified element
+     *         prevents it from being added to this queue
+     * @throws NullPointerException if the specified element is null
+     * @throws IllegalArgumentException if some property of the specified
+     *         element prevents it from being added to this queue
+     */
+    boolean tryTransfer(E e, long timeout, TimeUnit unit)
+        throws InterruptedException;
+
+    /**
+     * Returns {@code true} if there is at least one consumer waiting
+     * to receive an element via {@link #take} or
+     * timed {@link #poll(long,TimeUnit) poll}.
+     * The return value represents a momentary state of affairs.
+     *
+     * @return {@code true} if there is at least one waiting consumer
+     */
+    boolean hasWaitingConsumer();
+
+    /**
+     * Returns an estimate of the number of consumers waiting to
+     * receive elements via {@link #take} or timed
+     * {@link #poll(long,TimeUnit) poll}.  The return value is an
+     * approximation of a momentary state of affairs, that may be
+     * inaccurate if consumers have completed or given up waiting.
+     * The value may be useful for monitoring and heuristics, but
+     * not for synchronization control.  Implementations of this
+     * method are likely to be noticeably slower than those for
+     * {@link #hasWaitingConsumer}.
+     *
+     * @return the number of consumers waiting to receive elements
+     */
+    int getWaitingConsumerCount();
+}

src/java.base/share/classes/java/util/concurrent/atomic/AtomicBoolean.java

@@ -0,0 +1,359 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent.atomic;
+
+import java.lang.invoke.MethodHandles;
+import java.lang.invoke.VarHandle;
+
+/**
+ * A {@code boolean} value that may be updated atomically. See the
+ * {@link VarHandle} specification for descriptions of the properties
+ * of atomic accesses. An {@code AtomicBoolean} is used in
+ * applications such as atomically updated flags, and cannot be used
+ * as a replacement for a {@link java.lang.Boolean}.
+ *
+ * @since 1.5
+ * @author Doug Lea
+ */
+public class AtomicBoolean implements java.io.Serializable {
+    private static final long serialVersionUID = 4654671469794556979L;
+    private static final VarHandle VALUE;
+    static {
+        try {
+            MethodHandles.Lookup l = MethodHandles.lookup();
+            VALUE = l.findVarHandle(AtomicBoolean.class, "value", int.class);
+        } catch (ReflectiveOperationException e) {
+            throw new Error(e);
+        }
+    }
+
+    private volatile int value;
+
+    /**
+     * Creates a new {@code AtomicBoolean} with the given initial value.
+     *
+     * @param initialValue the initial value
+     */
+    public AtomicBoolean(boolean initialValue) {
+        value = initialValue ? 1 : 0;
+    }
+
+    /**
+     * Creates a new {@code AtomicBoolean} with initial value {@code false}.
+     */
+    public AtomicBoolean() {
+    }
+
+    /**
+     * Returns the current value,
+     * with memory effects as specified by {@link VarHandle#getVolatile}.
+     *
+     * @return the current value
+     */
+    public final boolean get() {
+        return value != 0;
+    }
+
+    /**
+     * Atomically sets the value to {@code newValue}
+     * if the current value {@code == expectedValue},
+     * with memory effects as specified by {@link VarHandle#compareAndSet}.
+     *
+     * @param expectedValue the expected value
+     * @param newValue the new value
+     * @return {@code true} if successful. False return indicates that
+     * the actual value was not equal to the expected value.
+     */
+    public final boolean compareAndSet(boolean expectedValue, boolean newValue) {
+        return VALUE.compareAndSet(this,
+                                   (expectedValue ? 1 : 0),
+                                   (newValue ? 1 : 0));
+    }
+
+    /**
+     * Possibly atomically sets the value to {@code newValue}
+     * if the current value {@code == expectedValue},
+     * with memory effects as specified by {@link VarHandle#weakCompareAndSetPlain}.
+     *
+     * @deprecated This method has plain memory effects but the method
+     * name implies volatile memory effects (see methods such as
+     * {@link #compareAndExchange} and {@link #compareAndSet}).  To avoid
+     * confusion over plain or volatile memory effects it is recommended that
+     * the method {@link #weakCompareAndSetPlain} be used instead.
+     *
+     * @param expectedValue the expected value
+     * @param newValue the new value
+     * @return {@code true} if successful
+     * @see #weakCompareAndSetPlain
+     */
+    @Deprecated(since="9")
+    public boolean weakCompareAndSet(boolean expectedValue, boolean newValue) {
+        return VALUE.weakCompareAndSetPlain(this,
+                                            (expectedValue ? 1 : 0),
+                                            (newValue ? 1 : 0));
+    }
+
+    /**
+     * Possibly atomically sets the value to {@code newValue}
+     * if the current value {@code == expectedValue},
+     * with memory effects as specified by {@link VarHandle#weakCompareAndSetPlain}.
+     *
+     * @param expectedValue the expected value
+     * @param newValue the new value
+     * @return {@code true} if successful
+     * @since 9
+     */
+    public boolean weakCompareAndSetPlain(boolean expectedValue, boolean newValue) {
+        return VALUE.weakCompareAndSetPlain(this,
+                                            (expectedValue ? 1 : 0),
+                                            (newValue ? 1 : 0));
+    }
+
+    /**
+     * Sets the value to {@code newValue},
+     * with memory effects as specified by {@link VarHandle#setVolatile}.
+     *
+     * @param newValue the new value
+     */
+    public final void set(boolean newValue) {
+        value = newValue ? 1 : 0;
+    }
+
+    /**
+     * Sets the value to {@code newValue},
+     * with memory effects as specified by {@link VarHandle#setRelease}.
+     *
+     * @param newValue the new value
+     * @since 1.6
+     */
+    public final void lazySet(boolean newValue) {
+        VALUE.setRelease(this, (newValue ? 1 : 0));
+    }
+
+    /**
+     * Atomically sets the value to {@code newValue} and returns the old value,
+     * with memory effects as specified by {@link VarHandle#getAndSet}.
+     *
+     * @param newValue the new value
+     * @return the previous value
+     */
+    public final boolean getAndSet(boolean newValue) {
+        return (int)VALUE.getAndSet(this, (newValue ? 1 : 0)) != 0;
+    }
+
+    /**
+     * Returns the String representation of the current value.
+     * @return the String representation of the current value
+     */
+    public String toString() {
+        return Boolean.toString(get());
+    }
+
+    // jdk9
+
+    /**
+     * Returns the current value, with memory semantics of reading as
+     * if the variable was declared non-{@code volatile}.
+     *
+     * @return the value
+     * @since 9
+     */
+    public final boolean getPlain() {
+        return (int)VALUE.get(this) != 0;
+    }
+
+    /**
+     * Sets the value to {@code newValue}, with memory semantics
+     * of setting as if the variable was declared non-{@code volatile}
+     * and non-{@code final}.
+     *
+     * @param newValue the new value
+     * @since 9
+     */
+    public final void setPlain(boolean newValue) {
+        VALUE.set(this, newValue ? 1 : 0);
+    }
+
+    /**
+     * Returns the current value,
+     * with memory effects as specified by {@link VarHandle#getOpaque}.
+     *
+     * @return the value
+     * @since 9
+     */
+    public final boolean getOpaque() {
+        return (int)VALUE.getOpaque(this) != 0;
+    }
+
+    /**
+     * Sets the value to {@code newValue},
+     * with memory effects as specified by {@link VarHandle#setOpaque}.
+     *
+     * @param newValue the new value
+     * @since 9
+     */
+    public final void setOpaque(boolean newValue) {
+        VALUE.setOpaque(this, newValue ? 1 : 0);
+    }
+
+    /**
+     * Returns the current value,
+     * with memory effects as specified by {@link VarHandle#getAcquire}.
+     *
+     * @return the value
+     * @since 9
+     */
+    public final boolean getAcquire() {
+        return (int)VALUE.getAcquire(this) != 0;
+    }
+
+    /**
+     * Sets the value to {@code newValue},
+     * with memory effects as specified by {@link VarHandle#setRelease}.
+     *
+     * @param newValue the new value
+     * @since 9
+     */
+    public final void setRelease(boolean newValue) {
+        VALUE.setRelease(this, newValue ? 1 : 0);
+    }
+
+    /**
+     * Atomically sets the value to {@code newValue} if the current value,
+     * referred to as the <em>witness value</em>, {@code == expectedValue},
+     * with memory effects as specified by
+     * {@link VarHandle#compareAndExchange}.
+     *
+     * @param expectedValue the expected value
+     * @param newValue the new value
+     * @return the witness value, which will be the same as the
+     * expected value if successful
+     * @since 9
+     */
+    public final boolean compareAndExchange(boolean expectedValue, boolean newValue) {
+        return (int)VALUE.compareAndExchange(this,
+                                             (expectedValue ? 1 : 0),
+                                             (newValue ? 1 : 0)) != 0;
+    }
+
+    /**
+     * Atomically sets the value to {@code newValue} if the current value,
+     * referred to as the <em>witness value</em>, {@code == expectedValue},
+     * with memory effects as specified by
+     * {@link VarHandle#compareAndExchangeAcquire}.
+     *
+     * @param expectedValue the expected value
+     * @param newValue the new value
+     * @return the witness value, which will be the same as the
+     * expected value if successful
+     * @since 9
+     */
+    public final boolean compareAndExchangeAcquire(boolean expectedValue, boolean newValue) {
+        return (int)VALUE.compareAndExchangeAcquire(this,
+                                                    (expectedValue ? 1 : 0),
+                                                    (newValue ? 1 : 0)) != 0;
+    }
+
+    /**
+     * Atomically sets the value to {@code newValue} if the current value,
+     * referred to as the <em>witness value</em>, {@code == expectedValue},
+     * with memory effects as specified by
+     * {@link VarHandle#compareAndExchangeRelease}.
+     *
+     * @param expectedValue the expected value
+     * @param newValue the new value
+     * @return the witness value, which will be the same as the
+     * expected value if successful
+     * @since 9
+     */
+    public final boolean compareAndExchangeRelease(boolean expectedValue, boolean newValue) {
+        return (int)VALUE.compareAndExchangeRelease(this,
+                                                    (expectedValue ? 1 : 0),
+                                                    (newValue ? 1 : 0)) != 0;
+    }
+
+    /**
+     * Possibly atomically sets the value to {@code newValue} if the current
+     * value {@code == expectedValue},
+     * with memory effects as specified by
+     * {@link VarHandle#weakCompareAndSet}.
+     *
+     * @param expectedValue the expected value
+     * @param newValue the new value
+     * @return {@code true} if successful
+     * @since 9
+     */
+    public final boolean weakCompareAndSetVolatile(boolean expectedValue, boolean newValue) {
+        return VALUE.weakCompareAndSet(this,
+                                       (expectedValue ? 1 : 0),
+                                       (newValue ? 1 : 0));
+    }
+
+    /**
+     * Possibly atomically sets the value to {@code newValue} if the current
+     * value {@code == expectedValue},
+     * with memory effects as specified by
+     * {@link VarHandle#weakCompareAndSetAcquire}.
+     *
+     * @param expectedValue the expected value
+     * @param newValue the new value
+     * @return {@code true} if successful
+     * @since 9
+     */
+    public final boolean weakCompareAndSetAcquire(boolean expectedValue, boolean newValue) {
+        return VALUE.weakCompareAndSetAcquire(this,
+                                              (expectedValue ? 1 : 0),
+                                              (newValue ? 1 : 0));
+    }
+
+    /**
+     * Possibly atomically sets the value to {@code newValue} if the current
+     * value {@code == expectedValue},
+     * with memory effects as specified by
+     * {@link VarHandle#weakCompareAndSetRelease}.
+     *
+     * @param expectedValue the expected value
+     * @param newValue the new value
+     * @return {@code true} if successful
+     * @since 9
+     */
+    public final boolean weakCompareAndSetRelease(boolean expectedValue, boolean newValue) {
+        return VALUE.weakCompareAndSetRelease(this,
+                                              (expectedValue ? 1 : 0),
+                                              (newValue ? 1 : 0));
+    }
+
+}

src/java.base/share/classes/java/util/concurrent/atomic/AtomicInteger.java

@@ -0,0 +1,551 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent.atomic;
+
+import java.lang.invoke.VarHandle;
+import java.util.function.IntBinaryOperator;
+import java.util.function.IntUnaryOperator;
+
+/**
+ * An {@code int} value that may be updated atomically.  See the
+ * {@link VarHandle} specification for descriptions of the properties
+ * of atomic accesses. An {@code AtomicInteger} is used in
+ * applications such as atomically incremented counters, and cannot be
+ * used as a replacement for an {@link java.lang.Integer}. However,
+ * this class does extend {@code Number} to allow uniform access by
+ * tools and utilities that deal with numerically-based classes.
+ *
+ * @since 1.5
+ * @author Doug Lea
+ */
+public class AtomicInteger extends Number implements java.io.Serializable {
+    private static final long serialVersionUID = 6214790243416807050L;
+
+    /*
+     * This class intended to be implemented using VarHandles, but there
+     * are unresolved cyclic startup dependencies.
+     */
+    private static final jdk.internal.misc.Unsafe U = jdk.internal.misc.Unsafe.getUnsafe();
+    private static final long VALUE = U.objectFieldOffset(AtomicInteger.class, "value");
+
+    private volatile int value;
+
+    /**
+     * Creates a new AtomicInteger with the given initial value.
+     *
+     * @param initialValue the initial value
+     */
+    public AtomicInteger(int initialValue) {
+        value = initialValue;
+    }
+
+    /**
+     * Creates a new AtomicInteger with initial value {@code 0}.
+     */
+    public AtomicInteger() {
+    }
+
+    /**
+     * Returns the current value,
+     * with memory effects as specified by {@link VarHandle#getVolatile}.
+     *
+     * @return the current value
+     */
+    public final int get() {
+        return value;
+    }
+
+    /**
+     * Sets the value to {@code newValue},
+     * with memory effects as specified by {@link VarHandle#setVolatile}.
+     *
+     * @param newValue the new value
+     */
+    public final void set(int newValue) {
+        value = newValue;
+    }
+
+    /**
+     * Sets the value to {@code newValue},
+     * with memory effects as specified by {@link VarHandle#setRelease}.
+     *
+     * @param newValue the new value
+     * @since 1.6
+     */
+    public final void lazySet(int newValue) {
+        U.putIntRelease(this, VALUE, newValue);
+    }
+
+    /**
+     * Atomically sets the value to {@code newValue} and returns the old value,
+     * with memory effects as specified by {@link VarHandle#getAndSet}.
+     *
+     * @param newValue the new value
+     * @return the previous value
+     */
+    public final int getAndSet(int newValue) {
+        return U.getAndSetInt(this, VALUE, newValue);
+    }
+
+    /**
+     * Atomically sets the value to {@code newValue}
+     * if the current value {@code == expectedValue},
+     * with memory effects as specified by {@link VarHandle#compareAndSet}.
+     *
+     * @param expectedValue the expected value
+     * @param newValue the new value
+     * @return {@code true} if successful. False return indicates that
+     * the actual value was not equal to the expected value.
+     */
+    public final boolean compareAndSet(int expectedValue, int newValue) {
+        return U.compareAndSetInt(this, VALUE, expectedValue, newValue);
+    }
+
+    /**
+     * Possibly atomically sets the value to {@code newValue}
+     * if the current value {@code == expectedValue},
+     * with memory effects as specified by {@link VarHandle#weakCompareAndSetPlain}.
+     *
+     * @deprecated This method has plain memory effects but the method
+     * name implies volatile memory effects (see methods such as
+     * {@link #compareAndExchange} and {@link #compareAndSet}).  To avoid
+     * confusion over plain or volatile memory effects it is recommended that
+     * the method {@link #weakCompareAndSetPlain} be used instead.
+     *
+     * @param expectedValue the expected value
+     * @param newValue the new value
+     * @return {@code true} if successful
+     * @see #weakCompareAndSetPlain
+     */
+    @Deprecated(since="9")
+    public final boolean weakCompareAndSet(int expectedValue, int newValue) {
+        return U.weakCompareAndSetIntPlain(this, VALUE, expectedValue, newValue);
+    }
+
+    /**
+     * Possibly atomically sets the value to {@code newValue}
+     * if the current value {@code == expectedValue},
+     * with memory effects as specified by {@link VarHandle#weakCompareAndSetPlain}.
+     *
+     * @param expectedValue the expected value
+     * @param newValue the new value
+     * @return {@code true} if successful
+     * @since 9
+     */
+    public final boolean weakCompareAndSetPlain(int expectedValue, int newValue) {
+        return U.weakCompareAndSetIntPlain(this, VALUE, expectedValue, newValue);
+    }
+
+    /**
+     * Atomically increments the current value,
+     * with memory effects as specified by {@link VarHandle#getAndAdd}.
+     *
+     * <p>Equivalent to {@code getAndAdd(1)}.
+     *
+     * @return the previous value
+     */
+    public final int getAndIncrement() {
+        return U.getAndAddInt(this, VALUE, 1);
+    }
+
+    /**
+     * Atomically decrements the current value,
+     * with memory effects as specified by {@link VarHandle#getAndAdd}.
+     *
+     * <p>Equivalent to {@code getAndAdd(-1)}.
+     *
+     * @return the previous value
+     */
+    public final int getAndDecrement() {
+        return U.getAndAddInt(this, VALUE, -1);
+    }
+
+    /**
+     * Atomically adds the given value to the current value,
+     * with memory effects as specified by {@link VarHandle#getAndAdd}.
+     *
+     * @param delta the value to add
+     * @return the previous value
+     */
+    public final int getAndAdd(int delta) {
+        return U.getAndAddInt(this, VALUE, delta);
+    }
+
+    /**
+     * Atomically increments the current value,
+     * with memory effects as specified by {@link VarHandle#getAndAdd}.
+     *
+     * <p>Equivalent to {@code addAndGet(1)}.
+     *
+     * @return the updated value
+     */
+    public final int incrementAndGet() {
+        return U.getAndAddInt(this, VALUE, 1) + 1;
+    }
+
+    /**
+     * Atomically decrements the current value,
+     * with memory effects as specified by {@link VarHandle#getAndAdd}.
+     *
+     * <p>Equivalent to {@code addAndGet(-1)}.
+     *
+     * @return the updated value
+     */
+    public final int decrementAndGet() {
+        return U.getAndAddInt(this, VALUE, -1) - 1;
+    }
+
+    /**
+     * Atomically adds the given value to the current value,
+     * with memory effects as specified by {@link VarHandle#getAndAdd}.
+     *
+     * @param delta the value to add
+     * @return the updated value
+     */
+    public final int addAndGet(int delta) {
+        return U.getAndAddInt(this, VALUE, delta) + delta;
+    }
+
+    /**
+     * Atomically updates (with memory effects as specified by {@link
+     * VarHandle#compareAndSet}) the current value with the results of
+     * applying the given function, returning the previous value. The
+     * function should be side-effect-free, since it may be re-applied
+     * when attempted updates fail due to contention among threads.
+     *
+     * @param updateFunction a side-effect-free function
+     * @return the previous value
+     * @since 1.8
+     */
+    public final int getAndUpdate(IntUnaryOperator updateFunction) {
+        int prev = get(), next = 0;
+        for (boolean haveNext = false;;) {
+            if (!haveNext)
+                next = updateFunction.applyAsInt(prev);
+            if (weakCompareAndSetVolatile(prev, next))
+                return prev;
+            haveNext = (prev == (prev = get()));
+        }
+    }
+
+    /**
+     * Atomically updates (with memory effects as specified by {@link
+     * VarHandle#compareAndSet}) the current value with the results of
+     * applying the given function, returning the updated value. The
+     * function should be side-effect-free, since it may be re-applied
+     * when attempted updates fail due to contention among threads.
+     *
+     * @param updateFunction a side-effect-free function
+     * @return the updated value
+     * @since 1.8
+     */
+    public final int updateAndGet(IntUnaryOperator updateFunction) {
+        int prev = get(), next = 0;
+        for (boolean haveNext = false;;) {
+            if (!haveNext)
+                next = updateFunction.applyAsInt(prev);
+            if (weakCompareAndSetVolatile(prev, next))
+                return next;
+            haveNext = (prev == (prev = get()));
+        }
+    }
+
+    /**
+     * Atomically updates (with memory effects as specified by {@link
+     * VarHandle#compareAndSet}) the current value with the results of
+     * applying the given function to the current and given values,
+     * returning the previous value. The function should be
+     * side-effect-free, since it may be re-applied when attempted
+     * updates fail due to contention among threads.  The function is
+     * applied with the current value as its first argument, and the
+     * given update as the second argument.
+     *
+     * @param x the update value
+     * @param accumulatorFunction a side-effect-free function of two arguments
+     * @return the previous value
+     * @since 1.8
+     */
+    public final int getAndAccumulate(int x,
+                                      IntBinaryOperator accumulatorFunction) {
+        int prev = get(), next = 0;
+        for (boolean haveNext = false;;) {
+            if (!haveNext)
+                next = accumulatorFunction.applyAsInt(prev, x);
+            if (weakCompareAndSetVolatile(prev, next))
+                return prev;
+            haveNext = (prev == (prev = get()));
+        }
+    }
+
+    /**
+     * Atomically updates (with memory effects as specified by {@link
+     * VarHandle#compareAndSet}) the current value with the results of
+     * applying the given function to the current and given values,
+     * returning the updated value. The function should be
+     * side-effect-free, since it may be re-applied when attempted
+     * updates fail due to contention among threads.  The function is
+     * applied with the current value as its first argument, and the
+     * given update as the second argument.
+     *
+     * @param x the update value
+     * @param accumulatorFunction a side-effect-free function of two arguments
+     * @return the updated value
+     * @since 1.8
+     */
+    public final int accumulateAndGet(int x,
+                                      IntBinaryOperator accumulatorFunction) {
+        int prev = get(), next = 0;
+        for (boolean haveNext = false;;) {
+            if (!haveNext)
+                next = accumulatorFunction.applyAsInt(prev, x);
+            if (weakCompareAndSetVolatile(prev, next))
+                return next;
+            haveNext = (prev == (prev = get()));
+        }
+    }
+
+    /**
+     * Returns the String representation of the current value.
+     * @return the String representation of the current value
+     */
+    public String toString() {
+        return Integer.toString(get());
+    }
+
+    /**
+     * Returns the current value of this {@code AtomicInteger} as an
+     * {@code int},
+     * with memory effects as specified by {@link VarHandle#getVolatile}.
+     *
+     * Equivalent to {@link #get()}.
+     */
+    public int intValue() {
+        return get();
+    }
+
+    /**
+     * Returns the current value of this {@code AtomicInteger} as a
+     * {@code long} after a widening primitive conversion,
+     * with memory effects as specified by {@link VarHandle#getVolatile}.
+     * @jls 5.1.2 Widening Primitive Conversions
+     */
+    public long longValue() {
+        return (long)get();
+    }
+
+    /**
+     * Returns the current value of this {@code AtomicInteger} as a
+     * {@code float} after a widening primitive conversion,
+     * with memory effects as specified by {@link VarHandle#getVolatile}.
+     * @jls 5.1.2 Widening Primitive Conversions
+     */
+    public float floatValue() {
+        return (float)get();
+    }
+
+    /**
+     * Returns the current value of this {@code AtomicInteger} as a
+     * {@code double} after a widening primitive conversion,
+     * with memory effects as specified by {@link VarHandle#getVolatile}.
+     * @jls 5.1.2 Widening Primitive Conversions
+     */
+    public double doubleValue() {
+        return (double)get();
+    }
+
+    // jdk9
+
+    /**
+     * Returns the current value, with memory semantics of reading as
+     * if the variable was declared non-{@code volatile}.
+     *
+     * @return the value
+     * @since 9
+     */
+    public final int getPlain() {
+        return U.getInt(this, VALUE);
+    }
+
+    /**
+     * Sets the value to {@code newValue}, with memory semantics
+     * of setting as if the variable was declared non-{@code volatile}
+     * and non-{@code final}.
+     *
+     * @param newValue the new value
+     * @since 9
+     */
+    public final void setPlain(int newValue) {
+        U.putInt(this, VALUE, newValue);
+    }
+
+    /**
+     * Returns the current value,
+     * with memory effects as specified by {@link VarHandle#getOpaque}.
+     *
+     * @return the value
+     * @since 9
+     */
+    public final int getOpaque() {
+        return U.getIntOpaque(this, VALUE);
+    }
+
+    /**
+     * Sets the value to {@code newValue},
+     * with memory effects as specified by {@link VarHandle#setOpaque}.
+     *
+     * @param newValue the new value
+     * @since 9
+     */
+    public final void setOpaque(int newValue) {
+        U.putIntOpaque(this, VALUE, newValue);
+    }
+
+    /**
+     * Returns the current value,
+     * with memory effects as specified by {@link VarHandle#getAcquire}.
+     *
+     * @return the value
+     * @since 9
+     */
+    public final int getAcquire() {
+        return U.getIntAcquire(this, VALUE);
+    }
+
+    /**
+     * Sets the value to {@code newValue},
+     * with memory effects as specified by {@link VarHandle#setRelease}.
+     *
+     * @param newValue the new value
+     * @since 9
+     */
+    public final void setRelease(int newValue) {
+        U.putIntRelease(this, VALUE, newValue);
+    }
+
+    /**
+     * Atomically sets the value to {@code newValue} if the current value,
+     * referred to as the <em>witness value</em>, {@code == expectedValue},
+     * with memory effects as specified by
+     * {@link VarHandle#compareAndExchange}.
+     *
+     * @param expectedValue the expected value
+     * @param newValue the new value
+     * @return the witness value, which will be the same as the
+     * expected value if successful
+     * @since 9
+     */
+    public final int compareAndExchange(int expectedValue, int newValue) {
+        return U.compareAndExchangeInt(this, VALUE, expectedValue, newValue);
+    }
+
+    /**
+     * Atomically sets the value to {@code newValue} if the current value,
+     * referred to as the <em>witness value</em>, {@code == expectedValue},
+     * with memory effects as specified by
+     * {@link VarHandle#compareAndExchangeAcquire}.
+     *
+     * @param expectedValue the expected value
+     * @param newValue the new value
+     * @return the witness value, which will be the same as the
+     * expected value if successful
+     * @since 9
+     */
+    public final int compareAndExchangeAcquire(int expectedValue, int newValue) {
+        return U.compareAndExchangeIntAcquire(this, VALUE, expectedValue, newValue);
+    }
+
+    /**
+     * Atomically sets the value to {@code newValue} if the current value,
+     * referred to as the <em>witness value</em>, {@code == expectedValue},
+     * with memory effects as specified by
+     * {@link VarHandle#compareAndExchangeRelease}.
+     *
+     * @param expectedValue the expected value
+     * @param newValue the new value
+     * @return the witness value, which will be the same as the
+     * expected value if successful
+     * @since 9
+     */
+    public final int compareAndExchangeRelease(int expectedValue, int newValue) {
+        return U.compareAndExchangeIntRelease(this, VALUE, expectedValue, newValue);
+    }
+
+    /**
+     * Possibly atomically sets the value to {@code newValue} if
+     * the current value {@code == expectedValue},
+     * with memory effects as specified by
+     * {@link VarHandle#weakCompareAndSet}.
+     *
+     * @param expectedValue the expected value
+     * @param newValue the new value
+     * @return {@code true} if successful
+     * @since 9
+     */
+    public final boolean weakCompareAndSetVolatile(int expectedValue, int newValue) {
+        return U.weakCompareAndSetInt(this, VALUE, expectedValue, newValue);
+    }
+
+    /**
+     * Possibly atomically sets the value to {@code newValue} if
+     * the current value {@code == expectedValue},
+     * with memory effects as specified by
+     * {@link VarHandle#weakCompareAndSetAcquire}.
+     *
+     * @param expectedValue the expected value
+     * @param newValue the new value
+     * @return {@code true} if successful
+     * @since 9
+     */
+    public final boolean weakCompareAndSetAcquire(int expectedValue, int newValue) {
+        return U.weakCompareAndSetIntAcquire(this, VALUE, expectedValue, newValue);
+    }
+
+    /**
+     * Possibly atomically sets the value to {@code newValue} if
+     * the current value {@code == expectedValue},
+     * with memory effects as specified by
+     * {@link VarHandle#weakCompareAndSetRelease}.
+     *
+     * @param expectedValue the expected value
+     * @param newValue the new value
+     * @return {@code true} if successful
+     * @since 9
+     */
+    public final boolean weakCompareAndSetRelease(int expectedValue, int newValue) {
+        return U.weakCompareAndSetIntRelease(this, VALUE, expectedValue, newValue);
+    }
+
+}

src/java.base/share/classes/java/util/concurrent/atomic/AtomicIntegerArray.java

@@ -0,0 +1,566 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent.atomic;
+
+import java.lang.invoke.MethodHandles;
+import java.lang.invoke.VarHandle;
+import java.util.function.IntBinaryOperator;
+import java.util.function.IntUnaryOperator;
+
+/**
+ * An {@code int} array in which elements may be updated atomically.
+ * See the {@link VarHandle} specification for descriptions of the
+ * properties of atomic accesses.
+ * @since 1.5
+ * @author Doug Lea
+ */
+public class AtomicIntegerArray implements java.io.Serializable {
+    private static final long serialVersionUID = 2862133569453604235L;
+    private static final VarHandle AA
+        = MethodHandles.arrayElementVarHandle(int[].class);
+    private final int[] array;
+
+    /**
+     * Creates a new AtomicIntegerArray of the given length, with all
+     * elements initially zero.
+     *
+     * @param length the length of the array
+     */
+    public AtomicIntegerArray(int length) {
+        array = new int[length];
+    }
+
+    /**
+     * Creates a new AtomicIntegerArray with the same length as, and
+     * all elements copied from, the given array.
+     *
+     * @param array the array to copy elements from
+     * @throws NullPointerException if array is null
+     */
+    public AtomicIntegerArray(int[] array) {
+        // Visibility guaranteed by final field guarantees
+        this.array = array.clone();
+    }
+
+    /**
+     * Returns the length of the array.
+     *
+     * @return the length of the array
+     */
+    public final int length() {
+        return array.length;
+    }
+
+    /**
+     * Returns the current value of the element at index {@code i},
+     * with memory effects as specified by {@link VarHandle#getVolatile}.
+     *
+     * @param i the index
+     * @return the current value
+     */
+    public final int get(int i) {
+        return (int)AA.getVolatile(array, i);
+    }
+
+    /**
+     * Sets the element at index {@code i} to {@code newValue},
+     * with memory effects as specified by {@link VarHandle#setVolatile}.
+     *
+     * @param i the index
+     * @param newValue the new value
+     */
+    public final void set(int i, int newValue) {
+        AA.setVolatile(array, i, newValue);
+    }
+
+    /**
+     * Sets the element at index {@code i} to {@code newValue},
+     * with memory effects as specified by {@link VarHandle#setRelease}.
+     *
+     * @param i the index
+     * @param newValue the new value
+     * @since 1.6
+     */
+    public final void lazySet(int i, int newValue) {
+        AA.setRelease(array, i, newValue);
+    }
+
+    /**
+     * Atomically sets the element at index {@code i} to {@code
+     * newValue} and returns the old value,
+     * with memory effects as specified by {@link VarHandle#getAndSet}.
+     *
+     * @param i the index
+     * @param newValue the new value
+     * @return the previous value
+     */
+    public final int getAndSet(int i, int newValue) {
+        return (int)AA.getAndSet(array, i, newValue);
+    }
+
+    /**
+     * Atomically sets the element at index {@code i} to {@code
+     * newValue} if the element's current value {@code == expectedValue},
+     * with memory effects as specified by {@link VarHandle#compareAndSet}.
+     *
+     * @param i the index
+     * @param expectedValue the expected value
+     * @param newValue the new value
+     * @return {@code true} if successful. False return indicates that
+     * the actual value was not equal to the expected value.
+     */
+    public final boolean compareAndSet(int i, int expectedValue, int newValue) {
+        return AA.compareAndSet(array, i, expectedValue, newValue);
+    }
+
+    /**
+     * Possibly atomically sets the element at index {@code i} to
+     * {@code newValue} if the element's current value {@code == expectedValue},
+     * with memory effects as specified by {@link VarHandle#weakCompareAndSetPlain}.
+     *
+     * @deprecated This method has plain memory effects but the method
+     * name implies volatile memory effects (see methods such as
+     * {@link #compareAndExchange} and {@link #compareAndSet}).  To avoid
+     * confusion over plain or volatile memory effects it is recommended that
+     * the method {@link #weakCompareAndSetPlain} be used instead.
+     *
+     * @param i the index
+     * @param expectedValue the expected value
+     * @param newValue the new value
+     * @return {@code true} if successful
+     * @see #weakCompareAndSetPlain
+     */
+    @Deprecated(since="9")
+    public final boolean weakCompareAndSet(int i, int expectedValue, int newValue) {
+        return AA.weakCompareAndSetPlain(array, i, expectedValue, newValue);
+    }
+
+    /**
+     * Possibly atomically sets the element at index {@code i} to
+     * {@code newValue} if the element's current value {@code == expectedValue},
+     * with memory effects as specified by {@link VarHandle#weakCompareAndSetPlain}.
+     *
+     * @param i the index
+     * @param expectedValue the expected value
+     * @param newValue the new value
+     * @return {@code true} if successful
+     * @since 9
+     */
+    public final boolean weakCompareAndSetPlain(int i, int expectedValue, int newValue) {
+        return AA.weakCompareAndSetPlain(array, i, expectedValue, newValue);
+    }
+
+    /**
+     * Atomically increments the value of the element at index {@code i},
+     * with memory effects as specified by {@link VarHandle#getAndAdd}.
+     *
+     * <p>Equivalent to {@code getAndAdd(i, 1)}.
+     *
+     * @param i the index
+     * @return the previous value
+     */
+    public final int getAndIncrement(int i) {
+        return (int)AA.getAndAdd(array, i, 1);
+    }
+
+    /**
+     * Atomically decrements the value of the element at index {@code i},
+     * with memory effects as specified by {@link VarHandle#getAndAdd}.
+     *
+     * <p>Equivalent to {@code getAndAdd(i, -1)}.
+     *
+     * @param i the index
+     * @return the previous value
+     */
+    public final int getAndDecrement(int i) {
+        return (int)AA.getAndAdd(array, i, -1);
+    }
+
+    /**
+     * Atomically adds the given value to the element at index {@code i},
+     * with memory effects as specified by {@link VarHandle#getAndAdd}.
+     *
+     * @param i the index
+     * @param delta the value to add
+     * @return the previous value
+     */
+    public final int getAndAdd(int i, int delta) {
+        return (int)AA.getAndAdd(array, i, delta);
+    }
+
+    /**
+     * Atomically increments the value of the element at index {@code i},
+     * with memory effects as specified by {@link VarHandle#getAndAdd}.
+     *
+     * <p>Equivalent to {@code addAndGet(i, 1)}.
+     *
+     * @param i the index
+     * @return the updated value
+     */
+    public final int incrementAndGet(int i) {
+        return (int)AA.getAndAdd(array, i, 1) + 1;
+    }
+
+    /**
+     * Atomically decrements the value of the element at index {@code i},
+     * with memory effects as specified by {@link VarHandle#getAndAdd}.
+     *
+     * <p>Equivalent to {@code addAndGet(i, -1)}.
+     *
+     * @param i the index
+     * @return the updated value
+     */
+    public final int decrementAndGet(int i) {
+        return (int)AA.getAndAdd(array, i, -1) - 1;
+    }
+
+    /**
+     * Atomically adds the given value to the element at index {@code i},
+     * with memory effects as specified by {@link VarHandle#getAndAdd}.
+     *
+     * @param i the index
+     * @param delta the value to add
+     * @return the updated value
+     */
+    public final int addAndGet(int i, int delta) {
+        return (int)AA.getAndAdd(array, i, delta) + delta;
+    }
+
+    /**
+     * Atomically updates (with memory effects as specified by {@link
+     * VarHandle#compareAndSet}) the element at index {@code i} with
+     * the results of applying the given function, returning the
+     * previous value. The function should be side-effect-free, since
+     * it may be re-applied when attempted updates fail due to
+     * contention among threads.
+     *
+     * @param i the index
+     * @param updateFunction a side-effect-free function
+     * @return the previous value
+     * @since 1.8
+     */
+    public final int getAndUpdate(int i, IntUnaryOperator updateFunction) {
+        int prev = get(i), next = 0;
+        for (boolean haveNext = false;;) {
+            if (!haveNext)
+                next = updateFunction.applyAsInt(prev);
+            if (weakCompareAndSetVolatile(i, prev, next))
+                return prev;
+            haveNext = (prev == (prev = get(i)));
+        }
+    }
+
+    /**
+     * Atomically updates (with memory effects as specified by {@link
+     * VarHandle#compareAndSet}) the element at index {@code i} with
+     * the results of applying the given function, returning the
+     * updated value. The function should be side-effect-free, since it
+     * may be re-applied when attempted updates fail due to contention
+     * among threads.
+     *
+     * @param i the index
+     * @param updateFunction a side-effect-free function
+     * @return the updated value
+     * @since 1.8
+     */
+    public final int updateAndGet(int i, IntUnaryOperator updateFunction) {
+        int prev = get(i), next = 0;
+        for (boolean haveNext = false;;) {
+            if (!haveNext)
+                next = updateFunction.applyAsInt(prev);
+            if (weakCompareAndSetVolatile(i, prev, next))
+                return next;
+            haveNext = (prev == (prev = get(i)));
+        }
+    }
+
+    /**
+     * Atomically updates (with memory effects as specified by {@link
+     * VarHandle#compareAndSet}) the element at index {@code i} with
+     * the results of applying the given function to the current and
+     * given values, returning the previous value. The function should
+     * be side-effect-free, since it may be re-applied when attempted
+     * updates fail due to contention among threads.  The function is
+     * applied with the current value of the element at index {@code i}
+     * as its first argument, and the given update as the second
+     * argument.
+     *
+     * @param i the index
+     * @param x the update value
+     * @param accumulatorFunction a side-effect-free function of two arguments
+     * @return the previous value
+     * @since 1.8
+     */
+    public final int getAndAccumulate(int i, int x,
+                                      IntBinaryOperator accumulatorFunction) {
+        int prev = get(i), next = 0;
+        for (boolean haveNext = false;;) {
+            if (!haveNext)
+                next = accumulatorFunction.applyAsInt(prev, x);
+            if (weakCompareAndSetVolatile(i, prev, next))
+                return prev;
+            haveNext = (prev == (prev = get(i)));
+        }
+    }
+
+    /**
+     * Atomically updates (with memory effects as specified by {@link
+     * VarHandle#compareAndSet}) the element at index {@code i} with
+     * the results of applying the given function to the current and
+     * given values, returning the updated value. The function should
+     * be side-effect-free, since it may be re-applied when attempted
+     * updates fail due to contention among threads.  The function is
+     * applied with the current value of the element at index {@code i}
+     * as its first argument, and the given update as the second
+     * argument.
+     *
+     * @param i the index
+     * @param x the update value
+     * @param accumulatorFunction a side-effect-free function of two arguments
+     * @return the updated value
+     * @since 1.8
+     */
+    public final int accumulateAndGet(int i, int x,
+                                      IntBinaryOperator accumulatorFunction) {
+        int prev = get(i), next = 0;
+        for (boolean haveNext = false;;) {
+            if (!haveNext)
+                next = accumulatorFunction.applyAsInt(prev, x);
+            if (weakCompareAndSetVolatile(i, prev, next))
+                return next;
+            haveNext = (prev == (prev = get(i)));
+        }
+    }
+
+    /**
+     * Returns the String representation of the current values of array.
+     * @return the String representation of the current values of array
+     */
+    public String toString() {
+        int iMax = array.length - 1;
+        if (iMax == -1)
+            return "[]";
+
+        StringBuilder b = new StringBuilder();
+        b.append('[');
+        for (int i = 0; ; i++) {
+            b.append(get(i));
+            if (i == iMax)
+                return b.append(']').toString();
+            b.append(',').append(' ');
+        }
+    }
+
+    // jdk9
+
+    /**
+     * Returns the current value of the element at index {@code i},
+     * with memory semantics of reading as if the variable was declared
+     * non-{@code volatile}.
+     *
+     * @param i the index
+     * @return the value
+     * @since 9
+     */
+    public final int getPlain(int i) {
+        return (int)AA.get(array, i);
+    }
+
+    /**
+     * Sets the element at index {@code i} to {@code newValue},
+     * with memory semantics of setting as if the variable was
+     * declared non-{@code volatile} and non-{@code final}.
+     *
+     * @param i the index
+     * @param newValue the new value
+     * @since 9
+     */
+    public final void setPlain(int i, int newValue) {
+        AA.set(array, i, newValue);
+    }
+
+    /**
+     * Returns the current value of the element at index {@code i},
+     * with memory effects as specified by {@link VarHandle#getOpaque}.
+     *
+     * @param i the index
+     * @return the value
+     * @since 9
+     */
+    public final int getOpaque(int i) {
+        return (int)AA.getOpaque(array, i);
+    }
+
+    /**
+     * Sets the element at index {@code i} to {@code newValue},
+     * with memory effects as specified by {@link VarHandle#setOpaque}.
+     *
+     * @param i the index
+     * @param newValue the new value
+     * @since 9
+     */
+    public final void setOpaque(int i, int newValue) {
+        AA.setOpaque(array, i, newValue);
+    }
+
+    /**
+     * Returns the current value of the element at index {@code i},
+     * with memory effects as specified by {@link VarHandle#getAcquire}.
+     *
+     * @param i the index
+     * @return the value
+     * @since 9
+     */
+    public final int getAcquire(int i) {
+        return (int)AA.getAcquire(array, i);
+    }
+
+    /**
+     * Sets the element at index {@code i} to {@code newValue},
+     * with memory effects as specified by {@link VarHandle#setRelease}.
+     *
+     * @param i the index
+     * @param newValue the new value
+     * @since 9
+     */
+    public final void setRelease(int i, int newValue) {
+        AA.setRelease(array, i, newValue);
+    }
+
+    /**
+     * Atomically sets the element at index {@code i} to {@code newValue}
+     * if the element's current value, referred to as the <em>witness
+     * value</em>, {@code == expectedValue},
+     * with memory effects as specified by
+     * {@link VarHandle#compareAndExchange}.
+     *
+     * @param i the index
+     * @param expectedValue the expected value
+     * @param newValue the new value
+     * @return the witness value, which will be the same as the
+     * expected value if successful
+     * @since 9
+     */
+    public final int compareAndExchange(int i, int expectedValue, int newValue) {
+        return (int)AA.compareAndExchange(array, i, expectedValue, newValue);
+    }
+
+    /**
+     * Atomically sets the element at index {@code i} to {@code newValue}
+     * if the element's current value, referred to as the <em>witness
+     * value</em>, {@code == expectedValue},
+     * with memory effects as specified by
+     * {@link VarHandle#compareAndExchangeAcquire}.
+     *
+     * @param i the index
+     * @param expectedValue the expected value
+     * @param newValue the new value
+     * @return the witness value, which will be the same as the
+     * expected value if successful
+     * @since 9
+     */
+    public final int compareAndExchangeAcquire(int i, int expectedValue, int newValue) {
+        return (int)AA.compareAndExchangeAcquire(array, i, expectedValue, newValue);
+    }
+
+    /**
+     * Atomically sets the element at index {@code i} to {@code newValue}
+     * if the element's current value, referred to as the <em>witness
+     * value</em>, {@code == expectedValue},
+     * with memory effects as specified by
+     * {@link VarHandle#compareAndExchangeRelease}.
+     *
+     * @param i the index
+     * @param expectedValue the expected value
+     * @param newValue the new value
+     * @return the witness value, which will be the same as the
+     * expected value if successful
+     * @since 9
+     */
+    public final int compareAndExchangeRelease(int i, int expectedValue, int newValue) {
+        return (int)AA.compareAndExchangeRelease(array, i, expectedValue, newValue);
+    }
+
+    /**
+     * Possibly atomically sets the element at index {@code i} to
+     * {@code newValue} if the element's current value {@code == expectedValue},
+     * with memory effects as specified by
+     * {@link VarHandle#weakCompareAndSet}.
+     *
+     * @param i the index
+     * @param expectedValue the expected value
+     * @param newValue the new value
+     * @return {@code true} if successful
+     * @since 9
+     */
+    public final boolean weakCompareAndSetVolatile(int i, int expectedValue, int newValue) {
+        return AA.weakCompareAndSet(array, i, expectedValue, newValue);
+    }
+
+    /**
+     * Possibly atomically sets the element at index {@code i} to
+     * {@code newValue} if the element's current value {@code == expectedValue},
+     * with memory effects as specified by
+     * {@link VarHandle#weakCompareAndSetAcquire}.
+     *
+     * @param i the index
+     * @param expectedValue the expected value
+     * @param newValue the new value
+     * @return {@code true} if successful
+     * @since 9
+     */
+    public final boolean weakCompareAndSetAcquire(int i, int expectedValue, int newValue) {
+        return AA.weakCompareAndSetAcquire(array, i, expectedValue, newValue);
+    }
+
+    /**
+     * Possibly atomically sets the element at index {@code i} to
+     * {@code newValue} if the element's current value {@code == expectedValue},
+     * with memory effects as specified by
+     * {@link VarHandle#weakCompareAndSetRelease}.
+     *
+     * @param i the index
+     * @param expectedValue the expected value
+     * @param newValue the new value
+     * @return {@code true} if successful
+     * @since 9
+     */
+    public final boolean weakCompareAndSetRelease(int i, int expectedValue, int newValue) {
+        return AA.weakCompareAndSetRelease(array, i, expectedValue, newValue);
+    }
+
+
+}

src/java.base/share/classes/java/util/concurrent/atomic/AtomicIntegerFieldUpdater.java

@@ -0,0 +1,545 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent.atomic;
+
+import java.lang.reflect.Field;
+import java.lang.reflect.Modifier;
+import java.security.AccessController;
+import java.security.PrivilegedActionException;
+import java.security.PrivilegedExceptionAction;
+import java.util.Objects;
+import java.util.function.IntBinaryOperator;
+import java.util.function.IntUnaryOperator;
+import jdk.internal.misc.Unsafe;
+import jdk.internal.reflect.CallerSensitive;
+import jdk.internal.reflect.Reflection;
+import java.lang.invoke.VarHandle;
+
+/**
+ * A reflection-based utility that enables atomic updates to
+ * designated {@code volatile int} fields of designated classes.
+ * This class is designed for use in atomic data structures in which
+ * several fields of the same node are independently subject to atomic
+ * updates.
+ *
+ * <p>Note that the guarantees of the {@code compareAndSet}
+ * method in this class are weaker than in other atomic classes.
+ * Because this class cannot ensure that all uses of the field
+ * are appropriate for purposes of atomic access, it can
+ * guarantee atomicity only with respect to other invocations of
+ * {@code compareAndSet} and {@code set} on the same updater.
+ *
+ * <p>Object arguments for parameters of type {@code T} that are not
+ * instances of the class passed to {@link #newUpdater} will result in
+ * a {@link ClassCastException} being thrown.
+ *
+ * @since 1.5
+ * @author Doug Lea
+ * @param <T> The type of the object holding the updatable field
+ */
+public abstract class AtomicIntegerFieldUpdater<T> {
+    /**
+     * Creates and returns an updater for objects with the given field.
+     * The Class argument is needed to check that reflective types and
+     * generic types match.
+     *
+     * @param tclass the class of the objects holding the field
+     * @param fieldName the name of the field to be updated
+     * @param <U> the type of instances of tclass
+     * @return the updater
+     * @throws IllegalArgumentException if the field is not a
+     * volatile integer type
+     * @throws RuntimeException with a nested reflection-based
+     * exception if the class does not hold field or is the wrong type,
+     * or the field is inaccessible to the caller according to Java language
+     * access control
+     */
+    @CallerSensitive
+    public static <U> AtomicIntegerFieldUpdater<U> newUpdater(Class<U> tclass,
+                                                              String fieldName) {
+        return new AtomicIntegerFieldUpdaterImpl<U>
+            (tclass, fieldName, Reflection.getCallerClass());
+    }
+
+    /**
+     * Protected do-nothing constructor for use by subclasses.
+     */
+    protected AtomicIntegerFieldUpdater() {
+    }
+
+    /**
+     * Atomically sets the field of the given object managed by this updater
+     * to the given updated value if the current value {@code ==} the
+     * expected value. This method is guaranteed to be atomic with respect to
+     * other calls to {@code compareAndSet} and {@code set}, but not
+     * necessarily with respect to other changes in the field.
+     *
+     * @param obj An object whose field to conditionally set
+     * @param expect the expected value
+     * @param update the new value
+     * @return {@code true} if successful
+     */
+    public abstract boolean compareAndSet(T obj, int expect, int update);
+
+    /**
+     * Atomically sets the field of the given object managed by this updater
+     * to the given updated value if the current value {@code ==} the
+     * expected value. This method is guaranteed to be atomic with respect to
+     * other calls to {@code compareAndSet} and {@code set}, but not
+     * necessarily with respect to other changes in the field.
+     *
+     * <p><a href="package-summary.html#weakCompareAndSet">May fail
+     * spuriously and does not provide ordering guarantees</a>, so is
+     * only rarely an appropriate alternative to {@code compareAndSet}.
+     *
+     * @param obj An object whose field to conditionally set
+     * @param expect the expected value
+     * @param update the new value
+     * @return {@code true} if successful
+     */
+    public abstract boolean weakCompareAndSet(T obj, int expect, int update);
+
+    /**
+     * Sets the field of the given object managed by this updater to the
+     * given updated value. This operation is guaranteed to act as a volatile
+     * store with respect to subsequent invocations of {@code compareAndSet}.
+     *
+     * @param obj An object whose field to set
+     * @param newValue the new value
+     */
+    public abstract void set(T obj, int newValue);
+
+    /**
+     * Eventually sets the field of the given object managed by this
+     * updater to the given updated value.
+     *
+     * @param obj An object whose field to set
+     * @param newValue the new value
+     * @since 1.6
+     */
+    public abstract void lazySet(T obj, int newValue);
+
+    /**
+     * Returns the current value held in the field of the given object
+     * managed by this updater.
+     *
+     * @param obj An object whose field to get
+     * @return the current value
+     */
+    public abstract int get(T obj);
+
+    /**
+     * Atomically sets the field of the given object managed by this updater
+     * to the given value and returns the old value.
+     *
+     * @param obj An object whose field to get and set
+     * @param newValue the new value
+     * @return the previous value
+     */
+    public int getAndSet(T obj, int newValue) {
+        int prev;
+        do {
+            prev = get(obj);
+        } while (!compareAndSet(obj, prev, newValue));
+        return prev;
+    }
+
+    /**
+     * Atomically increments by one the current value of the field of the
+     * given object managed by this updater.
+     *
+     * @param obj An object whose field to get and set
+     * @return the previous value
+     */
+    public int getAndIncrement(T obj) {
+        int prev, next;
+        do {
+            prev = get(obj);
+            next = prev + 1;
+        } while (!compareAndSet(obj, prev, next));
+        return prev;
+    }
+
+    /**
+     * Atomically decrements by one the current value of the field of the
+     * given object managed by this updater.
+     *
+     * @param obj An object whose field to get and set
+     * @return the previous value
+     */
+    public int getAndDecrement(T obj) {
+        int prev, next;
+        do {
+            prev = get(obj);
+            next = prev - 1;
+        } while (!compareAndSet(obj, prev, next));
+        return prev;
+    }
+
+    /**
+     * Atomically adds the given value to the current value of the field of
+     * the given object managed by this updater.
+     *
+     * @param obj An object whose field to get and set
+     * @param delta the value to add
+     * @return the previous value
+     */
+    public int getAndAdd(T obj, int delta) {
+        int prev, next;
+        do {
+            prev = get(obj);
+            next = prev + delta;
+        } while (!compareAndSet(obj, prev, next));
+        return prev;
+    }
+
+    /**
+     * Atomically increments by one the current value of the field of the
+     * given object managed by this updater.
+     *
+     * @param obj An object whose field to get and set
+     * @return the updated value
+     */
+    public int incrementAndGet(T obj) {
+        int prev, next;
+        do {
+            prev = get(obj);
+            next = prev + 1;
+        } while (!compareAndSet(obj, prev, next));
+        return next;
+    }
+
+    /**
+     * Atomically decrements by one the current value of the field of the
+     * given object managed by this updater.
+     *
+     * @param obj An object whose field to get and set
+     * @return the updated value
+     */
+    public int decrementAndGet(T obj) {
+        int prev, next;
+        do {
+            prev = get(obj);
+            next = prev - 1;
+        } while (!compareAndSet(obj, prev, next));
+        return next;
+    }
+
+    /**
+     * Atomically adds the given value to the current value of the field of
+     * the given object managed by this updater.
+     *
+     * @param obj An object whose field to get and set
+     * @param delta the value to add
+     * @return the updated value
+     */
+    public int addAndGet(T obj, int delta) {
+        int prev, next;
+        do {
+            prev = get(obj);
+            next = prev + delta;
+        } while (!compareAndSet(obj, prev, next));
+        return next;
+    }
+
+    /**
+     * Atomically updates (with memory effects as specified by {@link
+     * VarHandle#compareAndSet}) the field of the given object managed
+     * by this updater with the results of applying the given
+     * function, returning the previous value. The function should be
+     * side-effect-free, since it may be re-applied when attempted
+     * updates fail due to contention among threads.
+     *
+     * @param obj An object whose field to get and set
+     * @param updateFunction a side-effect-free function
+     * @return the previous value
+     * @since 1.8
+     */
+    public final int getAndUpdate(T obj, IntUnaryOperator updateFunction) {
+        int prev, next;
+        do {
+            prev = get(obj);
+            next = updateFunction.applyAsInt(prev);
+        } while (!compareAndSet(obj, prev, next));
+        return prev;
+    }
+
+    /**
+     * Atomically updates (with memory effects as specified by {@link
+     * VarHandle#compareAndSet}) the field of the given object managed
+     * by this updater with the results of applying the given
+     * function, returning the updated value. The function should be
+     * side-effect-free, since it may be re-applied when attempted
+     * updates fail due to contention among threads.
+     *
+     * @param obj An object whose field to get and set
+     * @param updateFunction a side-effect-free function
+     * @return the updated value
+     * @since 1.8
+     */
+    public final int updateAndGet(T obj, IntUnaryOperator updateFunction) {
+        int prev, next;
+        do {
+            prev = get(obj);
+            next = updateFunction.applyAsInt(prev);
+        } while (!compareAndSet(obj, prev, next));
+        return next;
+    }
+
+    /**
+     * Atomically updates (with memory effects as specified by {@link
+     * VarHandle#compareAndSet}) the field of the given object managed
+     * by this updater with the results of applying the given function
+     * to the current and given values, returning the previous value.
+     * The function should be side-effect-free, since it may be
+     * re-applied when attempted updates fail due to contention among
+     * threads.  The function is applied with the current value as its
+     * first argument, and the given update as the second argument.
+     *
+     * @param obj An object whose field to get and set
+     * @param x the update value
+     * @param accumulatorFunction a side-effect-free function of two arguments
+     * @return the previous value
+     * @since 1.8
+     */
+    public final int getAndAccumulate(T obj, int x,
+                                      IntBinaryOperator accumulatorFunction) {
+        int prev, next;
+        do {
+            prev = get(obj);
+            next = accumulatorFunction.applyAsInt(prev, x);
+        } while (!compareAndSet(obj, prev, next));
+        return prev;
+    }
+
+    /**
+     * Atomically updates (with memory effects as specified by {@link
+     * VarHandle#compareAndSet}) the field of the given object managed
+     * by this updater with the results of applying the given function
+     * to the current and given values, returning the updated value.
+     * The function should be side-effect-free, since it may be
+     * re-applied when attempted updates fail due to contention among
+     * threads.  The function is applied with the current value as its
+     * first argument, and the given update as the second argument.
+     *
+     * @param obj An object whose field to get and set
+     * @param x the update value
+     * @param accumulatorFunction a side-effect-free function of two arguments
+     * @return the updated value
+     * @since 1.8
+     */
+    public final int accumulateAndGet(T obj, int x,
+                                      IntBinaryOperator accumulatorFunction) {
+        int prev, next;
+        do {
+            prev = get(obj);
+            next = accumulatorFunction.applyAsInt(prev, x);
+        } while (!compareAndSet(obj, prev, next));
+        return next;
+    }
+
+    /**
+     * Standard hotspot implementation using intrinsics.
+     */
+    private static final class AtomicIntegerFieldUpdaterImpl<T>
+        extends AtomicIntegerFieldUpdater<T> {
+        private static final Unsafe U = Unsafe.getUnsafe();
+        private final long offset;
+        /**
+         * if field is protected, the subclass constructing updater, else
+         * the same as tclass
+         */
+        private final Class<?> cclass;
+        /** class holding the field */
+        private final Class<T> tclass;
+
+        AtomicIntegerFieldUpdaterImpl(final Class<T> tclass,
+                                      final String fieldName,
+                                      final Class<?> caller) {
+            final Field field;
+            final int modifiers;
+            try {
+                field = AccessController.doPrivileged(
+                    new PrivilegedExceptionAction<Field>() {
+                        public Field run() throws NoSuchFieldException {
+                            return tclass.getDeclaredField(fieldName);
+                        }
+                    });
+                modifiers = field.getModifiers();
+                sun.reflect.misc.ReflectUtil.ensureMemberAccess(
+                    caller, tclass, null, modifiers);
+                ClassLoader cl = tclass.getClassLoader();
+                ClassLoader ccl = caller.getClassLoader();
+                if ((ccl != null) && (ccl != cl) &&
+                    ((cl == null) || !isAncestor(cl, ccl))) {
+                    sun.reflect.misc.ReflectUtil.checkPackageAccess(tclass);
+                }
+            } catch (PrivilegedActionException pae) {
+                throw new RuntimeException(pae.getException());
+            } catch (Exception ex) {
+                throw new RuntimeException(ex);
+            }
+
+            if (field.getType() != int.class)
+                throw new IllegalArgumentException("Must be integer type");
+
+            if (!Modifier.isVolatile(modifiers))
+                throw new IllegalArgumentException("Must be volatile type");
+
+            // Access to protected field members is restricted to receivers only
+            // of the accessing class, or one of its subclasses, and the
+            // accessing class must in turn be a subclass (or package sibling)
+            // of the protected member's defining class.
+            // If the updater refers to a protected field of a declaring class
+            // outside the current package, the receiver argument will be
+            // narrowed to the type of the accessing class.
+            this.cclass = (Modifier.isProtected(modifiers) &&
+                           tclass.isAssignableFrom(caller) &&
+                           !isSamePackage(tclass, caller))
+                          ? caller : tclass;
+            this.tclass = tclass;
+            this.offset = U.objectFieldOffset(field);
+        }
+
+        /**
+         * Returns true if the second classloader can be found in the first
+         * classloader's delegation chain.
+         * Equivalent to the inaccessible: first.isAncestor(second).
+         */
+        private static boolean isAncestor(ClassLoader first, ClassLoader second) {
+            ClassLoader acl = first;
+            do {
+                acl = acl.getParent();
+                if (second == acl) {
+                    return true;
+                }
+            } while (acl != null);
+            return false;
+        }
+
+        /**
+         * Returns true if the two classes have the same class loader and
+         * package qualifier
+         */
+        private static boolean isSamePackage(Class<?> class1, Class<?> class2) {
+            return class1.getClassLoader() == class2.getClassLoader()
+                   && Objects.equals(class1.getPackageName(), class2.getPackageName());
+        }
+
+        /**
+         * Checks that target argument is instance of cclass.  On
+         * failure, throws cause.
+         */
+        private final void accessCheck(T obj) {
+            if (!cclass.isInstance(obj))
+                throwAccessCheckException(obj);
+        }
+
+        /**
+         * Throws access exception if accessCheck failed due to
+         * protected access, else ClassCastException.
+         */
+        private final void throwAccessCheckException(T obj) {
+            if (cclass == tclass)
+                throw new ClassCastException();
+            else
+                throw new RuntimeException(
+                    new IllegalAccessException(
+                        "Class " +
+                        cclass.getName() +
+                        " can not access a protected member of class " +
+                        tclass.getName() +
+                        " using an instance of " +
+                        obj.getClass().getName()));
+        }
+
+        public final boolean compareAndSet(T obj, int expect, int update) {
+            accessCheck(obj);
+            return U.compareAndSetInt(obj, offset, expect, update);
+        }
+
+        public final boolean weakCompareAndSet(T obj, int expect, int update) {
+            accessCheck(obj);
+            return U.compareAndSetInt(obj, offset, expect, update);
+        }
+
+        public final void set(T obj, int newValue) {
+            accessCheck(obj);
+            U.putIntVolatile(obj, offset, newValue);
+        }
+
+        public final void lazySet(T obj, int newValue) {
+            accessCheck(obj);
+            U.putIntRelease(obj, offset, newValue);
+        }
+
+        public final int get(T obj) {
+            accessCheck(obj);
+            return U.getIntVolatile(obj, offset);
+        }
+
+        public final int getAndSet(T obj, int newValue) {
+            accessCheck(obj);
+            return U.getAndSetInt(obj, offset, newValue);
+        }
+
+        public final int getAndAdd(T obj, int delta) {
+            accessCheck(obj);
+            return U.getAndAddInt(obj, offset, delta);
+        }
+
+        public final int getAndIncrement(T obj) {
+            return getAndAdd(obj, 1);
+        }
+
+        public final int getAndDecrement(T obj) {
+            return getAndAdd(obj, -1);
+        }
+
+        public final int incrementAndGet(T obj) {
+            return getAndAdd(obj, 1) + 1;
+        }
+
+        public final int decrementAndGet(T obj) {
+            return getAndAdd(obj, -1) - 1;
+        }
+
+        public final int addAndGet(T obj, int delta) {
+            return getAndAdd(obj, delta) + delta;
+        }
+
+    }
+}

src/java.base/share/classes/java/util/concurrent/atomic/AtomicLong.java

@@ -0,0 +1,564 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent.atomic;
+
+import java.lang.invoke.VarHandle;
+import java.util.function.LongBinaryOperator;
+import java.util.function.LongUnaryOperator;
+
+/**
+ * A {@code long} value that may be updated atomically.  See the
+ * {@link VarHandle} specification for descriptions of the properties
+ * of atomic accesses. An {@code AtomicLong} is used in applications
+ * such as atomically incremented sequence numbers, and cannot be used
+ * as a replacement for a {@link java.lang.Long}. However, this class
+ * does extend {@code Number} to allow uniform access by tools and
+ * utilities that deal with numerically-based classes.
+ *
+ * @since 1.5
+ * @author Doug Lea
+ */
+public class AtomicLong extends Number implements java.io.Serializable {
+    private static final long serialVersionUID = 1927816293512124184L;
+
+    /**
+     * Records whether the underlying JVM supports lockless
+     * compareAndSet for longs. While the intrinsic compareAndSetLong
+     * method works in either case, some constructions should be
+     * handled at Java level to avoid locking user-visible locks.
+     */
+    static final boolean VM_SUPPORTS_LONG_CAS = VMSupportsCS8();
+
+    /**
+     * Returns whether underlying JVM supports lockless CompareAndSet
+     * for longs. Called only once and cached in VM_SUPPORTS_LONG_CAS.
+     */
+    private static native boolean VMSupportsCS8();
+
+    /*
+     * This class intended to be implemented using VarHandles, but there
+     * are unresolved cyclic startup dependencies.
+     */
+    private static final jdk.internal.misc.Unsafe U = jdk.internal.misc.Unsafe.getUnsafe();
+    private static final long VALUE = U.objectFieldOffset(AtomicLong.class, "value");
+
+    private volatile long value;
+
+    /**
+     * Creates a new AtomicLong with the given initial value.
+     *
+     * @param initialValue the initial value
+     */
+    public AtomicLong(long initialValue) {
+        value = initialValue;
+    }
+
+    /**
+     * Creates a new AtomicLong with initial value {@code 0}.
+     */
+    public AtomicLong() {
+    }
+
+    /**
+     * Returns the current value,
+     * with memory effects as specified by {@link VarHandle#getVolatile}.
+     *
+     * @return the current value
+     */
+    public final long get() {
+        return value;
+    }
+
+    /**
+     * Sets the value to {@code newValue},
+     * with memory effects as specified by {@link VarHandle#setVolatile}.
+     *
+     * @param newValue the new value
+     */
+    public final void set(long newValue) {
+        // See JDK-8180620: Clarify VarHandle mixed-access subtleties
+        U.putLongVolatile(this, VALUE, newValue);
+    }
+
+    /**
+     * Sets the value to {@code newValue},
+     * with memory effects as specified by {@link VarHandle#setRelease}.
+     *
+     * @param newValue the new value
+     * @since 1.6
+     */
+    public final void lazySet(long newValue) {
+        U.putLongRelease(this, VALUE, newValue);
+    }
+
+    /**
+     * Atomically sets the value to {@code newValue} and returns the old value,
+     * with memory effects as specified by {@link VarHandle#getAndSet}.
+     *
+     * @param newValue the new value
+     * @return the previous value
+     */
+    public final long getAndSet(long newValue) {
+        return U.getAndSetLong(this, VALUE, newValue);
+    }
+
+    /**
+     * Atomically sets the value to {@code newValue}
+     * if the current value {@code == expectedValue},
+     * with memory effects as specified by {@link VarHandle#compareAndSet}.
+     *
+     * @param expectedValue the expected value
+     * @param newValue the new value
+     * @return {@code true} if successful. False return indicates that
+     * the actual value was not equal to the expected value.
+     */
+    public final boolean compareAndSet(long expectedValue, long newValue) {
+        return U.compareAndSetLong(this, VALUE, expectedValue, newValue);
+    }
+
+    /**
+     * Possibly atomically sets the value to {@code newValue}
+     * if the current value {@code == expectedValue},
+     * with memory effects as specified by {@link VarHandle#weakCompareAndSetPlain}.
+     *
+     * @deprecated This method has plain memory effects but the method
+     * name implies volatile memory effects (see methods such as
+     * {@link #compareAndExchange} and {@link #compareAndSet}).  To avoid
+     * confusion over plain or volatile memory effects it is recommended that
+     * the method {@link #weakCompareAndSetPlain} be used instead.
+     *
+     * @param expectedValue the expected value
+     * @param newValue the new value
+     * @return {@code true} if successful
+     * @see #weakCompareAndSetPlain
+     */
+    @Deprecated(since="9")
+    public final boolean weakCompareAndSet(long expectedValue, long newValue) {
+        return U.weakCompareAndSetLongPlain(this, VALUE, expectedValue, newValue);
+    }
+
+    /**
+     * Possibly atomically sets the value to {@code newValue}
+     * if the current value {@code == expectedValue},
+     * with memory effects as specified by {@link VarHandle#weakCompareAndSetPlain}.
+     *
+     * @param expectedValue the expected value
+     * @param newValue the new value
+     * @return {@code true} if successful
+     * @since 9
+     */
+    public final boolean weakCompareAndSetPlain(long expectedValue, long newValue) {
+        return U.weakCompareAndSetLongPlain(this, VALUE, expectedValue, newValue);
+    }
+
+    /**
+     * Atomically increments the current value,
+     * with memory effects as specified by {@link VarHandle#getAndAdd}.
+     *
+     * <p>Equivalent to {@code getAndAdd(1)}.
+     *
+     * @return the previous value
+     */
+    public final long getAndIncrement() {
+        return U.getAndAddLong(this, VALUE, 1L);
+    }
+
+    /**
+     * Atomically decrements the current value,
+     * with memory effects as specified by {@link VarHandle#getAndAdd}.
+     *
+     * <p>Equivalent to {@code getAndAdd(-1)}.
+     *
+     * @return the previous value
+     */
+    public final long getAndDecrement() {
+        return U.getAndAddLong(this, VALUE, -1L);
+    }
+
+    /**
+     * Atomically adds the given value to the current value,
+     * with memory effects as specified by {@link VarHandle#getAndAdd}.
+     *
+     * @param delta the value to add
+     * @return the previous value
+     */
+    public final long getAndAdd(long delta) {
+        return U.getAndAddLong(this, VALUE, delta);
+    }
+
+    /**
+     * Atomically increments the current value,
+     * with memory effects as specified by {@link VarHandle#getAndAdd}.
+     *
+     * <p>Equivalent to {@code addAndGet(1)}.
+     *
+     * @return the updated value
+     */
+    public final long incrementAndGet() {
+        return U.getAndAddLong(this, VALUE, 1L) + 1L;
+    }
+
+    /**
+     * Atomically decrements the current value,
+     * with memory effects as specified by {@link VarHandle#getAndAdd}.
+     *
+     * <p>Equivalent to {@code addAndGet(-1)}.
+     *
+     * @return the updated value
+     */
+    public final long decrementAndGet() {
+        return U.getAndAddLong(this, VALUE, -1L) - 1L;
+    }
+
+    /**
+     * Atomically adds the given value to the current value,
+     * with memory effects as specified by {@link VarHandle#getAndAdd}.
+     *
+     * @param delta the value to add
+     * @return the updated value
+     */
+    public final long addAndGet(long delta) {
+        return U.getAndAddLong(this, VALUE, delta) + delta;
+    }
+
+    /**
+     * Atomically updates (with memory effects as specified by {@link
+     * VarHandle#compareAndSet}) the current value with the results of
+     * applying the given function, returning the previous value. The
+     * function should be side-effect-free, since it may be re-applied
+     * when attempted updates fail due to contention among threads.
+     *
+     * @param updateFunction a side-effect-free function
+     * @return the previous value
+     * @since 1.8
+     */
+    public final long getAndUpdate(LongUnaryOperator updateFunction) {
+        long prev = get(), next = 0L;
+        for (boolean haveNext = false;;) {
+            if (!haveNext)
+                next = updateFunction.applyAsLong(prev);
+            if (weakCompareAndSetVolatile(prev, next))
+                return prev;
+            haveNext = (prev == (prev = get()));
+        }
+    }
+
+    /**
+     * Atomically updates (with memory effects as specified by {@link
+     * VarHandle#compareAndSet}) the current value with the results of
+     * applying the given function, returning the updated value. The
+     * function should be side-effect-free, since it may be re-applied
+     * when attempted updates fail due to contention among threads.
+     *
+     * @param updateFunction a side-effect-free function
+     * @return the updated value
+     * @since 1.8
+     */
+    public final long updateAndGet(LongUnaryOperator updateFunction) {
+        long prev = get(), next = 0L;
+        for (boolean haveNext = false;;) {
+            if (!haveNext)
+                next = updateFunction.applyAsLong(prev);
+            if (weakCompareAndSetVolatile(prev, next))
+                return next;
+            haveNext = (prev == (prev = get()));
+        }
+    }
+
+    /**
+     * Atomically updates (with memory effects as specified by {@link
+     * VarHandle#compareAndSet}) the current value with the results of
+     * applying the given function to the current and given values,
+     * returning the previous value. The function should be
+     * side-effect-free, since it may be re-applied when attempted
+     * updates fail due to contention among threads.  The function is
+     * applied with the current value as its first argument, and the
+     * given update as the second argument.
+     *
+     * @param x the update value
+     * @param accumulatorFunction a side-effect-free function of two arguments
+     * @return the previous value
+     * @since 1.8
+     */
+    public final long getAndAccumulate(long x,
+                                       LongBinaryOperator accumulatorFunction) {
+        long prev = get(), next = 0L;
+        for (boolean haveNext = false;;) {
+            if (!haveNext)
+                next = accumulatorFunction.applyAsLong(prev, x);
+            if (weakCompareAndSetVolatile(prev, next))
+                return prev;
+            haveNext = (prev == (prev = get()));
+        }
+    }
+
+    /**
+     * Atomically updates (with memory effects as specified by {@link
+     * VarHandle#compareAndSet}) the current value with the results of
+     * applying the given function to the current and given values,
+     * returning the updated value. The function should be
+     * side-effect-free, since it may be re-applied when attempted
+     * updates fail due to contention among threads.  The function is
+     * applied with the current value as its first argument, and the
+     * given update as the second argument.
+     *
+     * @param x the update value
+     * @param accumulatorFunction a side-effect-free function of two arguments
+     * @return the updated value
+     * @since 1.8
+     */
+    public final long accumulateAndGet(long x,
+                                       LongBinaryOperator accumulatorFunction) {
+        long prev = get(), next = 0L;
+        for (boolean haveNext = false;;) {
+            if (!haveNext)
+                next = accumulatorFunction.applyAsLong(prev, x);
+            if (weakCompareAndSetVolatile(prev, next))
+                return next;
+            haveNext = (prev == (prev = get()));
+        }
+    }
+
+    /**
+     * Returns the String representation of the current value.
+     * @return the String representation of the current value
+     */
+    public String toString() {
+        return Long.toString(get());
+    }
+
+    /**
+     * Returns the current value of this {@code AtomicLong} as an {@code int}
+     * after a narrowing primitive conversion,
+     * with memory effects as specified by {@link VarHandle#getVolatile}.
+     * @jls 5.1.3 Narrowing Primitive Conversions
+     */
+    public int intValue() {
+        return (int)get();
+    }
+
+    /**
+     * Returns the current value of this {@code AtomicLong} as a {@code long},
+     * with memory effects as specified by {@link VarHandle#getVolatile}.
+     * Equivalent to {@link #get()}.
+     */
+    public long longValue() {
+        return get();
+    }
+
+    /**
+     * Returns the current value of this {@code AtomicLong} as a {@code float}
+     * after a widening primitive conversion,
+     * with memory effects as specified by {@link VarHandle#getVolatile}.
+     * @jls 5.1.2 Widening Primitive Conversions
+     */
+    public float floatValue() {
+        return (float)get();
+    }
+
+    /**
+     * Returns the current value of this {@code AtomicLong} as a {@code double}
+     * after a widening primitive conversion,
+     * with memory effects as specified by {@link VarHandle#getVolatile}.
+     * @jls 5.1.2 Widening Primitive Conversions
+     */
+    public double doubleValue() {
+        return (double)get();
+    }
+
+    // jdk9
+
+    /**
+     * Returns the current value, with memory semantics of reading as if the
+     * variable was declared non-{@code volatile}.
+     *
+     * @return the value
+     * @since 9
+     */
+    public final long getPlain() {
+        return U.getLong(this, VALUE);
+    }
+
+    /**
+     * Sets the value to {@code newValue}, with memory semantics
+     * of setting as if the variable was declared non-{@code volatile}
+     * and non-{@code final}.
+     *
+     * @param newValue the new value
+     * @since 9
+     */
+    public final void setPlain(long newValue) {
+        U.putLong(this, VALUE, newValue);
+    }
+
+    /**
+     * Returns the current value,
+     * with memory effects as specified by {@link VarHandle#getOpaque}.
+     *
+     * @return the value
+     * @since 9
+     */
+    public final long getOpaque() {
+        return U.getLongOpaque(this, VALUE);
+    }
+
+    /**
+     * Sets the value to {@code newValue},
+     * with memory effects as specified by {@link VarHandle#setOpaque}.
+     *
+     * @param newValue the new value
+     * @since 9
+     */
+    public final void setOpaque(long newValue) {
+        U.putLongOpaque(this, VALUE, newValue);
+    }
+
+    /**
+     * Returns the current value,
+     * with memory effects as specified by {@link VarHandle#getAcquire}.
+     *
+     * @return the value
+     * @since 9
+     */
+    public final long getAcquire() {
+        return U.getLongAcquire(this, VALUE);
+    }
+
+    /**
+     * Sets the value to {@code newValue},
+     * with memory effects as specified by {@link VarHandle#setRelease}.
+     *
+     * @param newValue the new value
+     * @since 9
+     */
+    public final void setRelease(long newValue) {
+        U.putLongRelease(this, VALUE, newValue);
+    }
+
+    /**
+     * Atomically sets the value to {@code newValue} if the current value,
+     * referred to as the <em>witness value</em>, {@code == expectedValue},
+     * with memory effects as specified by
+     * {@link VarHandle#compareAndExchange}.
+     *
+     * @param expectedValue the expected value
+     * @param newValue the new value
+     * @return the witness value, which will be the same as the
+     * expected value if successful
+     * @since 9
+     */
+    public final long compareAndExchange(long expectedValue, long newValue) {
+        return U.compareAndExchangeLong(this, VALUE, expectedValue, newValue);
+    }
+
+    /**
+     * Atomically sets the value to {@code newValue} if the current value,
+     * referred to as the <em>witness value</em>, {@code == expectedValue},
+     * with memory effects as specified by
+     * {@link VarHandle#compareAndExchangeAcquire}.
+     *
+     * @param expectedValue the expected value
+     * @param newValue the new value
+     * @return the witness value, which will be the same as the
+     * expected value if successful
+     * @since 9
+     */
+    public final long compareAndExchangeAcquire(long expectedValue, long newValue) {
+        return U.compareAndExchangeLongAcquire(this, VALUE, expectedValue, newValue);
+    }
+
+    /**
+     * Atomically sets the value to {@code newValue} if the current value,
+     * referred to as the <em>witness value</em>, {@code == expectedValue},
+     * with memory effects as specified by
+     * {@link VarHandle#compareAndExchangeRelease}.
+     *
+     * @param expectedValue the expected value
+     * @param newValue the new value
+     * @return the witness value, which will be the same as the
+     * expected value if successful
+     * @since 9
+     */
+    public final long compareAndExchangeRelease(long expectedValue, long newValue) {
+        return U.compareAndExchangeLongRelease(this, VALUE, expectedValue, newValue);
+    }
+
+    /**
+     * Possibly atomically sets the value to {@code newValue}
+     * if the current value {@code == expectedValue},
+     * with memory effects as specified by
+     * {@link VarHandle#weakCompareAndSet}.
+     *
+     * @param expectedValue the expected value
+     * @param newValue the new value
+     * @return {@code true} if successful
+     * @since 9
+     */
+    public final boolean weakCompareAndSetVolatile(long expectedValue, long newValue) {
+        return U.weakCompareAndSetLong(this, VALUE, expectedValue, newValue);
+    }
+
+    /**
+     * Possibly atomically sets the value to {@code newValue}
+     * if the current value {@code == expectedValue},
+     * with memory effects as specified by
+     * {@link VarHandle#weakCompareAndSetAcquire}.
+     *
+     * @param expectedValue the expected value
+     * @param newValue the new value
+     * @return {@code true} if successful
+     * @since 9
+     */
+    public final boolean weakCompareAndSetAcquire(long expectedValue, long newValue) {
+        return U.weakCompareAndSetLongAcquire(this, VALUE, expectedValue, newValue);
+    }
+
+    /**
+     * Possibly atomically sets the value to {@code newValue}
+     * if the current value {@code == expectedValue},
+     * with memory effects as specified by
+     * {@link VarHandle#weakCompareAndSetRelease}.
+     *
+     * @param expectedValue the expected value
+     * @param newValue the new value
+     * @return {@code true} if successful
+     * @since 9
+     */
+    public final boolean weakCompareAndSetRelease(long expectedValue, long newValue) {
+        return U.weakCompareAndSetLongRelease(this, VALUE, expectedValue, newValue);
+    }
+
+}

src/java.base/share/classes/java/util/concurrent/atomic/AtomicLongArray.java

@@ -0,0 +1,565 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent.atomic;
+
+import java.lang.invoke.MethodHandles;
+import java.lang.invoke.VarHandle;
+import java.util.function.LongBinaryOperator;
+import java.util.function.LongUnaryOperator;
+
+/**
+ * A {@code long} array in which elements may be updated atomically.
+ * See the {@link VarHandle} specification for descriptions of the
+ * properties of atomic accesses.
+ * @since 1.5
+ * @author Doug Lea
+ */
+public class AtomicLongArray implements java.io.Serializable {
+    private static final long serialVersionUID = -2308431214976778248L;
+    private static final VarHandle AA
+        = MethodHandles.arrayElementVarHandle(long[].class);
+    private final long[] array;
+
+    /**
+     * Creates a new AtomicLongArray of the given length, with all
+     * elements initially zero.
+     *
+     * @param length the length of the array
+     */
+    public AtomicLongArray(int length) {
+        array = new long[length];
+    }
+
+    /**
+     * Creates a new AtomicLongArray with the same length as, and
+     * all elements copied from, the given array.
+     *
+     * @param array the array to copy elements from
+     * @throws NullPointerException if array is null
+     */
+    public AtomicLongArray(long[] array) {
+        // Visibility guaranteed by final field guarantees
+        this.array = array.clone();
+    }
+
+    /**
+     * Returns the length of the array.
+     *
+     * @return the length of the array
+     */
+    public final int length() {
+        return array.length;
+    }
+
+    /**
+     * Returns the current value of the element at index {@code i},
+     * with memory effects as specified by {@link VarHandle#getVolatile}.
+     *
+     * @param i the index
+     * @return the current value
+     */
+    public final long get(int i) {
+        return (long)AA.getVolatile(array, i);
+    }
+
+    /**
+     * Sets the element at index {@code i} to {@code newValue},
+     * with memory effects as specified by {@link VarHandle#setVolatile}.
+     *
+     * @param i the index
+     * @param newValue the new value
+     */
+    public final void set(int i, long newValue) {
+        AA.setVolatile(array, i, newValue);
+    }
+
+    /**
+     * Sets the element at index {@code i} to {@code newValue},
+     * with memory effects as specified by {@link VarHandle#setRelease}.
+     *
+     * @param i the index
+     * @param newValue the new value
+     * @since 1.6
+     */
+    public final void lazySet(int i, long newValue) {
+        AA.setRelease(array, i, newValue);
+    }
+
+    /**
+     * Atomically sets the element at index {@code i} to {@code
+     * newValue} and returns the old value,
+     * with memory effects as specified by {@link VarHandle#getAndSet}.
+     *
+     * @param i the index
+     * @param newValue the new value
+     * @return the previous value
+     */
+    public final long getAndSet(int i, long newValue) {
+        return (long)AA.getAndSet(array, i, newValue);
+    }
+
+    /**
+     * Atomically sets the element at index {@code i} to {@code newValue}
+     * if the element's current value {@code == expectedValue},
+     * with memory effects as specified by {@link VarHandle#compareAndSet}.
+     *
+     * @param i the index
+     * @param expectedValue the expected value
+     * @param newValue the new value
+     * @return {@code true} if successful. False return indicates that
+     * the actual value was not equal to the expected value.
+     */
+    public final boolean compareAndSet(int i, long expectedValue, long newValue) {
+        return AA.compareAndSet(array, i, expectedValue, newValue);
+    }
+
+    /**
+     * Possibly atomically sets the element at index {@code i} to
+     * {@code newValue} if the element's current value {@code == expectedValue},
+     * with memory effects as specified by {@link VarHandle#weakCompareAndSetPlain}.
+     *
+     * @deprecated This method has plain memory effects but the method
+     * name implies volatile memory effects (see methods such as
+     * {@link #compareAndExchange} and {@link #compareAndSet}).  To avoid
+     * confusion over plain or volatile memory effects it is recommended that
+     * the method {@link #weakCompareAndSetPlain} be used instead.
+     *
+     * @param i the index
+     * @param expectedValue the expected value
+     * @param newValue the new value
+     * @return {@code true} if successful
+     * @see #weakCompareAndSetPlain
+     */
+    @Deprecated(since="9")
+    public final boolean weakCompareAndSet(int i, long expectedValue, long newValue) {
+        return AA.weakCompareAndSetPlain(array, i, expectedValue, newValue);
+    }
+
+    /**
+     * Possibly atomically sets the element at index {@code i} to
+     * {@code newValue} if the element's current value {@code == expectedValue},
+     * with memory effects as specified by {@link VarHandle#weakCompareAndSetPlain}.
+     *
+     * @param i the index
+     * @param expectedValue the expected value
+     * @param newValue the new value
+     * @return {@code true} if successful
+     * @since 9
+     */
+    public final boolean weakCompareAndSetPlain(int i, long expectedValue, long newValue) {
+        return AA.weakCompareAndSetPlain(array, i, expectedValue, newValue);
+    }
+
+    /**
+     * Atomically increments the value of the element at index {@code i},
+     * with memory effects as specified by {@link VarHandle#getAndAdd}.
+     *
+     * <p>Equivalent to {@code getAndAdd(i, 1)}.
+     *
+     * @param i the index
+     * @return the previous value
+     */
+    public final long getAndIncrement(int i) {
+        return (long)AA.getAndAdd(array, i, 1L);
+    }
+
+    /**
+     * Atomically decrements the value of the element at index {@code i},
+     * with memory effects as specified by {@link VarHandle#getAndAdd}.
+     *
+     * <p>Equivalent to {@code getAndAdd(i, -1)}.
+     *
+     * @param i the index
+     * @return the previous value
+     */
+    public final long getAndDecrement(int i) {
+        return (long)AA.getAndAdd(array, i, -1L);
+    }
+
+    /**
+     * Atomically adds the given value to the element at index {@code i},
+     * with memory effects as specified by {@link VarHandle#getAndAdd}.
+     *
+     * @param i the index
+     * @param delta the value to add
+     * @return the previous value
+     */
+    public final long getAndAdd(int i, long delta) {
+        return (long)AA.getAndAdd(array, i, delta);
+    }
+
+    /**
+     * Atomically increments the value of the element at index {@code i},
+     * with memory effects as specified by {@link VarHandle#getAndAdd}.
+     *
+     * <p>Equivalent to {@code addAndGet(i, 1)}.
+     *
+     * @param i the index
+     * @return the updated value
+     */
+    public final long incrementAndGet(int i) {
+        return (long)AA.getAndAdd(array, i, 1L) + 1L;
+    }
+
+    /**
+     * Atomically decrements the value of the element at index {@code i},
+     * with memory effects as specified by {@link VarHandle#getAndAdd}.
+     *
+     * <p>Equivalent to {@code addAndGet(i, -1)}.
+     *
+     * @param i the index
+     * @return the updated value
+     */
+    public final long decrementAndGet(int i) {
+        return (long)AA.getAndAdd(array, i, -1L) - 1L;
+    }
+
+    /**
+     * Atomically adds the given value to the element at index {@code i},
+     * with memory effects as specified by {@link VarHandle#getAndAdd}.
+     *
+     * @param i the index
+     * @param delta the value to add
+     * @return the updated value
+     */
+    public long addAndGet(int i, long delta) {
+        return (long)AA.getAndAdd(array, i, delta) + delta;
+    }
+
+    /**
+     * Atomically updates (with memory effects as specified by {@link
+     * VarHandle#compareAndSet}) the element at index {@code i} with
+     * the results of applying the given function, returning the
+     * previous value. The function should be side-effect-free, since
+     * it may be re-applied when attempted updates fail due to
+     * contention among threads.
+     *
+     * @param i the index
+     * @param updateFunction a side-effect-free function
+     * @return the previous value
+     * @since 1.8
+     */
+    public final long getAndUpdate(int i, LongUnaryOperator updateFunction) {
+        long prev = get(i), next = 0L;
+        for (boolean haveNext = false;;) {
+            if (!haveNext)
+                next = updateFunction.applyAsLong(prev);
+            if (weakCompareAndSetVolatile(i, prev, next))
+                return prev;
+            haveNext = (prev == (prev = get(i)));
+        }
+    }
+
+    /**
+     * Atomically updates (with memory effects as specified by {@link
+     * VarHandle#compareAndSet}) the element at index {@code i} with
+     * the results of applying the given function, returning the
+     * updated value. The function should be side-effect-free, since it
+     * may be re-applied when attempted updates fail due to contention
+     * among threads.
+     *
+     * @param i the index
+     * @param updateFunction a side-effect-free function
+     * @return the updated value
+     * @since 1.8
+     */
+    public final long updateAndGet(int i, LongUnaryOperator updateFunction) {
+        long prev = get(i), next = 0L;
+        for (boolean haveNext = false;;) {
+            if (!haveNext)
+                next = updateFunction.applyAsLong(prev);
+            if (weakCompareAndSetVolatile(i, prev, next))
+                return next;
+            haveNext = (prev == (prev = get(i)));
+        }
+    }
+
+    /**
+     * Atomically updates (with memory effects as specified by {@link
+     * VarHandle#compareAndSet}) the element at index {@code i} with
+     * the results of applying the given function to the current and
+     * given values, returning the previous value. The function should
+     * be side-effect-free, since it may be re-applied when attempted
+     * updates fail due to contention among threads.  The function is
+     * applied with the current value of the element at index {@code i}
+     * as its first argument, and the given update as the second
+     * argument.
+     *
+     * @param i the index
+     * @param x the update value
+     * @param accumulatorFunction a side-effect-free function of two arguments
+     * @return the previous value
+     * @since 1.8
+     */
+    public final long getAndAccumulate(int i, long x,
+                                      LongBinaryOperator accumulatorFunction) {
+        long prev = get(i), next = 0L;
+        for (boolean haveNext = false;;) {
+            if (!haveNext)
+                next = accumulatorFunction.applyAsLong(prev, x);
+            if (weakCompareAndSetVolatile(i, prev, next))
+                return prev;
+            haveNext = (prev == (prev = get(i)));
+        }
+    }
+
+    /**
+     * Atomically updates (with memory effects as specified by {@link
+     * VarHandle#compareAndSet}) the element at index {@code i} with
+     * the results of applying the given function to the current and
+     * given values, returning the updated value. The function should
+     * be side-effect-free, since it may be re-applied when attempted
+     * updates fail due to contention among threads.  The function is
+     * applied with the current value of the element at index {@code i}
+     * as its first argument, and the given update as the second
+     * argument.
+     *
+     * @param i the index
+     * @param x the update value
+     * @param accumulatorFunction a side-effect-free function of two arguments
+     * @return the updated value
+     * @since 1.8
+     */
+    public final long accumulateAndGet(int i, long x,
+                                      LongBinaryOperator accumulatorFunction) {
+        long prev = get(i), next = 0L;
+        for (boolean haveNext = false;;) {
+            if (!haveNext)
+                next = accumulatorFunction.applyAsLong(prev, x);
+            if (weakCompareAndSetVolatile(i, prev, next))
+                return next;
+            haveNext = (prev == (prev = get(i)));
+        }
+    }
+
+    /**
+     * Returns the String representation of the current values of array.
+     * @return the String representation of the current values of array
+     */
+    public String toString() {
+        int iMax = array.length - 1;
+        if (iMax == -1)
+            return "[]";
+
+        StringBuilder b = new StringBuilder();
+        b.append('[');
+        for (int i = 0; ; i++) {
+            b.append(get(i));
+            if (i == iMax)
+                return b.append(']').toString();
+            b.append(',').append(' ');
+        }
+    }
+
+    // jdk9
+
+    /**
+     * Returns the current value of the element at index {@code i},
+     * with memory semantics of reading as if the variable was declared
+     * non-{@code volatile}.
+     *
+     * @param i the index
+     * @return the value
+     * @since 9
+     */
+    public final long getPlain(int i) {
+        return (long)AA.get(array, i);
+    }
+
+    /**
+     * Sets the element at index {@code i} to {@code newValue},
+     * with memory semantics of setting as if the variable was
+     * declared non-{@code volatile} and non-{@code final}.
+     *
+     * @param i the index
+     * @param newValue the new value
+     * @since 9
+     */
+    public final void setPlain(int i, long newValue) {
+        AA.set(array, i, newValue);
+    }
+
+    /**
+     * Returns the current value of the element at index {@code i},
+     * with memory effects as specified by {@link VarHandle#getOpaque}.
+     *
+     * @param i the index
+     * @return the value
+     * @since 9
+     */
+    public final long getOpaque(int i) {
+        return (long)AA.getOpaque(array, i);
+    }
+
+    /**
+     * Sets the element at index {@code i} to {@code newValue},
+     * with memory effects as specified by {@link VarHandle#setOpaque}.
+     *
+     * @param i the index
+     * @param newValue the new value
+     * @since 9
+     */
+    public final void setOpaque(int i, long newValue) {
+        AA.setOpaque(array, i, newValue);
+    }
+
+    /**
+     * Returns the current value of the element at index {@code i},
+     * with memory effects as specified by {@link VarHandle#getAcquire}.
+     *
+     * @param i the index
+     * @return the value
+     * @since 9
+     */
+    public final long getAcquire(int i) {
+        return (long)AA.getAcquire(array, i);
+    }
+
+    /**
+     * Sets the element at index {@code i} to {@code newValue},
+     * with memory effects as specified by {@link VarHandle#setRelease}.
+     *
+     * @param i the index
+     * @param newValue the new value
+     * @since 9
+     */
+    public final void setRelease(int i, long newValue) {
+        AA.setRelease(array, i, newValue);
+    }
+
+    /**
+     * Atomically sets the element at index {@code i} to {@code newValue}
+     * if the element's current value, referred to as the <em>witness
+     * value</em>, {@code == expectedValue},
+     * with memory effects as specified by
+     * {@link VarHandle#compareAndExchange}.
+     *
+     * @param i the index
+     * @param expectedValue the expected value
+     * @param newValue the new value
+     * @return the witness value, which will be the same as the
+     * expected value if successful
+     * @since 9
+     */
+    public final long compareAndExchange(int i, long expectedValue, long newValue) {
+        return (long)AA.compareAndExchange(array, i, expectedValue, newValue);
+    }
+
+    /**
+     * Atomically sets the element at index {@code i} to {@code newValue}
+     * if the element's current value, referred to as the <em>witness
+     * value</em>, {@code == expectedValue},
+     * with memory effects as specified by
+     * {@link VarHandle#compareAndExchangeAcquire}.
+     *
+     * @param i the index
+     * @param expectedValue the expected value
+     * @param newValue the new value
+     * @return the witness value, which will be the same as the
+     * expected value if successful
+     * @since 9
+     */
+    public final long compareAndExchangeAcquire(int i, long expectedValue, long newValue) {
+        return (long)AA.compareAndExchangeAcquire(array, i, expectedValue, newValue);
+    }
+
+    /**
+     * Atomically sets the element at index {@code i} to {@code newValue}
+     * if the element's current value, referred to as the <em>witness
+     * value</em>, {@code == expectedValue},
+     * with memory effects as specified by
+     * {@link VarHandle#compareAndExchangeRelease}.
+     *
+     * @param i the index
+     * @param expectedValue the expected value
+     * @param newValue the new value
+     * @return the witness value, which will be the same as the
+     * expected value if successful
+     * @since 9
+     */
+    public final long compareAndExchangeRelease(int i, long expectedValue, long newValue) {
+        return (long)AA.compareAndExchangeRelease(array, i, expectedValue, newValue);
+    }
+
+    /**
+     * Possibly atomically sets the element at index {@code i} to
+     * {@code newValue} if the element's current value {@code == expectedValue},
+     * with memory effects as specified by
+     * {@link VarHandle#weakCompareAndSet}.
+     *
+     * @param i the index
+     * @param expectedValue the expected value
+     * @param newValue the new value
+     * @return {@code true} if successful
+     * @since 9
+     */
+    public final boolean weakCompareAndSetVolatile(int i, long expectedValue, long newValue) {
+        return AA.weakCompareAndSet(array, i, expectedValue, newValue);
+    }
+
+    /**
+     * Possibly atomically sets the element at index {@code i} to
+     * {@code newValue} if the element's current value {@code == expectedValue},
+     * with memory effects as specified by
+     * {@link VarHandle#weakCompareAndSetAcquire}.
+     *
+     * @param i the index
+     * @param expectedValue the expected value
+     * @param newValue the new value
+     * @return {@code true} if successful
+     * @since 9
+     */
+    public final boolean weakCompareAndSetAcquire(int i, long expectedValue, long newValue) {
+        return AA.weakCompareAndSetAcquire(array, i, expectedValue, newValue);
+    }
+
+    /**
+     * Possibly atomically sets the element at index {@code i} to
+     * {@code newValue} if the element's current value {@code == expectedValue},
+     * with memory effects as specified by
+     * {@link VarHandle#weakCompareAndSetRelease}.
+     *
+     * @param i the index
+     * @param expectedValue the expected value
+     * @param newValue the new value
+     * @return {@code true} if successful
+     * @since 9
+     */
+    public final boolean weakCompareAndSetRelease(int i, long expectedValue, long newValue) {
+        return AA.weakCompareAndSetRelease(array, i, expectedValue, newValue);
+    }
+
+}

src/java.base/share/classes/java/util/concurrent/atomic/AtomicLongFieldUpdater.java

@@ -0,0 +1,661 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent.atomic;
+
+import java.lang.reflect.Field;
+import java.lang.reflect.Modifier;
+import java.security.AccessController;
+import java.security.PrivilegedActionException;
+import java.security.PrivilegedExceptionAction;
+import java.util.Objects;
+import java.util.function.LongBinaryOperator;
+import java.util.function.LongUnaryOperator;
+import jdk.internal.misc.Unsafe;
+import jdk.internal.reflect.CallerSensitive;
+import jdk.internal.reflect.Reflection;
+import java.lang.invoke.VarHandle;
+
+/**
+ * A reflection-based utility that enables atomic updates to
+ * designated {@code volatile long} fields of designated classes.
+ * This class is designed for use in atomic data structures in which
+ * several fields of the same node are independently subject to atomic
+ * updates.
+ *
+ * <p>Note that the guarantees of the {@code compareAndSet}
+ * method in this class are weaker than in other atomic classes.
+ * Because this class cannot ensure that all uses of the field
+ * are appropriate for purposes of atomic access, it can
+ * guarantee atomicity only with respect to other invocations of
+ * {@code compareAndSet} and {@code set} on the same updater.
+ *
+ * <p>Object arguments for parameters of type {@code T} that are not
+ * instances of the class passed to {@link #newUpdater} will result in
+ * a {@link ClassCastException} being thrown.
+ *
+ * @since 1.5
+ * @author Doug Lea
+ * @param <T> The type of the object holding the updatable field
+ */
+public abstract class AtomicLongFieldUpdater<T> {
+    /**
+     * Creates and returns an updater for objects with the given field.
+     * The Class argument is needed to check that reflective types and
+     * generic types match.
+     *
+     * @param tclass the class of the objects holding the field
+     * @param fieldName the name of the field to be updated
+     * @param <U> the type of instances of tclass
+     * @return the updater
+     * @throws IllegalArgumentException if the field is not a
+     * volatile long type
+     * @throws RuntimeException with a nested reflection-based
+     * exception if the class does not hold field or is the wrong type,
+     * or the field is inaccessible to the caller according to Java language
+     * access control
+     */
+    @CallerSensitive
+    public static <U> AtomicLongFieldUpdater<U> newUpdater(Class<U> tclass,
+                                                           String fieldName) {
+        Class<?> caller = Reflection.getCallerClass();
+        if (AtomicLong.VM_SUPPORTS_LONG_CAS)
+            return new CASUpdater<U>(tclass, fieldName, caller);
+        else
+            return new LockedUpdater<U>(tclass, fieldName, caller);
+    }
+
+    /**
+     * Protected do-nothing constructor for use by subclasses.
+     */
+    protected AtomicLongFieldUpdater() {
+    }
+
+    /**
+     * Atomically sets the field of the given object managed by this updater
+     * to the given updated value if the current value {@code ==} the
+     * expected value. This method is guaranteed to be atomic with respect to
+     * other calls to {@code compareAndSet} and {@code set}, but not
+     * necessarily with respect to other changes in the field.
+     *
+     * @param obj An object whose field to conditionally set
+     * @param expect the expected value
+     * @param update the new value
+     * @return {@code true} if successful
+     */
+    public abstract boolean compareAndSet(T obj, long expect, long update);
+
+    /**
+     * Atomically sets the field of the given object managed by this updater
+     * to the given updated value if the current value {@code ==} the
+     * expected value. This method is guaranteed to be atomic with respect to
+     * other calls to {@code compareAndSet} and {@code set}, but not
+     * necessarily with respect to other changes in the field.
+     *
+     * <p><a href="package-summary.html#weakCompareAndSet">May fail
+     * spuriously and does not provide ordering guarantees</a>, so is
+     * only rarely an appropriate alternative to {@code compareAndSet}.
+     *
+     * @param obj An object whose field to conditionally set
+     * @param expect the expected value
+     * @param update the new value
+     * @return {@code true} if successful
+     */
+    public abstract boolean weakCompareAndSet(T obj, long expect, long update);
+
+    /**
+     * Sets the field of the given object managed by this updater to the
+     * given updated value. This operation is guaranteed to act as a volatile
+     * store with respect to subsequent invocations of {@code compareAndSet}.
+     *
+     * @param obj An object whose field to set
+     * @param newValue the new value
+     */
+    public abstract void set(T obj, long newValue);
+
+    /**
+     * Eventually sets the field of the given object managed by this
+     * updater to the given updated value.
+     *
+     * @param obj An object whose field to set
+     * @param newValue the new value
+     * @since 1.6
+     */
+    public abstract void lazySet(T obj, long newValue);
+
+    /**
+     * Returns the current value held in the field of the given object
+     * managed by this updater.
+     *
+     * @param obj An object whose field to get
+     * @return the current value
+     */
+    public abstract long get(T obj);
+
+    /**
+     * Atomically sets the field of the given object managed by this updater
+     * to the given value and returns the old value.
+     *
+     * @param obj An object whose field to get and set
+     * @param newValue the new value
+     * @return the previous value
+     */
+    public long getAndSet(T obj, long newValue) {
+        long prev;
+        do {
+            prev = get(obj);
+        } while (!compareAndSet(obj, prev, newValue));
+        return prev;
+    }
+
+    /**
+     * Atomically increments by one the current value of the field of the
+     * given object managed by this updater.
+     *
+     * @param obj An object whose field to get and set
+     * @return the previous value
+     */
+    public long getAndIncrement(T obj) {
+        long prev, next;
+        do {
+            prev = get(obj);
+            next = prev + 1;
+        } while (!compareAndSet(obj, prev, next));
+        return prev;
+    }
+
+    /**
+     * Atomically decrements by one the current value of the field of the
+     * given object managed by this updater.
+     *
+     * @param obj An object whose field to get and set
+     * @return the previous value
+     */
+    public long getAndDecrement(T obj) {
+        long prev, next;
+        do {
+            prev = get(obj);
+            next = prev - 1;
+        } while (!compareAndSet(obj, prev, next));
+        return prev;
+    }
+
+    /**
+     * Atomically adds the given value to the current value of the field of
+     * the given object managed by this updater.
+     *
+     * @param obj An object whose field to get and set
+     * @param delta the value to add
+     * @return the previous value
+     */
+    public long getAndAdd(T obj, long delta) {
+        long prev, next;
+        do {
+            prev = get(obj);
+            next = prev + delta;
+        } while (!compareAndSet(obj, prev, next));
+        return prev;
+    }
+
+    /**
+     * Atomically increments by one the current value of the field of the
+     * given object managed by this updater.
+     *
+     * @param obj An object whose field to get and set
+     * @return the updated value
+     */
+    public long incrementAndGet(T obj) {
+        long prev, next;
+        do {
+            prev = get(obj);
+            next = prev + 1;
+        } while (!compareAndSet(obj, prev, next));
+        return next;
+    }
+
+    /**
+     * Atomically decrements by one the current value of the field of the
+     * given object managed by this updater.
+     *
+     * @param obj An object whose field to get and set
+     * @return the updated value
+     */
+    public long decrementAndGet(T obj) {
+        long prev, next;
+        do {
+            prev = get(obj);
+            next = prev - 1;
+        } while (!compareAndSet(obj, prev, next));
+        return next;
+    }
+
+    /**
+     * Atomically adds the given value to the current value of the field of
+     * the given object managed by this updater.
+     *
+     * @param obj An object whose field to get and set
+     * @param delta the value to add
+     * @return the updated value
+     */
+    public long addAndGet(T obj, long delta) {
+        long prev, next;
+        do {
+            prev = get(obj);
+            next = prev + delta;
+        } while (!compareAndSet(obj, prev, next));
+        return next;
+    }
+
+    /**
+     * Atomically updates (with memory effects as specified by {@link
+     * VarHandle#compareAndSet}) the field of the given object managed
+     * by this updater with the results of applying the given
+     * function, returning the previous value. The function should be
+     * side-effect-free, since it may be re-applied when attempted
+     * updates fail due to contention among threads.
+     *
+     * @param obj An object whose field to get and set
+     * @param updateFunction a side-effect-free function
+     * @return the previous value
+     * @since 1.8
+     */
+    public final long getAndUpdate(T obj, LongUnaryOperator updateFunction) {
+        long prev, next;
+        do {
+            prev = get(obj);
+            next = updateFunction.applyAsLong(prev);
+        } while (!compareAndSet(obj, prev, next));
+        return prev;
+    }
+
+    /**
+     * Atomically updates (with memory effects as specified by {@link
+     * VarHandle#compareAndSet}) the field of the given object managed
+     * by this updater with the results of applying the given
+     * function, returning the updated value. The function should be
+     * side-effect-free, since it may be re-applied when attempted
+     * updates fail due to contention among threads.
+     *
+     * @param obj An object whose field to get and set
+     * @param updateFunction a side-effect-free function
+     * @return the updated value
+     * @since 1.8
+     */
+    public final long updateAndGet(T obj, LongUnaryOperator updateFunction) {
+        long prev, next;
+        do {
+            prev = get(obj);
+            next = updateFunction.applyAsLong(prev);
+        } while (!compareAndSet(obj, prev, next));
+        return next;
+    }
+
+    /**
+     * Atomically updates (with memory effects as specified by {@link
+     * VarHandle#compareAndSet}) the field of the given object managed
+     * by this updater with the results of applying the given function
+     * to the current and given values, returning the previous value.
+     * The function should be side-effect-free, since it may be
+     * re-applied when attempted updates fail due to contention among
+     * threads.  The function is applied with the current value as its
+     * first argument, and the given update as the second argument.
+     *
+     * @param obj An object whose field to get and set
+     * @param x the update value
+     * @param accumulatorFunction a side-effect-free function of two arguments
+     * @return the previous value
+     * @since 1.8
+     */
+    public final long getAndAccumulate(T obj, long x,
+                                       LongBinaryOperator accumulatorFunction) {
+        long prev, next;
+        do {
+            prev = get(obj);
+            next = accumulatorFunction.applyAsLong(prev, x);
+        } while (!compareAndSet(obj, prev, next));
+        return prev;
+    }
+
+    /**
+     * Atomically updates (with memory effects as specified by {@link
+     * VarHandle#compareAndSet}) the field of the given object managed
+     * by this updater with the results of applying the given function
+     * to the current and given values, returning the updated value.
+     * The function should be side-effect-free, since it may be
+     * re-applied when attempted updates fail due to contention among
+     * threads.  The function is applied with the current value as its
+     * first argument, and the given update as the second argument.
+     *
+     * @param obj An object whose field to get and set
+     * @param x the update value
+     * @param accumulatorFunction a side-effect-free function of two arguments
+     * @return the updated value
+     * @since 1.8
+     */
+    public final long accumulateAndGet(T obj, long x,
+                                       LongBinaryOperator accumulatorFunction) {
+        long prev, next;
+        do {
+            prev = get(obj);
+            next = accumulatorFunction.applyAsLong(prev, x);
+        } while (!compareAndSet(obj, prev, next));
+        return next;
+    }
+
+    private static final class CASUpdater<T> extends AtomicLongFieldUpdater<T> {
+        private static final Unsafe U = Unsafe.getUnsafe();
+        private final long offset;
+        /**
+         * if field is protected, the subclass constructing updater, else
+         * the same as tclass
+         */
+        private final Class<?> cclass;
+        /** class holding the field */
+        private final Class<T> tclass;
+
+        CASUpdater(final Class<T> tclass, final String fieldName,
+                   final Class<?> caller) {
+            final Field field;
+            final int modifiers;
+            try {
+                field = AccessController.doPrivileged(
+                    new PrivilegedExceptionAction<Field>() {
+                        public Field run() throws NoSuchFieldException {
+                            return tclass.getDeclaredField(fieldName);
+                        }
+                    });
+                modifiers = field.getModifiers();
+                sun.reflect.misc.ReflectUtil.ensureMemberAccess(
+                    caller, tclass, null, modifiers);
+                ClassLoader cl = tclass.getClassLoader();
+                ClassLoader ccl = caller.getClassLoader();
+                if ((ccl != null) && (ccl != cl) &&
+                    ((cl == null) || !isAncestor(cl, ccl))) {
+                    sun.reflect.misc.ReflectUtil.checkPackageAccess(tclass);
+                }
+            } catch (PrivilegedActionException pae) {
+                throw new RuntimeException(pae.getException());
+            } catch (Exception ex) {
+                throw new RuntimeException(ex);
+            }
+
+            if (field.getType() != long.class)
+                throw new IllegalArgumentException("Must be long type");
+
+            if (!Modifier.isVolatile(modifiers))
+                throw new IllegalArgumentException("Must be volatile type");
+
+            // Access to protected field members is restricted to receivers only
+            // of the accessing class, or one of its subclasses, and the
+            // accessing class must in turn be a subclass (or package sibling)
+            // of the protected member's defining class.
+            // If the updater refers to a protected field of a declaring class
+            // outside the current package, the receiver argument will be
+            // narrowed to the type of the accessing class.
+            this.cclass = (Modifier.isProtected(modifiers) &&
+                           tclass.isAssignableFrom(caller) &&
+                           !isSamePackage(tclass, caller))
+                          ? caller : tclass;
+            this.tclass = tclass;
+            this.offset = U.objectFieldOffset(field);
+        }
+
+        /**
+         * Checks that target argument is instance of cclass.  On
+         * failure, throws cause.
+         */
+        private final void accessCheck(T obj) {
+            if (!cclass.isInstance(obj))
+                throwAccessCheckException(obj);
+        }
+
+        /**
+         * Throws access exception if accessCheck failed due to
+         * protected access, else ClassCastException.
+         */
+        private final void throwAccessCheckException(T obj) {
+            if (cclass == tclass)
+                throw new ClassCastException();
+            else
+                throw new RuntimeException(
+                    new IllegalAccessException(
+                        "Class " +
+                        cclass.getName() +
+                        " can not access a protected member of class " +
+                        tclass.getName() +
+                        " using an instance of " +
+                        obj.getClass().getName()));
+        }
+
+        public final boolean compareAndSet(T obj, long expect, long update) {
+            accessCheck(obj);
+            return U.compareAndSetLong(obj, offset, expect, update);
+        }
+
+        public final boolean weakCompareAndSet(T obj, long expect, long update) {
+            accessCheck(obj);
+            return U.compareAndSetLong(obj, offset, expect, update);
+        }
+
+        public final void set(T obj, long newValue) {
+            accessCheck(obj);
+            U.putLongVolatile(obj, offset, newValue);
+        }
+
+        public final void lazySet(T obj, long newValue) {
+            accessCheck(obj);
+            U.putLongRelease(obj, offset, newValue);
+        }
+
+        public final long get(T obj) {
+            accessCheck(obj);
+            return U.getLongVolatile(obj, offset);
+        }
+
+        public final long getAndSet(T obj, long newValue) {
+            accessCheck(obj);
+            return U.getAndSetLong(obj, offset, newValue);
+        }
+
+        public final long getAndAdd(T obj, long delta) {
+            accessCheck(obj);
+            return U.getAndAddLong(obj, offset, delta);
+        }
+
+        public final long getAndIncrement(T obj) {
+            return getAndAdd(obj, 1);
+        }
+
+        public final long getAndDecrement(T obj) {
+            return getAndAdd(obj, -1);
+        }
+
+        public final long incrementAndGet(T obj) {
+            return getAndAdd(obj, 1) + 1;
+        }
+
+        public final long decrementAndGet(T obj) {
+            return getAndAdd(obj, -1) - 1;
+        }
+
+        public final long addAndGet(T obj, long delta) {
+            return getAndAdd(obj, delta) + delta;
+        }
+    }
+
+    private static final class LockedUpdater<T> extends AtomicLongFieldUpdater<T> {
+        private static final Unsafe U = Unsafe.getUnsafe();
+        private final long offset;
+        /**
+         * if field is protected, the subclass constructing updater, else
+         * the same as tclass
+         */
+        private final Class<?> cclass;
+        /** class holding the field */
+        private final Class<T> tclass;
+
+        LockedUpdater(final Class<T> tclass, final String fieldName,
+                      final Class<?> caller) {
+            final Field field;
+            final int modifiers;
+            try {
+                field = AccessController.doPrivileged(
+                    new PrivilegedExceptionAction<Field>() {
+                        public Field run() throws NoSuchFieldException {
+                            return tclass.getDeclaredField(fieldName);
+                        }
+                    });
+                modifiers = field.getModifiers();
+                sun.reflect.misc.ReflectUtil.ensureMemberAccess(
+                    caller, tclass, null, modifiers);
+                ClassLoader cl = tclass.getClassLoader();
+                ClassLoader ccl = caller.getClassLoader();
+                if ((ccl != null) && (ccl != cl) &&
+                    ((cl == null) || !isAncestor(cl, ccl))) {
+                    sun.reflect.misc.ReflectUtil.checkPackageAccess(tclass);
+                }
+            } catch (PrivilegedActionException pae) {
+                throw new RuntimeException(pae.getException());
+            } catch (Exception ex) {
+                throw new RuntimeException(ex);
+            }
+
+            if (field.getType() != long.class)
+                throw new IllegalArgumentException("Must be long type");
+
+            if (!Modifier.isVolatile(modifiers))
+                throw new IllegalArgumentException("Must be volatile type");
+
+            // Access to protected field members is restricted to receivers only
+            // of the accessing class, or one of its subclasses, and the
+            // accessing class must in turn be a subclass (or package sibling)
+            // of the protected member's defining class.
+            // If the updater refers to a protected field of a declaring class
+            // outside the current package, the receiver argument will be
+            // narrowed to the type of the accessing class.
+            this.cclass = (Modifier.isProtected(modifiers) &&
+                           tclass.isAssignableFrom(caller) &&
+                           !isSamePackage(tclass, caller))
+                          ? caller : tclass;
+            this.tclass = tclass;
+            this.offset = U.objectFieldOffset(field);
+        }
+
+        /**
+         * Checks that target argument is instance of cclass.  On
+         * failure, throws cause.
+         */
+        private final void accessCheck(T obj) {
+            if (!cclass.isInstance(obj))
+                throw accessCheckException(obj);
+        }
+
+        /**
+         * Returns access exception if accessCheck failed due to
+         * protected access, else ClassCastException.
+         */
+        private final RuntimeException accessCheckException(T obj) {
+            if (cclass == tclass)
+                return new ClassCastException();
+            else
+                return new RuntimeException(
+                    new IllegalAccessException(
+                        "Class " +
+                        cclass.getName() +
+                        " can not access a protected member of class " +
+                        tclass.getName() +
+                        " using an instance of " +
+                        obj.getClass().getName()));
+        }
+
+        public final boolean compareAndSet(T obj, long expect, long update) {
+            accessCheck(obj);
+            synchronized (this) {
+                long v = U.getLong(obj, offset);
+                if (v != expect)
+                    return false;
+                U.putLong(obj, offset, update);
+                return true;
+            }
+        }
+
+        public final boolean weakCompareAndSet(T obj, long expect, long update) {
+            return compareAndSet(obj, expect, update);
+        }
+
+        public final void set(T obj, long newValue) {
+            accessCheck(obj);
+            synchronized (this) {
+                U.putLong(obj, offset, newValue);
+            }
+        }
+
+        public final void lazySet(T obj, long newValue) {
+            set(obj, newValue);
+        }
+
+        public final long get(T obj) {
+            accessCheck(obj);
+            synchronized (this) {
+                return U.getLong(obj, offset);
+            }
+        }
+    }
+
+    /**
+     * Returns true if the second classloader can be found in the first
+     * classloader's delegation chain.
+     * Equivalent to the inaccessible: first.isAncestor(second).
+     */
+    static boolean isAncestor(ClassLoader first, ClassLoader second) {
+        ClassLoader acl = first;
+        do {
+            acl = acl.getParent();
+            if (second == acl) {
+                return true;
+            }
+        } while (acl != null);
+        return false;
+    }
+
+    /**
+     * Returns true if the two classes have the same class loader and
+     * package qualifier
+     */
+    static boolean isSamePackage(Class<?> class1, Class<?> class2) {
+        return class1.getClassLoader() == class2.getClassLoader()
+               && Objects.equals(class1.getPackageName(), class2.getPackageName());
+    }
+}

src/java.base/share/classes/java/util/concurrent/atomic/AtomicMarkableReference.java

@@ -0,0 +1,209 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent.atomic;
+
+import java.lang.invoke.MethodHandles;
+import java.lang.invoke.VarHandle;
+
+/**
+ * An {@code AtomicMarkableReference} maintains an object reference
+ * along with a mark bit, that can be updated atomically.
+ *
+ * <p>Implementation note: This implementation maintains markable
+ * references by creating internal objects representing "boxed"
+ * [reference, boolean] pairs.
+ *
+ * @since 1.5
+ * @author Doug Lea
+ * @param <V> The type of object referred to by this reference
+ */
+public class AtomicMarkableReference<V> {
+
+    private static class Pair<T> {
+        final T reference;
+        final boolean mark;
+        private Pair(T reference, boolean mark) {
+            this.reference = reference;
+            this.mark = mark;
+        }
+        static <T> Pair<T> of(T reference, boolean mark) {
+            return new Pair<T>(reference, mark);
+        }
+    }
+
+    private volatile Pair<V> pair;
+
+    /**
+     * Creates a new {@code AtomicMarkableReference} with the given
+     * initial values.
+     *
+     * @param initialRef the initial reference
+     * @param initialMark the initial mark
+     */
+    public AtomicMarkableReference(V initialRef, boolean initialMark) {
+        pair = Pair.of(initialRef, initialMark);
+    }
+
+    /**
+     * Returns the current value of the reference.
+     *
+     * @return the current value of the reference
+     */
+    public V getReference() {
+        return pair.reference;
+    }
+
+    /**
+     * Returns the current value of the mark.
+     *
+     * @return the current value of the mark
+     */
+    public boolean isMarked() {
+        return pair.mark;
+    }
+
+    /**
+     * Returns the current values of both the reference and the mark.
+     * Typical usage is {@code boolean[1] holder; ref = v.get(holder); }.
+     *
+     * @param markHolder an array of size of at least one. On return,
+     * {@code markHolder[0]} will hold the value of the mark.
+     * @return the current value of the reference
+     */
+    public V get(boolean[] markHolder) {
+        Pair<V> pair = this.pair;
+        markHolder[0] = pair.mark;
+        return pair.reference;
+    }
+
+    /**
+     * Atomically sets the value of both the reference and mark
+     * to the given update values if the
+     * current reference is {@code ==} to the expected reference
+     * and the current mark is equal to the expected mark.
+     *
+     * <p><a href="package-summary.html#weakCompareAndSet">May fail
+     * spuriously and does not provide ordering guarantees</a>, so is
+     * only rarely an appropriate alternative to {@code compareAndSet}.
+     *
+     * @param expectedReference the expected value of the reference
+     * @param newReference the new value for the reference
+     * @param expectedMark the expected value of the mark
+     * @param newMark the new value for the mark
+     * @return {@code true} if successful
+     */
+    public boolean weakCompareAndSet(V       expectedReference,
+                                     V       newReference,
+                                     boolean expectedMark,
+                                     boolean newMark) {
+        return compareAndSet(expectedReference, newReference,
+                             expectedMark, newMark);
+    }
+
+    /**
+     * Atomically sets the value of both the reference and mark
+     * to the given update values if the
+     * current reference is {@code ==} to the expected reference
+     * and the current mark is equal to the expected mark.
+     *
+     * @param expectedReference the expected value of the reference
+     * @param newReference the new value for the reference
+     * @param expectedMark the expected value of the mark
+     * @param newMark the new value for the mark
+     * @return {@code true} if successful
+     */
+    public boolean compareAndSet(V       expectedReference,
+                                 V       newReference,
+                                 boolean expectedMark,
+                                 boolean newMark) {
+        Pair<V> current = pair;
+        return
+            expectedReference == current.reference &&
+            expectedMark == current.mark &&
+            ((newReference == current.reference &&
+              newMark == current.mark) ||
+             casPair(current, Pair.of(newReference, newMark)));
+    }
+
+    /**
+     * Unconditionally sets the value of both the reference and mark.
+     *
+     * @param newReference the new value for the reference
+     * @param newMark the new value for the mark
+     */
+    public void set(V newReference, boolean newMark) {
+        Pair<V> current = pair;
+        if (newReference != current.reference || newMark != current.mark)
+            this.pair = Pair.of(newReference, newMark);
+    }
+
+    /**
+     * Atomically sets the value of the mark to the given update value
+     * if the current reference is {@code ==} to the expected
+     * reference.  Any given invocation of this operation may fail
+     * (return {@code false}) spuriously, but repeated invocation
+     * when the current value holds the expected value and no other
+     * thread is also attempting to set the value will eventually
+     * succeed.
+     *
+     * @param expectedReference the expected value of the reference
+     * @param newMark the new value for the mark
+     * @return {@code true} if successful
+     */
+    public boolean attemptMark(V expectedReference, boolean newMark) {
+        Pair<V> current = pair;
+        return
+            expectedReference == current.reference &&
+            (newMark == current.mark ||
+             casPair(current, Pair.of(expectedReference, newMark)));
+    }
+
+    // VarHandle mechanics
+    private static final VarHandle PAIR;
+    static {
+        try {
+            MethodHandles.Lookup l = MethodHandles.lookup();
+            PAIR = l.findVarHandle(AtomicMarkableReference.class, "pair",
+                                   Pair.class);
+        } catch (ReflectiveOperationException e) {
+            throw new Error(e);
+        }
+    }
+
+    private boolean casPair(Pair<V> cmp, Pair<V> val) {
+        return PAIR.compareAndSet(this, cmp, val);
+    }
+}

src/java.base/share/classes/java/util/concurrent/atomic/AtomicReference.java

@@ -0,0 +1,440 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent.atomic;
+
+import java.lang.invoke.MethodHandles;
+import java.lang.invoke.VarHandle;
+import java.util.function.BinaryOperator;
+import java.util.function.UnaryOperator;
+
+/**
+ * An object reference that may be updated atomically.  See the {@link
+ * VarHandle} specification for descriptions of the properties of
+ * atomic accesses.
+ * @since 1.5
+ * @author Doug Lea
+ * @param <V> The type of object referred to by this reference
+ */
+public class AtomicReference<V> implements java.io.Serializable {
+    private static final long serialVersionUID = -1848883965231344442L;
+    private static final VarHandle VALUE;
+    static {
+        try {
+            MethodHandles.Lookup l = MethodHandles.lookup();
+            VALUE = l.findVarHandle(AtomicReference.class, "value", Object.class);
+        } catch (ReflectiveOperationException e) {
+            throw new Error(e);
+        }
+    }
+
+    private volatile V value;
+
+    /**
+     * Creates a new AtomicReference with the given initial value.
+     *
+     * @param initialValue the initial value
+     */
+    public AtomicReference(V initialValue) {
+        value = initialValue;
+    }
+
+    /**
+     * Creates a new AtomicReference with null initial value.
+     */
+    public AtomicReference() {
+    }
+
+    /**
+     * Returns the current value,
+     * with memory effects as specified by {@link VarHandle#getVolatile}.
+     *
+     * @return the current value
+     */
+    public final V get() {
+        return value;
+    }
+
+    /**
+     * Sets the value to {@code newValue},
+     * with memory effects as specified by {@link VarHandle#setVolatile}.
+     *
+     * @param newValue the new value
+     */
+    public final void set(V newValue) {
+        value = newValue;
+    }
+
+    /**
+     * Sets the value to {@code newValue},
+     * with memory effects as specified by {@link VarHandle#setRelease}.
+     *
+     * @param newValue the new value
+     * @since 1.6
+     */
+    public final void lazySet(V newValue) {
+        VALUE.setRelease(this, newValue);
+    }
+
+    /**
+     * Atomically sets the value to {@code newValue}
+     * if the current value {@code == expectedValue},
+     * with memory effects as specified by {@link VarHandle#compareAndSet}.
+     *
+     * @param expectedValue the expected value
+     * @param newValue the new value
+     * @return {@code true} if successful. False return indicates that
+     * the actual value was not equal to the expected value.
+     */
+    public final boolean compareAndSet(V expectedValue, V newValue) {
+        return VALUE.compareAndSet(this, expectedValue, newValue);
+    }
+
+    /**
+     * Possibly atomically sets the value to {@code newValue}
+     * if the current value {@code == expectedValue},
+     * with memory effects as specified by {@link VarHandle#weakCompareAndSetPlain}.
+     *
+     * @deprecated This method has plain memory effects but the method
+     * name implies volatile memory effects (see methods such as
+     * {@link #compareAndExchange} and {@link #compareAndSet}).  To avoid
+     * confusion over plain or volatile memory effects it is recommended that
+     * the method {@link #weakCompareAndSetPlain} be used instead.
+     *
+     * @param expectedValue the expected value
+     * @param newValue the new value
+     * @return {@code true} if successful
+     * @see #weakCompareAndSetPlain
+     */
+    @Deprecated(since="9")
+    public final boolean weakCompareAndSet(V expectedValue, V newValue) {
+        return VALUE.weakCompareAndSetPlain(this, expectedValue, newValue);
+    }
+
+    /**
+     * Possibly atomically sets the value to {@code newValue}
+     * if the current value {@code == expectedValue},
+     * with memory effects as specified by {@link VarHandle#weakCompareAndSetPlain}.
+     *
+     * @param expectedValue the expected value
+     * @param newValue the new value
+     * @return {@code true} if successful
+     * @since 9
+     */
+    public final boolean weakCompareAndSetPlain(V expectedValue, V newValue) {
+        return VALUE.weakCompareAndSetPlain(this, expectedValue, newValue);
+    }
+
+    /**
+     * Atomically sets the value to {@code newValue} and returns the old value,
+     * with memory effects as specified by {@link VarHandle#getAndSet}.
+     *
+     * @param newValue the new value
+     * @return the previous value
+     */
+    @SuppressWarnings("unchecked")
+    public final V getAndSet(V newValue) {
+        return (V)VALUE.getAndSet(this, newValue);
+    }
+
+    /**
+     * Atomically updates (with memory effects as specified by {@link
+     * VarHandle#compareAndSet}) the current value with the results of
+     * applying the given function, returning the previous value. The
+     * function should be side-effect-free, since it may be re-applied
+     * when attempted updates fail due to contention among threads.
+     *
+     * @param updateFunction a side-effect-free function
+     * @return the previous value
+     * @since 1.8
+     */
+    public final V getAndUpdate(UnaryOperator<V> updateFunction) {
+        V prev = get(), next = null;
+        for (boolean haveNext = false;;) {
+            if (!haveNext)
+                next = updateFunction.apply(prev);
+            if (weakCompareAndSetVolatile(prev, next))
+                return prev;
+            haveNext = (prev == (prev = get()));
+        }
+    }
+
+    /**
+     * Atomically updates (with memory effects as specified by {@link
+     * VarHandle#compareAndSet}) the current value with the results of
+     * applying the given function, returning the updated value. The
+     * function should be side-effect-free, since it may be re-applied
+     * when attempted updates fail due to contention among threads.
+     *
+     * @param updateFunction a side-effect-free function
+     * @return the updated value
+     * @since 1.8
+     */
+    public final V updateAndGet(UnaryOperator<V> updateFunction) {
+        V prev = get(), next = null;
+        for (boolean haveNext = false;;) {
+            if (!haveNext)
+                next = updateFunction.apply(prev);
+            if (weakCompareAndSetVolatile(prev, next))
+                return next;
+            haveNext = (prev == (prev = get()));
+        }
+    }
+
+    /**
+     * Atomically updates (with memory effects as specified by {@link
+     * VarHandle#compareAndSet}) the current value with the results of
+     * applying the given function to the current and given values,
+     * returning the previous value. The function should be
+     * side-effect-free, since it may be re-applied when attempted
+     * updates fail due to contention among threads.  The function is
+     * applied with the current value as its first argument, and the
+     * given update as the second argument.
+     *
+     * @param x the update value
+     * @param accumulatorFunction a side-effect-free function of two arguments
+     * @return the previous value
+     * @since 1.8
+     */
+    public final V getAndAccumulate(V x,
+                                    BinaryOperator<V> accumulatorFunction) {
+        V prev = get(), next = null;
+        for (boolean haveNext = false;;) {
+            if (!haveNext)
+                next = accumulatorFunction.apply(prev, x);
+            if (weakCompareAndSetVolatile(prev, next))
+                return prev;
+            haveNext = (prev == (prev = get()));
+        }
+    }
+
+    /**
+     * Atomically updates (with memory effects as specified by {@link
+     * VarHandle#compareAndSet}) the current value with the results of
+     * applying the given function to the current and given values,
+     * returning the updated value. The function should be
+     * side-effect-free, since it may be re-applied when attempted
+     * updates fail due to contention among threads.  The function is
+     * applied with the current value as its first argument, and the
+     * given update as the second argument.
+     *
+     * @param x the update value
+     * @param accumulatorFunction a side-effect-free function of two arguments
+     * @return the updated value
+     * @since 1.8
+     */
+    public final V accumulateAndGet(V x,
+                                    BinaryOperator<V> accumulatorFunction) {
+        V prev = get(), next = null;
+        for (boolean haveNext = false;;) {
+            if (!haveNext)
+                next = accumulatorFunction.apply(prev, x);
+            if (weakCompareAndSetVolatile(prev, next))
+                return next;
+            haveNext = (prev == (prev = get()));
+        }
+    }
+
+    /**
+     * Returns the String representation of the current value.
+     * @return the String representation of the current value
+     */
+    public String toString() {
+        return String.valueOf(get());
+    }
+
+    // jdk9
+
+    /**
+     * Returns the current value, with memory semantics of reading as
+     * if the variable was declared non-{@code volatile}.
+     *
+     * @return the value
+     * @since 9
+     */
+    public final V getPlain() {
+        return (V)VALUE.get(this);
+    }
+
+    /**
+     * Sets the value to {@code newValue}, with memory semantics
+     * of setting as if the variable was declared non-{@code volatile}
+     * and non-{@code final}.
+     *
+     * @param newValue the new value
+     * @since 9
+     */
+    public final void setPlain(V newValue) {
+        VALUE.set(this, newValue);
+    }
+
+    /**
+     * Returns the current value,
+     * with memory effects as specified by {@link VarHandle#getOpaque}.
+     *
+     * @return the value
+     * @since 9
+     */
+    public final V getOpaque() {
+        return (V)VALUE.getOpaque(this);
+    }
+
+    /**
+     * Sets the value to {@code newValue},
+     * with memory effects as specified by {@link VarHandle#setOpaque}.
+     *
+     * @param newValue the new value
+     * @since 9
+     */
+    public final void setOpaque(V newValue) {
+        VALUE.setOpaque(this, newValue);
+    }
+
+    /**
+     * Returns the current value,
+     * with memory effects as specified by {@link VarHandle#getAcquire}.
+     *
+     * @return the value
+     * @since 9
+     */
+    public final V getAcquire() {
+        return (V)VALUE.getAcquire(this);
+    }
+
+    /**
+     * Sets the value to {@code newValue},
+     * with memory effects as specified by {@link VarHandle#setRelease}.
+     *
+     * @param newValue the new value
+     * @since 9
+     */
+    public final void setRelease(V newValue) {
+        VALUE.setRelease(this, newValue);
+    }
+
+    /**
+     * Atomically sets the value to {@code newValue} if the current value,
+     * referred to as the <em>witness value</em>, {@code == expectedValue},
+     * with memory effects as specified by
+     * {@link VarHandle#compareAndExchange}.
+     *
+     * @param expectedValue the expected value
+     * @param newValue the new value
+     * @return the witness value, which will be the same as the
+     * expected value if successful
+     * @since 9
+     */
+    public final V compareAndExchange(V expectedValue, V newValue) {
+        return (V)VALUE.compareAndExchange(this, expectedValue, newValue);
+    }
+
+    /**
+     * Atomically sets the value to {@code newValue} if the current value,
+     * referred to as the <em>witness value</em>, {@code == expectedValue},
+     * with memory effects as specified by
+     * {@link VarHandle#compareAndExchangeAcquire}.
+     *
+     * @param expectedValue the expected value
+     * @param newValue the new value
+     * @return the witness value, which will be the same as the
+     * expected value if successful
+     * @since 9
+     */
+    public final V compareAndExchangeAcquire(V expectedValue, V newValue) {
+        return (V)VALUE.compareAndExchangeAcquire(this, expectedValue, newValue);
+    }
+
+    /**
+     * Atomically sets the value to {@code newValue} if the current value,
+     * referred to as the <em>witness value</em>, {@code == expectedValue},
+     * with memory effects as specified by
+     * {@link VarHandle#compareAndExchangeRelease}.
+     *
+     * @param expectedValue the expected value
+     * @param newValue the new value
+     * @return the witness value, which will be the same as the
+     * expected value if successful
+     * @since 9
+     */
+    public final V compareAndExchangeRelease(V expectedValue, V newValue) {
+        return (V)VALUE.compareAndExchangeRelease(this, expectedValue, newValue);
+    }
+
+    /**
+     * Possibly atomically sets the value to {@code newValue}
+     * if the current value {@code == expectedValue},
+     * with memory effects as specified by
+     * {@link VarHandle#weakCompareAndSet}.
+     *
+     * @param expectedValue the expected value
+     * @param newValue the new value
+     * @return {@code true} if successful
+     * @since 9
+     */
+    public final boolean weakCompareAndSetVolatile(V expectedValue, V newValue) {
+        return VALUE.weakCompareAndSet(this, expectedValue, newValue);
+    }
+
+    /**
+     * Possibly atomically sets the value to {@code newValue}
+     * if the current value {@code == expectedValue},
+     * with memory effects as specified by
+     * {@link VarHandle#weakCompareAndSetAcquire}.
+     *
+     * @param expectedValue the expected value
+     * @param newValue the new value
+     * @return {@code true} if successful
+     * @since 9
+     */
+    public final boolean weakCompareAndSetAcquire(V expectedValue, V newValue) {
+        return VALUE.weakCompareAndSetAcquire(this, expectedValue, newValue);
+    }
+
+    /**
+     * Possibly atomically sets the value to {@code newValue}
+     * if the current value {@code == expectedValue},
+     * with memory effects as specified by
+     * {@link VarHandle#weakCompareAndSetRelease}.
+     *
+     * @param expectedValue the expected value
+     * @param newValue the new value
+     * @return {@code true} if successful
+     * @since 9
+     */
+    public final boolean weakCompareAndSetRelease(V expectedValue, V newValue) {
+        return VALUE.weakCompareAndSetRelease(this, expectedValue, newValue);
+    }
+
+}

src/java.base/share/classes/java/util/concurrent/atomic/AtomicReferenceArray.java

@@ -0,0 +1,527 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent.atomic;
+
+import java.lang.invoke.MethodHandles;
+import java.lang.invoke.VarHandle;
+import java.lang.reflect.Array;
+import java.lang.reflect.Field;
+import java.util.Arrays;
+import java.util.function.BinaryOperator;
+import java.util.function.UnaryOperator;
+
+/**
+ * An array of object references in which elements may be updated
+ * atomically.  See the {@link VarHandle} specification for
+ * descriptions of the properties of atomic accesses.
+ * @since 1.5
+ * @author Doug Lea
+ * @param <E> The base class of elements held in this array
+ */
+public class AtomicReferenceArray<E> implements java.io.Serializable {
+    private static final long serialVersionUID = -6209656149925076980L;
+    private static final VarHandle AA
+        = MethodHandles.arrayElementVarHandle(Object[].class);
+    private final Object[] array; // must have exact type Object[]
+
+    /**
+     * Creates a new AtomicReferenceArray of the given length, with all
+     * elements initially null.
+     *
+     * @param length the length of the array
+     */
+    public AtomicReferenceArray(int length) {
+        array = new Object[length];
+    }
+
+    /**
+     * Creates a new AtomicReferenceArray with the same length as, and
+     * all elements copied from, the given array.
+     *
+     * @param array the array to copy elements from
+     * @throws NullPointerException if array is null
+     */
+    public AtomicReferenceArray(E[] array) {
+        // Visibility guaranteed by final field guarantees
+        this.array = Arrays.copyOf(array, array.length, Object[].class);
+    }
+
+    /**
+     * Returns the length of the array.
+     *
+     * @return the length of the array
+     */
+    public final int length() {
+        return array.length;
+    }
+
+    /**
+     * Returns the current value of the element at index {@code i},
+     * with memory effects as specified by {@link VarHandle#getVolatile}.
+     *
+     * @param i the index
+     * @return the current value
+     */
+    @SuppressWarnings("unchecked")
+    public final E get(int i) {
+        return (E)AA.getVolatile(array, i);
+    }
+
+    /**
+     * Sets the element at index {@code i} to {@code newValue},
+     * with memory effects as specified by {@link VarHandle#setVolatile}.
+     *
+     * @param i the index
+     * @param newValue the new value
+     */
+    public final void set(int i, E newValue) {
+        AA.setVolatile(array, i, newValue);
+    }
+
+    /**
+     * Sets the element at index {@code i} to {@code newValue},
+     * with memory effects as specified by {@link VarHandle#setRelease}.
+     *
+     * @param i the index
+     * @param newValue the new value
+     * @since 1.6
+     */
+    public final void lazySet(int i, E newValue) {
+        AA.setRelease(array, i, newValue);
+    }
+
+    /**
+     * Atomically sets the element at index {@code i} to {@code
+     * newValue} and returns the old value,
+     * with memory effects as specified by {@link VarHandle#getAndSet}.
+     *
+     * @param i the index
+     * @param newValue the new value
+     * @return the previous value
+     */
+    @SuppressWarnings("unchecked")
+    public final E getAndSet(int i, E newValue) {
+        return (E)AA.getAndSet(array, i, newValue);
+    }
+
+    /**
+     * Atomically sets the element at index {@code i} to {@code newValue}
+     * if the element's current value {@code == expectedValue},
+     * with memory effects as specified by {@link VarHandle#compareAndSet}.
+     *
+     * @param i the index
+     * @param expectedValue the expected value
+     * @param newValue the new value
+     * @return {@code true} if successful. False return indicates that
+     * the actual value was not equal to the expected value.
+     */
+    public final boolean compareAndSet(int i, E expectedValue, E newValue) {
+        return AA.compareAndSet(array, i, expectedValue, newValue);
+    }
+
+    /**
+     * Possibly atomically sets the element at index {@code i} to
+     * {@code newValue} if the element's current value {@code == expectedValue},
+     * with memory effects as specified by {@link VarHandle#weakCompareAndSetPlain}.
+     *
+     * @deprecated This method has plain memory effects but the method
+     * name implies volatile memory effects (see methods such as
+     * {@link #compareAndExchange} and {@link #compareAndSet}).  To avoid
+     * confusion over plain or volatile memory effects it is recommended that
+     * the method {@link #weakCompareAndSetPlain} be used instead.
+     *
+     * @param i the index
+     * @param expectedValue the expected value
+     * @param newValue the new value
+     * @return {@code true} if successful
+     * @see #weakCompareAndSetPlain
+     */
+    @Deprecated(since="9")
+    public final boolean weakCompareAndSet(int i, E expectedValue, E newValue) {
+        return AA.weakCompareAndSetPlain(array, i, expectedValue, newValue);
+    }
+
+    /**
+     * Possibly atomically sets the element at index {@code i} to
+     * {@code newValue} if the element's current value {@code == expectedValue},
+     * with memory effects as specified by {@link VarHandle#weakCompareAndSetPlain}.
+     *
+     * @param i the index
+     * @param expectedValue the expected value
+     * @param newValue the new value
+     * @return {@code true} if successful
+     * @since 9
+     */
+    public final boolean weakCompareAndSetPlain(int i, E expectedValue, E newValue) {
+        return AA.weakCompareAndSetPlain(array, i, expectedValue, newValue);
+    }
+
+    /**
+     * Atomically updates (with memory effects as specified by {@link
+     * VarHandle#compareAndSet}) the element at index {@code i} with
+     * the results of applying the given function, returning the
+     * previous value. The function should be side-effect-free, since
+     * it may be re-applied when attempted updates fail due to
+     * contention among threads.
+     *
+     * @param i the index
+     * @param updateFunction a side-effect-free function
+     * @return the previous value
+     * @since 1.8
+     */
+    public final E getAndUpdate(int i, UnaryOperator<E> updateFunction) {
+        E prev = get(i), next = null;
+        for (boolean haveNext = false;;) {
+            if (!haveNext)
+                next = updateFunction.apply(prev);
+            if (weakCompareAndSetVolatile(i, prev, next))
+                return prev;
+            haveNext = (prev == (prev = get(i)));
+        }
+    }
+
+    /**
+     * Atomically updates (with memory effects as specified by {@link
+     * VarHandle#compareAndSet}) the element at index {@code i} with
+     * the results of applying the given function, returning the
+     * updated value. The function should be side-effect-free, since it
+     * may be re-applied when attempted updates fail due to contention
+     * among threads.
+     *
+     * @param i the index
+     * @param updateFunction a side-effect-free function
+     * @return the updated value
+     * @since 1.8
+     */
+    public final E updateAndGet(int i, UnaryOperator<E> updateFunction) {
+        E prev = get(i), next = null;
+        for (boolean haveNext = false;;) {
+            if (!haveNext)
+                next = updateFunction.apply(prev);
+            if (weakCompareAndSetVolatile(i, prev, next))
+                return next;
+            haveNext = (prev == (prev = get(i)));
+        }
+    }
+
+    /**
+     * Atomically updates (with memory effects as specified by {@link
+     * VarHandle#compareAndSet}) the element at index {@code i} with
+     * the results of applying the given function to the current and
+     * given values, returning the previous value. The function should
+     * be side-effect-free, since it may be re-applied when attempted
+     * updates fail due to contention among threads.  The function is
+     * applied with the current value of the element at index {@code i}
+     * as its first argument, and the given update as the second
+     * argument.
+     *
+     * @param i the index
+     * @param x the update value
+     * @param accumulatorFunction a side-effect-free function of two arguments
+     * @return the previous value
+     * @since 1.8
+     */
+    public final E getAndAccumulate(int i, E x,
+                                    BinaryOperator<E> accumulatorFunction) {
+        E prev = get(i), next = null;
+        for (boolean haveNext = false;;) {
+            if (!haveNext)
+                next = accumulatorFunction.apply(prev, x);
+            if (weakCompareAndSetVolatile(i, prev, next))
+                return prev;
+            haveNext = (prev == (prev = get(i)));
+        }
+    }
+
+    /**
+     * Atomically updates (with memory effects as specified by {@link
+     * VarHandle#compareAndSet}) the element at index {@code i} with
+     * the results of applying the given function to the current and
+     * given values, returning the updated value. The function should
+     * be side-effect-free, since it may be re-applied when attempted
+     * updates fail due to contention among threads.  The function is
+     * applied with the current value of the element at index {@code i}
+     * as its first argument, and the given update as the second
+     * argument.
+     *
+     * @param i the index
+     * @param x the update value
+     * @param accumulatorFunction a side-effect-free function of two arguments
+     * @return the updated value
+     * @since 1.8
+     */
+    public final E accumulateAndGet(int i, E x,
+                                    BinaryOperator<E> accumulatorFunction) {
+        E prev = get(i), next = null;
+        for (boolean haveNext = false;;) {
+            if (!haveNext)
+                next = accumulatorFunction.apply(prev, x);
+            if (weakCompareAndSetVolatile(i, prev, next))
+                return next;
+            haveNext = (prev == (prev = get(i)));
+        }
+    }
+
+    /**
+     * Returns the String representation of the current values of array.
+     * @return the String representation of the current values of array
+     */
+    public String toString() {
+        int iMax = array.length - 1;
+        if (iMax == -1)
+            return "[]";
+
+        StringBuilder b = new StringBuilder();
+        b.append('[');
+        for (int i = 0; ; i++) {
+            b.append(get(i));
+            if (i == iMax)
+                return b.append(']').toString();
+            b.append(',').append(' ');
+        }
+    }
+
+    /**
+     * Reconstitutes the instance from a stream (that is, deserializes it).
+     * @param s the stream
+     * @throws ClassNotFoundException if the class of a serialized object
+     *         could not be found
+     * @throws java.io.IOException if an I/O error occurs
+     */
+    private void readObject(java.io.ObjectInputStream s)
+        throws java.io.IOException, ClassNotFoundException {
+        // Note: This must be changed if any additional fields are defined
+        Object a = s.readFields().get("array", null);
+        if (a == null || !a.getClass().isArray())
+            throw new java.io.InvalidObjectException("Not array type");
+        if (a.getClass() != Object[].class)
+            a = Arrays.copyOf((Object[])a, Array.getLength(a), Object[].class);
+        Field arrayField = java.security.AccessController.doPrivileged(
+            (java.security.PrivilegedAction<Field>) () -> {
+                try {
+                    Field f = AtomicReferenceArray.class
+                        .getDeclaredField("array");
+                    f.setAccessible(true);
+                    return f;
+                } catch (ReflectiveOperationException e) {
+                    throw new Error(e);
+                }});
+        try {
+            arrayField.set(this, a);
+        } catch (IllegalAccessException e) {
+            throw new Error(e);
+        }
+    }
+
+    // jdk9
+
+    /**
+     * Returns the current value of the element at index {@code i},
+     * with memory semantics of reading as if the variable was declared
+     * non-{@code volatile}.
+     *
+     * @param i the index
+     * @return the value
+     * @since 9
+     */
+    public final E getPlain(int i) {
+        return (E)AA.get(array, i);
+    }
+
+    /**
+     * Sets the element at index {@code i} to {@code newValue},
+     * with memory semantics of setting as if the variable was
+     * declared non-{@code volatile} and non-{@code final}.
+     *
+     * @param i the index
+     * @param newValue the new value
+     * @since 9
+     */
+    public final void setPlain(int i, E newValue) {
+        AA.set(array, i, newValue);
+    }
+
+    /**
+     * Returns the current value of the element at index {@code i},
+     * with memory effects as specified by {@link VarHandle#getOpaque}.
+     *
+     * @param i the index
+     * @return the value
+     * @since 9
+     */
+    public final E getOpaque(int i) {
+        return (E)AA.getOpaque(array, i);
+    }
+
+    /**
+     * Sets the element at index {@code i} to {@code newValue},
+     * with memory effects as specified by {@link VarHandle#setOpaque}.
+     *
+     * @param i the index
+     * @param newValue the new value
+     * @since 9
+     */
+    public final void setOpaque(int i, E newValue) {
+        AA.setOpaque(array, i, newValue);
+    }
+
+    /**
+     * Returns the current value of the element at index {@code i},
+     * with memory effects as specified by {@link VarHandle#getAcquire}.
+     *
+     * @param i the index
+     * @return the value
+     * @since 9
+     */
+    public final E getAcquire(int i) {
+        return (E)AA.getAcquire(array, i);
+    }
+
+    /**
+     * Sets the element at index {@code i} to {@code newValue},
+     * with memory effects as specified by {@link VarHandle#setRelease}.
+     *
+     * @param i the index
+     * @param newValue the new value
+     * @since 9
+     */
+    public final void setRelease(int i, E newValue) {
+        AA.setRelease(array, i, newValue);
+    }
+
+    /**
+     * Atomically sets the element at index {@code i} to {@code newValue}
+     * if the element's current value, referred to as the <em>witness
+     * value</em>, {@code == expectedValue},
+     * with memory effects as specified by
+     * {@link VarHandle#compareAndExchange}.
+     *
+     * @param i the index
+     * @param expectedValue the expected value
+     * @param newValue the new value
+     * @return the witness value, which will be the same as the
+     * expected value if successful
+     * @since 9
+     */
+    public final E compareAndExchange(int i, E expectedValue, E newValue) {
+        return (E)AA.compareAndExchange(array, i, expectedValue, newValue);
+    }
+
+    /**
+     * Atomically sets the element at index {@code i} to {@code newValue}
+     * if the element's current value, referred to as the <em>witness
+     * value</em>, {@code == expectedValue},
+     * with memory effects as specified by
+     * {@link VarHandle#compareAndExchangeAcquire}.
+     *
+     * @param i the index
+     * @param expectedValue the expected value
+     * @param newValue the new value
+     * @return the witness value, which will be the same as the
+     * expected value if successful
+     * @since 9
+     */
+    public final E compareAndExchangeAcquire(int i, E expectedValue, E newValue) {
+        return (E)AA.compareAndExchangeAcquire(array, i, expectedValue, newValue);
+    }
+
+    /**
+     * Atomically sets the element at index {@code i} to {@code newValue}
+     * if the element's current value, referred to as the <em>witness
+     * value</em>, {@code == expectedValue},
+     * with memory effects as specified by
+     * {@link VarHandle#compareAndExchangeRelease}.
+     *
+     * @param i the index
+     * @param expectedValue the expected value
+     * @param newValue the new value
+     * @return the witness value, which will be the same as the
+     * expected value if successful
+     * @since 9
+     */
+    public final E compareAndExchangeRelease(int i, E expectedValue, E newValue) {
+        return (E)AA.compareAndExchangeRelease(array, i, expectedValue, newValue);
+    }
+
+    /**
+     * Possibly atomically sets the element at index {@code i} to
+     * {@code newValue} if the element's current value {@code == expectedValue},
+     * with memory effects as specified by
+     * {@link VarHandle#weakCompareAndSet}.
+     *
+     * @param i the index
+     * @param expectedValue the expected value
+     * @param newValue the new value
+     * @return {@code true} if successful
+     * @since 9
+     */
+    public final boolean weakCompareAndSetVolatile(int i, E expectedValue, E newValue) {
+        return AA.weakCompareAndSet(array, i, expectedValue, newValue);
+    }
+
+    /**
+     * Possibly atomically sets the element at index {@code i} to
+     * {@code newValue} if the element's current value {@code == expectedValue},
+     * with memory effects as specified by
+     * {@link VarHandle#weakCompareAndSetAcquire}.
+     *
+     * @param i the index
+     * @param expectedValue the expected value
+     * @param newValue the new value
+     * @return {@code true} if successful
+     * @since 9
+     */
+    public final boolean weakCompareAndSetAcquire(int i, E expectedValue, E newValue) {
+        return AA.weakCompareAndSetAcquire(array, i, expectedValue, newValue);
+    }
+
+    /**
+     * Possibly atomically sets the element at index {@code i} to
+     * {@code newValue} if the element's current value {@code == expectedValue},
+     * with memory effects as specified by
+     * {@link VarHandle#weakCompareAndSetRelease}.
+     *
+     * @param i the index
+     * @param expectedValue the expected value
+     * @param newValue the new value
+     * @return {@code true} if successful
+     * @since 9
+     */
+    public final boolean weakCompareAndSetRelease(int i, E expectedValue, E newValue) {
+        return AA.weakCompareAndSetRelease(array, i, expectedValue, newValue);
+    }
+
+}

src/java.base/share/classes/java/util/concurrent/atomic/AtomicReferenceFieldUpdater.java

@@ -0,0 +1,477 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent.atomic;
+
+import java.lang.reflect.Field;
+import java.lang.reflect.Modifier;
+import java.security.AccessController;
+import java.security.PrivilegedActionException;
+import java.security.PrivilegedExceptionAction;
+import java.util.Objects;
+import java.util.function.BinaryOperator;
+import java.util.function.UnaryOperator;
+import jdk.internal.misc.Unsafe;
+import jdk.internal.reflect.CallerSensitive;
+import jdk.internal.reflect.Reflection;
+import java.lang.invoke.VarHandle;
+
+/**
+ * A reflection-based utility that enables atomic updates to
+ * designated {@code volatile} reference fields of designated
+ * classes.  This class is designed for use in atomic data structures
+ * in which several reference fields of the same node are
+ * independently subject to atomic updates. For example, a tree node
+ * might be declared as
+ *
+ * <pre> {@code
+ * class Node {
+ *   private volatile Node left, right;
+ *
+ *   private static final AtomicReferenceFieldUpdater<Node, Node> leftUpdater =
+ *     AtomicReferenceFieldUpdater.newUpdater(Node.class, Node.class, "left");
+ *   private static AtomicReferenceFieldUpdater<Node, Node> rightUpdater =
+ *     AtomicReferenceFieldUpdater.newUpdater(Node.class, Node.class, "right");
+ *
+ *   Node getLeft() { return left; }
+ *   boolean compareAndSetLeft(Node expect, Node update) {
+ *     return leftUpdater.compareAndSet(this, expect, update);
+ *   }
+ *   // ... and so on
+ * }}</pre>
+ *
+ * <p>Note that the guarantees of the {@code compareAndSet}
+ * method in this class are weaker than in other atomic classes.
+ * Because this class cannot ensure that all uses of the field
+ * are appropriate for purposes of atomic access, it can
+ * guarantee atomicity only with respect to other invocations of
+ * {@code compareAndSet} and {@code set} on the same updater.
+ *
+ * <p>Object arguments for parameters of type {@code T} that are not
+ * instances of the class passed to {@link #newUpdater} will result in
+ * a {@link ClassCastException} being thrown.
+ *
+ * @since 1.5
+ * @author Doug Lea
+ * @param <T> The type of the object holding the updatable field
+ * @param <V> The type of the field
+ */
+public abstract class AtomicReferenceFieldUpdater<T,V> {
+
+    /**
+     * Creates and returns an updater for objects with the given field.
+     * The Class arguments are needed to check that reflective types and
+     * generic types match.
+     *
+     * @param tclass the class of the objects holding the field
+     * @param vclass the class of the field
+     * @param fieldName the name of the field to be updated
+     * @param <U> the type of instances of tclass
+     * @param <W> the type of instances of vclass
+     * @return the updater
+     * @throws ClassCastException if the field is of the wrong type
+     * @throws IllegalArgumentException if the field is not volatile
+     * @throws RuntimeException with a nested reflection-based
+     * exception if the class does not hold field or is the wrong type,
+     * or the field is inaccessible to the caller according to Java language
+     * access control
+     */
+    @CallerSensitive
+    public static <U,W> AtomicReferenceFieldUpdater<U,W> newUpdater(Class<U> tclass,
+                                                                    Class<W> vclass,
+                                                                    String fieldName) {
+        return new AtomicReferenceFieldUpdaterImpl<U,W>
+            (tclass, vclass, fieldName, Reflection.getCallerClass());
+    }
+
+    /**
+     * Protected do-nothing constructor for use by subclasses.
+     */
+    protected AtomicReferenceFieldUpdater() {
+    }
+
+    /**
+     * Atomically sets the field of the given object managed by this updater
+     * to the given updated value if the current value {@code ==} the
+     * expected value. This method is guaranteed to be atomic with respect to
+     * other calls to {@code compareAndSet} and {@code set}, but not
+     * necessarily with respect to other changes in the field.
+     *
+     * @param obj An object whose field to conditionally set
+     * @param expect the expected value
+     * @param update the new value
+     * @return {@code true} if successful
+     */
+    public abstract boolean compareAndSet(T obj, V expect, V update);
+
+    /**
+     * Atomically sets the field of the given object managed by this updater
+     * to the given updated value if the current value {@code ==} the
+     * expected value. This method is guaranteed to be atomic with respect to
+     * other calls to {@code compareAndSet} and {@code set}, but not
+     * necessarily with respect to other changes in the field.
+     *
+     * <p><a href="package-summary.html#weakCompareAndSet">May fail
+     * spuriously and does not provide ordering guarantees</a>, so is
+     * only rarely an appropriate alternative to {@code compareAndSet}.
+     *
+     * @param obj An object whose field to conditionally set
+     * @param expect the expected value
+     * @param update the new value
+     * @return {@code true} if successful
+     */
+    public abstract boolean weakCompareAndSet(T obj, V expect, V update);
+
+    /**
+     * Sets the field of the given object managed by this updater to the
+     * given updated value. This operation is guaranteed to act as a volatile
+     * store with respect to subsequent invocations of {@code compareAndSet}.
+     *
+     * @param obj An object whose field to set
+     * @param newValue the new value
+     */
+    public abstract void set(T obj, V newValue);
+
+    /**
+     * Eventually sets the field of the given object managed by this
+     * updater to the given updated value.
+     *
+     * @param obj An object whose field to set
+     * @param newValue the new value
+     * @since 1.6
+     */
+    public abstract void lazySet(T obj, V newValue);
+
+    /**
+     * Returns the current value held in the field of the given object
+     * managed by this updater.
+     *
+     * @param obj An object whose field to get
+     * @return the current value
+     */
+    public abstract V get(T obj);
+
+    /**
+     * Atomically sets the field of the given object managed by this updater
+     * to the given value and returns the old value.
+     *
+     * @param obj An object whose field to get and set
+     * @param newValue the new value
+     * @return the previous value
+     */
+    public V getAndSet(T obj, V newValue) {
+        V prev;
+        do {
+            prev = get(obj);
+        } while (!compareAndSet(obj, prev, newValue));
+        return prev;
+    }
+
+    /**
+     * Atomically updates (with memory effects as specified by {@link
+     * VarHandle#compareAndSet}) the field of the given object managed
+     * by this updater with the results of applying the given
+     * function, returning the previous value. The function should be
+     * side-effect-free, since it may be re-applied when attempted
+     * updates fail due to contention among threads.
+     *
+     * @param obj An object whose field to get and set
+     * @param updateFunction a side-effect-free function
+     * @return the previous value
+     * @since 1.8
+     */
+    public final V getAndUpdate(T obj, UnaryOperator<V> updateFunction) {
+        V prev, next;
+        do {
+            prev = get(obj);
+            next = updateFunction.apply(prev);
+        } while (!compareAndSet(obj, prev, next));
+        return prev;
+    }
+
+    /**
+     * Atomically updates (with memory effects as specified by {@link
+     * VarHandle#compareAndSet}) the field of the given object managed
+     * by this updater with the results of applying the given
+     * function, returning the updated value. The function should be
+     * side-effect-free, since it may be re-applied when attempted
+     * updates fail due to contention among threads.
+     *
+     * @param obj An object whose field to get and set
+     * @param updateFunction a side-effect-free function
+     * @return the updated value
+     * @since 1.8
+     */
+    public final V updateAndGet(T obj, UnaryOperator<V> updateFunction) {
+        V prev, next;
+        do {
+            prev = get(obj);
+            next = updateFunction.apply(prev);
+        } while (!compareAndSet(obj, prev, next));
+        return next;
+    }
+
+    /**
+     * Atomically updates (with memory effects as specified by {@link
+     * VarHandle#compareAndSet}) the field of the given object managed
+     * by this updater with the results of applying the given function
+     * to the current and given values, returning the previous value.
+     * The function should be side-effect-free, since it may be
+     * re-applied when attempted updates fail due to contention among
+     * threads.  The function is applied with the current value as its
+     * first argument, and the given update as the second argument.
+     *
+     * @param obj An object whose field to get and set
+     * @param x the update value
+     * @param accumulatorFunction a side-effect-free function of two arguments
+     * @return the previous value
+     * @since 1.8
+     */
+    public final V getAndAccumulate(T obj, V x,
+                                    BinaryOperator<V> accumulatorFunction) {
+        V prev, next;
+        do {
+            prev = get(obj);
+            next = accumulatorFunction.apply(prev, x);
+        } while (!compareAndSet(obj, prev, next));
+        return prev;
+    }
+
+    /**
+     * Atomically updates (with memory effects as specified by {@link
+     * VarHandle#compareAndSet}) the field of the given object managed
+     * by this updater with the results of applying the given function
+     * to the current and given values, returning the updated value.
+     * The function should be side-effect-free, since it may be
+     * re-applied when attempted updates fail due to contention among
+     * threads.  The function is applied with the current value as its
+     * first argument, and the given update as the second argument.
+     *
+     * @param obj An object whose field to get and set
+     * @param x the update value
+     * @param accumulatorFunction a side-effect-free function of two arguments
+     * @return the updated value
+     * @since 1.8
+     */
+    public final V accumulateAndGet(T obj, V x,
+                                    BinaryOperator<V> accumulatorFunction) {
+        V prev, next;
+        do {
+            prev = get(obj);
+            next = accumulatorFunction.apply(prev, x);
+        } while (!compareAndSet(obj, prev, next));
+        return next;
+    }
+
+    private static final class AtomicReferenceFieldUpdaterImpl<T,V>
+        extends AtomicReferenceFieldUpdater<T,V> {
+        private static final Unsafe U = Unsafe.getUnsafe();
+        private final long offset;
+        /**
+         * if field is protected, the subclass constructing updater, else
+         * the same as tclass
+         */
+        private final Class<?> cclass;
+        /** class holding the field */
+        private final Class<T> tclass;
+        /** field value type */
+        private final Class<V> vclass;
+
+        /*
+         * Internal type checks within all update methods contain
+         * internal inlined optimizations checking for the common
+         * cases where the class is final (in which case a simple
+         * getClass comparison suffices) or is of type Object (in
+         * which case no check is needed because all objects are
+         * instances of Object). The Object case is handled simply by
+         * setting vclass to null in constructor.  The targetCheck and
+         * updateCheck methods are invoked when these faster
+         * screenings fail.
+         */
+
+        AtomicReferenceFieldUpdaterImpl(final Class<T> tclass,
+                                        final Class<V> vclass,
+                                        final String fieldName,
+                                        final Class<?> caller) {
+            final Field field;
+            final Class<?> fieldClass;
+            final int modifiers;
+            try {
+                field = AccessController.doPrivileged(
+                    new PrivilegedExceptionAction<Field>() {
+                        public Field run() throws NoSuchFieldException {
+                            return tclass.getDeclaredField(fieldName);
+                        }
+                    });
+                modifiers = field.getModifiers();
+                sun.reflect.misc.ReflectUtil.ensureMemberAccess(
+                    caller, tclass, null, modifiers);
+                ClassLoader cl = tclass.getClassLoader();
+                ClassLoader ccl = caller.getClassLoader();
+                if ((ccl != null) && (ccl != cl) &&
+                    ((cl == null) || !isAncestor(cl, ccl))) {
+                    sun.reflect.misc.ReflectUtil.checkPackageAccess(tclass);
+                }
+                fieldClass = field.getType();
+            } catch (PrivilegedActionException pae) {
+                throw new RuntimeException(pae.getException());
+            } catch (Exception ex) {
+                throw new RuntimeException(ex);
+            }
+
+            if (vclass != fieldClass)
+                throw new ClassCastException();
+            if (vclass.isPrimitive())
+                throw new IllegalArgumentException("Must be reference type");
+
+            if (!Modifier.isVolatile(modifiers))
+                throw new IllegalArgumentException("Must be volatile type");
+
+            // Access to protected field members is restricted to receivers only
+            // of the accessing class, or one of its subclasses, and the
+            // accessing class must in turn be a subclass (or package sibling)
+            // of the protected member's defining class.
+            // If the updater refers to a protected field of a declaring class
+            // outside the current package, the receiver argument will be
+            // narrowed to the type of the accessing class.
+            this.cclass = (Modifier.isProtected(modifiers) &&
+                           tclass.isAssignableFrom(caller) &&
+                           !isSamePackage(tclass, caller))
+                          ? caller : tclass;
+            this.tclass = tclass;
+            this.vclass = vclass;
+            this.offset = U.objectFieldOffset(field);
+        }
+
+        /**
+         * Returns true if the second classloader can be found in the first
+         * classloader's delegation chain.
+         * Equivalent to the inaccessible: first.isAncestor(second).
+         */
+        private static boolean isAncestor(ClassLoader first, ClassLoader second) {
+            ClassLoader acl = first;
+            do {
+                acl = acl.getParent();
+                if (second == acl) {
+                    return true;
+                }
+            } while (acl != null);
+            return false;
+        }
+
+        /**
+         * Returns true if the two classes have the same class loader and
+         * package qualifier
+         */
+        private static boolean isSamePackage(Class<?> class1, Class<?> class2) {
+            return class1.getClassLoader() == class2.getClassLoader()
+                   && Objects.equals(class1.getPackageName(), class2.getPackageName());
+        }
+
+        /**
+         * Checks that target argument is instance of cclass.  On
+         * failure, throws cause.
+         */
+        private final void accessCheck(T obj) {
+            if (!cclass.isInstance(obj))
+                throwAccessCheckException(obj);
+        }
+
+        /**
+         * Throws access exception if accessCheck failed due to
+         * protected access, else ClassCastException.
+         */
+        private final void throwAccessCheckException(T obj) {
+            if (cclass == tclass)
+                throw new ClassCastException();
+            else
+                throw new RuntimeException(
+                    new IllegalAccessException(
+                        "Class " +
+                        cclass.getName() +
+                        " can not access a protected member of class " +
+                        tclass.getName() +
+                        " using an instance of " +
+                        obj.getClass().getName()));
+        }
+
+        private final void valueCheck(V v) {
+            if (v != null && !(vclass.isInstance(v)))
+                throwCCE();
+        }
+
+        static void throwCCE() {
+            throw new ClassCastException();
+        }
+
+        public final boolean compareAndSet(T obj, V expect, V update) {
+            accessCheck(obj);
+            valueCheck(update);
+            return U.compareAndSetObject(obj, offset, expect, update);
+        }
+
+        public final boolean weakCompareAndSet(T obj, V expect, V update) {
+            // same implementation as strong form for now
+            accessCheck(obj);
+            valueCheck(update);
+            return U.compareAndSetObject(obj, offset, expect, update);
+        }
+
+        public final void set(T obj, V newValue) {
+            accessCheck(obj);
+            valueCheck(newValue);
+            U.putObjectVolatile(obj, offset, newValue);
+        }
+
+        public final void lazySet(T obj, V newValue) {
+            accessCheck(obj);
+            valueCheck(newValue);
+            U.putObjectRelease(obj, offset, newValue);
+        }
+
+        @SuppressWarnings("unchecked")
+        public final V get(T obj) {
+            accessCheck(obj);
+            return (V)U.getObjectVolatile(obj, offset);
+        }
+
+        @SuppressWarnings("unchecked")
+        public final V getAndSet(T obj, V newValue) {
+            accessCheck(obj);
+            valueCheck(newValue);
+            return (V)U.getAndSetObject(obj, offset, newValue);
+        }
+    }
+}

src/java.base/share/classes/java/util/concurrent/atomic/AtomicStampedReference.java

@@ -0,0 +1,209 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent.atomic;
+
+import java.lang.invoke.MethodHandles;
+import java.lang.invoke.VarHandle;
+
+/**
+ * An {@code AtomicStampedReference} maintains an object reference
+ * along with an integer "stamp", that can be updated atomically.
+ *
+ * <p>Implementation note: This implementation maintains stamped
+ * references by creating internal objects representing "boxed"
+ * [reference, integer] pairs.
+ *
+ * @since 1.5
+ * @author Doug Lea
+ * @param <V> The type of object referred to by this reference
+ */
+public class AtomicStampedReference<V> {
+
+    private static class Pair<T> {
+        final T reference;
+        final int stamp;
+        private Pair(T reference, int stamp) {
+            this.reference = reference;
+            this.stamp = stamp;
+        }
+        static <T> Pair<T> of(T reference, int stamp) {
+            return new Pair<T>(reference, stamp);
+        }
+    }
+
+    private volatile Pair<V> pair;
+
+    /**
+     * Creates a new {@code AtomicStampedReference} with the given
+     * initial values.
+     *
+     * @param initialRef the initial reference
+     * @param initialStamp the initial stamp
+     */
+    public AtomicStampedReference(V initialRef, int initialStamp) {
+        pair = Pair.of(initialRef, initialStamp);
+    }
+
+    /**
+     * Returns the current value of the reference.
+     *
+     * @return the current value of the reference
+     */
+    public V getReference() {
+        return pair.reference;
+    }
+
+    /**
+     * Returns the current value of the stamp.
+     *
+     * @return the current value of the stamp
+     */
+    public int getStamp() {
+        return pair.stamp;
+    }
+
+    /**
+     * Returns the current values of both the reference and the stamp.
+     * Typical usage is {@code int[1] holder; ref = v.get(holder); }.
+     *
+     * @param stampHolder an array of size of at least one.  On return,
+     * {@code stampHolder[0]} will hold the value of the stamp.
+     * @return the current value of the reference
+     */
+    public V get(int[] stampHolder) {
+        Pair<V> pair = this.pair;
+        stampHolder[0] = pair.stamp;
+        return pair.reference;
+    }
+
+    /**
+     * Atomically sets the value of both the reference and stamp
+     * to the given update values if the
+     * current reference is {@code ==} to the expected reference
+     * and the current stamp is equal to the expected stamp.
+     *
+     * <p><a href="package-summary.html#weakCompareAndSet">May fail
+     * spuriously and does not provide ordering guarantees</a>, so is
+     * only rarely an appropriate alternative to {@code compareAndSet}.
+     *
+     * @param expectedReference the expected value of the reference
+     * @param newReference the new value for the reference
+     * @param expectedStamp the expected value of the stamp
+     * @param newStamp the new value for the stamp
+     * @return {@code true} if successful
+     */
+    public boolean weakCompareAndSet(V   expectedReference,
+                                     V   newReference,
+                                     int expectedStamp,
+                                     int newStamp) {
+        return compareAndSet(expectedReference, newReference,
+                             expectedStamp, newStamp);
+    }
+
+    /**
+     * Atomically sets the value of both the reference and stamp
+     * to the given update values if the
+     * current reference is {@code ==} to the expected reference
+     * and the current stamp is equal to the expected stamp.
+     *
+     * @param expectedReference the expected value of the reference
+     * @param newReference the new value for the reference
+     * @param expectedStamp the expected value of the stamp
+     * @param newStamp the new value for the stamp
+     * @return {@code true} if successful
+     */
+    public boolean compareAndSet(V   expectedReference,
+                                 V   newReference,
+                                 int expectedStamp,
+                                 int newStamp) {
+        Pair<V> current = pair;
+        return
+            expectedReference == current.reference &&
+            expectedStamp == current.stamp &&
+            ((newReference == current.reference &&
+              newStamp == current.stamp) ||
+             casPair(current, Pair.of(newReference, newStamp)));
+    }
+
+    /**
+     * Unconditionally sets the value of both the reference and stamp.
+     *
+     * @param newReference the new value for the reference
+     * @param newStamp the new value for the stamp
+     */
+    public void set(V newReference, int newStamp) {
+        Pair<V> current = pair;
+        if (newReference != current.reference || newStamp != current.stamp)
+            this.pair = Pair.of(newReference, newStamp);
+    }
+
+    /**
+     * Atomically sets the value of the stamp to the given update value
+     * if the current reference is {@code ==} to the expected
+     * reference.  Any given invocation of this operation may fail
+     * (return {@code false}) spuriously, but repeated invocation
+     * when the current value holds the expected value and no other
+     * thread is also attempting to set the value will eventually
+     * succeed.
+     *
+     * @param expectedReference the expected value of the reference
+     * @param newStamp the new value for the stamp
+     * @return {@code true} if successful
+     */
+    public boolean attemptStamp(V expectedReference, int newStamp) {
+        Pair<V> current = pair;
+        return
+            expectedReference == current.reference &&
+            (newStamp == current.stamp ||
+             casPair(current, Pair.of(expectedReference, newStamp)));
+    }
+
+    // VarHandle mechanics
+    private static final VarHandle PAIR;
+    static {
+        try {
+            MethodHandles.Lookup l = MethodHandles.lookup();
+            PAIR = l.findVarHandle(AtomicStampedReference.class, "pair",
+                                   Pair.class);
+        } catch (ReflectiveOperationException e) {
+            throw new Error(e);
+        }
+    }
+
+    private boolean casPair(Pair<V> cmp, Pair<V> val) {
+        return PAIR.compareAndSet(this, cmp, val);
+    }
+}

src/java.base/share/classes/java/util/concurrent/atomic/DoubleAccumulator.java

@@ -0,0 +1,305 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent.atomic;
+
+import static java.lang.Double.doubleToRawLongBits;
+import static java.lang.Double.longBitsToDouble;
+
+import java.io.Serializable;
+import java.util.function.DoubleBinaryOperator;
+
+/**
+ * One or more variables that together maintain a running {@code double}
+ * value updated using a supplied function.  When updates (method
+ * {@link #accumulate}) are contended across threads, the set of variables
+ * may grow dynamically to reduce contention.  Method {@link #get}
+ * (or, equivalently, {@link #doubleValue}) returns the current value
+ * across the variables maintaining updates.
+ *
+ * <p>This class is usually preferable to alternatives when multiple
+ * threads update a common value that is used for purposes such as
+ * summary statistics that are frequently updated but less frequently
+ * read.
+ *
+ * <p>The supplied accumulator function should be side-effect-free,
+ * since it may be re-applied when attempted updates fail due to
+ * contention among threads.  For predictable results, the accumulator
+ * function should be commutative and associative within the floating
+ * point tolerance required in usage contexts. The function is applied
+ * with an existing value (or identity) as one argument, and a given
+ * update as the other argument. For example, to maintain a running
+ * maximum value, you could supply {@code Double::max} along with
+ * {@code Double.NEGATIVE_INFINITY} as the identity. The order of
+ * accumulation within or across threads is not guaranteed. Thus, this
+ * class may not be applicable if numerical stability is required,
+ * especially when combining values of substantially different orders
+ * of magnitude.
+ *
+ * <p>Class {@link DoubleAdder} provides analogs of the functionality
+ * of this class for the common special case of maintaining sums.  The
+ * call {@code new DoubleAdder()} is equivalent to {@code new
+ * DoubleAccumulator((x, y) -> x + y, 0.0)}.
+ *
+ * <p>This class extends {@link Number}, but does <em>not</em> define
+ * methods such as {@code equals}, {@code hashCode} and {@code
+ * compareTo} because instances are expected to be mutated, and so are
+ * not useful as collection keys.
+ *
+ * @since 1.8
+ * @author Doug Lea
+ */
+public class DoubleAccumulator extends Striped64 implements Serializable {
+    private static final long serialVersionUID = 7249069246863182397L;
+
+    private final DoubleBinaryOperator function;
+    private final long identity; // use long representation
+
+    /**
+     * Creates a new instance using the given accumulator function
+     * and identity element.
+     * @param accumulatorFunction a side-effect-free function of two arguments
+     * @param identity identity (initial value) for the accumulator function
+     */
+    public DoubleAccumulator(DoubleBinaryOperator accumulatorFunction,
+                             double identity) {
+        this.function = accumulatorFunction;
+        base = this.identity = doubleToRawLongBits(identity);
+    }
+
+    /**
+     * Updates with the given value.
+     *
+     * @param x the value
+     */
+    public void accumulate(double x) {
+        Cell[] as; long b, v, r; int m; Cell a;
+        if ((as = cells) != null
+            || ((r = doubleToRawLongBits
+                (function.applyAsDouble(longBitsToDouble(b = base), x))) != b
+                && !casBase(b, r))) {
+            boolean uncontended = true;
+            if (as == null
+                || (m = as.length - 1) < 0
+                || (a = as[getProbe() & m]) == null
+                || !(uncontended =
+                     ((r = doubleToRawLongBits
+                       (function.applyAsDouble
+                        (longBitsToDouble(v = a.value), x))) == v)
+                     || a.cas(v, r)))
+                doubleAccumulate(x, function, uncontended);
+        }
+    }
+
+    /**
+     * Returns the current value.  The returned value is <em>NOT</em>
+     * an atomic snapshot; invocation in the absence of concurrent
+     * updates returns an accurate result, but concurrent updates that
+     * occur while the value is being calculated might not be
+     * incorporated.
+     *
+     * @return the current value
+     */
+    public double get() {
+        Cell[] as = cells;
+        double result = longBitsToDouble(base);
+        if (as != null) {
+            for (Cell a : as)
+                if (a != null)
+                    result = function.applyAsDouble
+                        (result, longBitsToDouble(a.value));
+        }
+        return result;
+    }
+
+    /**
+     * Resets variables maintaining updates to the identity value.
+     * This method may be a useful alternative to creating a new
+     * updater, but is only effective if there are no concurrent
+     * updates.  Because this method is intrinsically racy, it should
+     * only be used when it is known that no threads are concurrently
+     * updating.
+     */
+    public void reset() {
+        Cell[] as = cells;
+        base = identity;
+        if (as != null) {
+            for (Cell a : as)
+                if (a != null)
+                    a.reset(identity);
+        }
+    }
+
+    /**
+     * Equivalent in effect to {@link #get} followed by {@link
+     * #reset}. This method may apply for example during quiescent
+     * points between multithreaded computations.  If there are
+     * updates concurrent with this method, the returned value is
+     * <em>not</em> guaranteed to be the final value occurring before
+     * the reset.
+     *
+     * @return the value before reset
+     */
+    public double getThenReset() {
+        Cell[] as = cells;
+        double result = longBitsToDouble(base);
+        base = identity;
+        if (as != null) {
+            for (Cell a : as) {
+                if (a != null) {
+                    double v = longBitsToDouble(a.value);
+                    a.reset(identity);
+                    result = function.applyAsDouble(result, v);
+                }
+            }
+        }
+        return result;
+    }
+
+    /**
+     * Returns the String representation of the current value.
+     * @return the String representation of the current value
+     */
+    public String toString() {
+        return Double.toString(get());
+    }
+
+    /**
+     * Equivalent to {@link #get}.
+     *
+     * @return the current value
+     */
+    public double doubleValue() {
+        return get();
+    }
+
+    /**
+     * Returns the {@linkplain #get current value} as a {@code long}
+     * after a narrowing primitive conversion.
+     */
+    public long longValue() {
+        return (long)get();
+    }
+
+    /**
+     * Returns the {@linkplain #get current value} as an {@code int}
+     * after a narrowing primitive conversion.
+     */
+    public int intValue() {
+        return (int)get();
+    }
+
+    /**
+     * Returns the {@linkplain #get current value} as a {@code float}
+     * after a narrowing primitive conversion.
+     */
+    public float floatValue() {
+        return (float)get();
+    }
+
+    /**
+     * Serialization proxy, used to avoid reference to the non-public
+     * Striped64 superclass in serialized forms.
+     * @serial include
+     */
+    private static class SerializationProxy implements Serializable {
+        private static final long serialVersionUID = 7249069246863182397L;
+
+        /**
+         * The current value returned by get().
+         * @serial
+         */
+        private final double value;
+
+        /**
+         * The function used for updates.
+         * @serial
+         */
+        private final DoubleBinaryOperator function;
+
+        /**
+         * The identity value, represented as a long, as converted by
+         * {@link Double#doubleToRawLongBits}.  The original identity
+         * can be recovered using {@link Double#longBitsToDouble}.
+         * @serial
+         */
+        private final long identity;
+
+        SerializationProxy(double value,
+                           DoubleBinaryOperator function,
+                           long identity) {
+            this.value = value;
+            this.function = function;
+            this.identity = identity;
+        }
+
+        /**
+         * Returns a {@code DoubleAccumulator} object with initial state
+         * held by this proxy.
+         *
+         * @return a {@code DoubleAccumulator} object with initial state
+         * held by this proxy
+         */
+        private Object readResolve() {
+            double d = longBitsToDouble(identity);
+            DoubleAccumulator a = new DoubleAccumulator(function, d);
+            a.base = doubleToRawLongBits(value);
+            return a;
+        }
+    }
+
+    /**
+     * Returns a
+     * <a href="../../../../serialized-form.html#java.util.concurrent.atomic.DoubleAccumulator.SerializationProxy">
+     * SerializationProxy</a>
+     * representing the state of this instance.
+     *
+     * @return a {@link SerializationProxy}
+     * representing the state of this instance
+     */
+    private Object writeReplace() {
+        return new SerializationProxy(get(), function, identity);
+    }
+
+    /**
+     * @param s the stream
+     * @throws java.io.InvalidObjectException always
+     */
+    private void readObject(java.io.ObjectInputStream s)
+        throws java.io.InvalidObjectException {
+        throw new java.io.InvalidObjectException("Proxy required");
+    }
+
+}

src/java.base/share/classes/java/util/concurrent/atomic/DoubleAdder.java

@@ -0,0 +1,266 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent.atomic;
+
+import java.io.Serializable;
+
+/**
+ * One or more variables that together maintain an initially zero
+ * {@code double} sum.  When updates (method {@link #add}) are
+ * contended across threads, the set of variables may grow dynamically
+ * to reduce contention.  Method {@link #sum} (or, equivalently {@link
+ * #doubleValue}) returns the current total combined across the
+ * variables maintaining the sum. The order of accumulation within or
+ * across threads is not guaranteed. Thus, this class may not be
+ * applicable if numerical stability is required, especially when
+ * combining values of substantially different orders of magnitude.
+ *
+ * <p>This class is usually preferable to alternatives when multiple
+ * threads update a common value that is used for purposes such as
+ * summary statistics that are frequently updated but less frequently
+ * read.
+ *
+ * <p>This class extends {@link Number}, but does <em>not</em> define
+ * methods such as {@code equals}, {@code hashCode} and {@code
+ * compareTo} because instances are expected to be mutated, and so are
+ * not useful as collection keys.
+ *
+ * @since 1.8
+ * @author Doug Lea
+ */
+public class DoubleAdder extends Striped64 implements Serializable {
+    private static final long serialVersionUID = 7249069246863182397L;
+
+    /*
+     * Note that we must use "long" for underlying representations,
+     * because there is no compareAndSet for double, due to the fact
+     * that the bitwise equals used in any CAS implementation is not
+     * the same as double-precision equals.  However, we use CAS only
+     * to detect and alleviate contention, for which bitwise equals
+     * works best anyway. In principle, the long/double conversions
+     * used here should be essentially free on most platforms since
+     * they just re-interpret bits.
+     */
+
+    /**
+     * Creates a new adder with initial sum of zero.
+     */
+    public DoubleAdder() {
+    }
+
+    /**
+     * Adds the given value.
+     *
+     * @param x the value to add
+     */
+    public void add(double x) {
+        Cell[] as; long b, v; int m; Cell a;
+        if ((as = cells) != null ||
+            !casBase(b = base,
+                     Double.doubleToRawLongBits
+                     (Double.longBitsToDouble(b) + x))) {
+            boolean uncontended = true;
+            if (as == null || (m = as.length - 1) < 0 ||
+                (a = as[getProbe() & m]) == null ||
+                !(uncontended = a.cas(v = a.value,
+                                      Double.doubleToRawLongBits
+                                      (Double.longBitsToDouble(v) + x))))
+                doubleAccumulate(x, null, uncontended);
+        }
+    }
+
+    /**
+     * Returns the current sum.  The returned value is <em>NOT</em> an
+     * atomic snapshot; invocation in the absence of concurrent
+     * updates returns an accurate result, but concurrent updates that
+     * occur while the sum is being calculated might not be
+     * incorporated.  Also, because floating-point arithmetic is not
+     * strictly associative, the returned result need not be identical
+     * to the value that would be obtained in a sequential series of
+     * updates to a single variable.
+     *
+     * @return the sum
+     */
+    public double sum() {
+        Cell[] as = cells;
+        double sum = Double.longBitsToDouble(base);
+        if (as != null) {
+            for (Cell a : as)
+                if (a != null)
+                    sum += Double.longBitsToDouble(a.value);
+        }
+        return sum;
+    }
+
+    /**
+     * Resets variables maintaining the sum to zero.  This method may
+     * be a useful alternative to creating a new adder, but is only
+     * effective if there are no concurrent updates.  Because this
+     * method is intrinsically racy, it should only be used when it is
+     * known that no threads are concurrently updating.
+     */
+    public void reset() {
+        Cell[] as = cells;
+        base = 0L; // relies on fact that double 0 must have same rep as long
+        if (as != null) {
+            for (Cell a : as)
+                if (a != null)
+                    a.reset();
+        }
+    }
+
+    /**
+     * Equivalent in effect to {@link #sum} followed by {@link
+     * #reset}. This method may apply for example during quiescent
+     * points between multithreaded computations.  If there are
+     * updates concurrent with this method, the returned value is
+     * <em>not</em> guaranteed to be the final value occurring before
+     * the reset.
+     *
+     * @return the sum
+     */
+    public double sumThenReset() {
+        Cell[] as = cells;
+        double sum = Double.longBitsToDouble(base);
+        base = 0L;
+        if (as != null) {
+            for (Cell a : as) {
+                if (a != null) {
+                    long v = a.value;
+                    a.reset();
+                    sum += Double.longBitsToDouble(v);
+                }
+            }
+        }
+        return sum;
+    }
+
+    /**
+     * Returns the String representation of the {@link #sum}.
+     * @return the String representation of the {@link #sum}
+     */
+    public String toString() {
+        return Double.toString(sum());
+    }
+
+    /**
+     * Equivalent to {@link #sum}.
+     *
+     * @return the sum
+     */
+    public double doubleValue() {
+        return sum();
+    }
+
+    /**
+     * Returns the {@link #sum} as a {@code long} after a
+     * narrowing primitive conversion.
+     */
+    public long longValue() {
+        return (long)sum();
+    }
+
+    /**
+     * Returns the {@link #sum} as an {@code int} after a
+     * narrowing primitive conversion.
+     */
+    public int intValue() {
+        return (int)sum();
+    }
+
+    /**
+     * Returns the {@link #sum} as a {@code float}
+     * after a narrowing primitive conversion.
+     */
+    public float floatValue() {
+        return (float)sum();
+    }
+
+    /**
+     * Serialization proxy, used to avoid reference to the non-public
+     * Striped64 superclass in serialized forms.
+     * @serial include
+     */
+    private static class SerializationProxy implements Serializable {
+        private static final long serialVersionUID = 7249069246863182397L;
+
+        /**
+         * The current value returned by sum().
+         * @serial
+         */
+        private final double value;
+
+        SerializationProxy(DoubleAdder a) {
+            value = a.sum();
+        }
+
+        /**
+         * Returns a {@code DoubleAdder} object with initial state
+         * held by this proxy.
+         *
+         * @return a {@code DoubleAdder} object with initial state
+         * held by this proxy
+         */
+        private Object readResolve() {
+            DoubleAdder a = new DoubleAdder();
+            a.base = Double.doubleToRawLongBits(value);
+            return a;
+        }
+    }
+
+    /**
+     * Returns a
+     * <a href="../../../../serialized-form.html#java.util.concurrent.atomic.DoubleAdder.SerializationProxy">
+     * SerializationProxy</a>
+     * representing the state of this instance.
+     *
+     * @return a {@link SerializationProxy}
+     * representing the state of this instance
+     */
+    private Object writeReplace() {
+        return new SerializationProxy(this);
+    }
+
+    /**
+     * @param s the stream
+     * @throws java.io.InvalidObjectException always
+     */
+    private void readObject(java.io.ObjectInputStream s)
+        throws java.io.InvalidObjectException {
+        throw new java.io.InvalidObjectException("Proxy required");
+    }
+
+}

src/java.base/share/classes/java/util/concurrent/atomic/LongAccumulator.java

@@ -0,0 +1,296 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent.atomic;
+
+import java.io.Serializable;
+import java.util.function.LongBinaryOperator;
+
+/**
+ * One or more variables that together maintain a running {@code long}
+ * value updated using a supplied function.  When updates (method
+ * {@link #accumulate}) are contended across threads, the set of variables
+ * may grow dynamically to reduce contention.  Method {@link #get}
+ * (or, equivalently, {@link #longValue}) returns the current value
+ * across the variables maintaining updates.
+ *
+ * <p>This class is usually preferable to {@link AtomicLong} when
+ * multiple threads update a common value that is used for purposes such
+ * as collecting statistics, not for fine-grained synchronization
+ * control.  Under low update contention, the two classes have similar
+ * characteristics. But under high contention, expected throughput of
+ * this class is significantly higher, at the expense of higher space
+ * consumption.
+ *
+ * <p>The order of accumulation within or across threads is not
+ * guaranteed and cannot be depended upon, so this class is only
+ * applicable to functions for which the order of accumulation does
+ * not matter. The supplied accumulator function should be
+ * side-effect-free, since it may be re-applied when attempted updates
+ * fail due to contention among threads. For predictable results, the
+ * accumulator function should be associative and commutative. The
+ * function is applied with an existing value (or identity) as one
+ * argument, and a given update as the other argument.  For example,
+ * to maintain a running maximum value, you could supply {@code
+ * Long::max} along with {@code Long.MIN_VALUE} as the identity.
+ *
+ * <p>Class {@link LongAdder} provides analogs of the functionality of
+ * this class for the common special case of maintaining counts and
+ * sums.  The call {@code new LongAdder()} is equivalent to {@code new
+ * LongAccumulator((x, y) -> x + y, 0L)}.
+ *
+ * <p>This class extends {@link Number}, but does <em>not</em> define
+ * methods such as {@code equals}, {@code hashCode} and {@code
+ * compareTo} because instances are expected to be mutated, and so are
+ * not useful as collection keys.
+ *
+ * @since 1.8
+ * @author Doug Lea
+ */
+public class LongAccumulator extends Striped64 implements Serializable {
+    private static final long serialVersionUID = 7249069246863182397L;
+
+    private final LongBinaryOperator function;
+    private final long identity;
+
+    /**
+     * Creates a new instance using the given accumulator function
+     * and identity element.
+     * @param accumulatorFunction a side-effect-free function of two arguments
+     * @param identity identity (initial value) for the accumulator function
+     */
+    public LongAccumulator(LongBinaryOperator accumulatorFunction,
+                           long identity) {
+        this.function = accumulatorFunction;
+        base = this.identity = identity;
+    }
+
+    /**
+     * Updates with the given value.
+     *
+     * @param x the value
+     */
+    public void accumulate(long x) {
+        Cell[] as; long b, v, r; int m; Cell a;
+        if ((as = cells) != null
+            || ((r = function.applyAsLong(b = base, x)) != b
+                && !casBase(b, r))) {
+            boolean uncontended = true;
+            if (as == null
+                || (m = as.length - 1) < 0
+                || (a = as[getProbe() & m]) == null
+                || !(uncontended =
+                     (r = function.applyAsLong(v = a.value, x)) == v
+                     || a.cas(v, r)))
+                longAccumulate(x, function, uncontended);
+        }
+    }
+
+    /**
+     * Returns the current value.  The returned value is <em>NOT</em>
+     * an atomic snapshot; invocation in the absence of concurrent
+     * updates returns an accurate result, but concurrent updates that
+     * occur while the value is being calculated might not be
+     * incorporated.
+     *
+     * @return the current value
+     */
+    public long get() {
+        Cell[] as = cells;
+        long result = base;
+        if (as != null) {
+            for (Cell a : as)
+                if (a != null)
+                    result = function.applyAsLong(result, a.value);
+        }
+        return result;
+    }
+
+    /**
+     * Resets variables maintaining updates to the identity value.
+     * This method may be a useful alternative to creating a new
+     * updater, but is only effective if there are no concurrent
+     * updates.  Because this method is intrinsically racy, it should
+     * only be used when it is known that no threads are concurrently
+     * updating.
+     */
+    public void reset() {
+        Cell[] as = cells;
+        base = identity;
+        if (as != null) {
+            for (Cell a : as)
+                if (a != null)
+                    a.reset(identity);
+        }
+    }
+
+    /**
+     * Equivalent in effect to {@link #get} followed by {@link
+     * #reset}. This method may apply for example during quiescent
+     * points between multithreaded computations.  If there are
+     * updates concurrent with this method, the returned value is
+     * <em>not</em> guaranteed to be the final value occurring before
+     * the reset.
+     *
+     * @return the value before reset
+     */
+    public long getThenReset() {
+        Cell[] as = cells;
+        long result = base;
+        base = identity;
+        if (as != null) {
+            for (Cell a : as) {
+                if (a != null) {
+                    long v = a.value;
+                    a.reset(identity);
+                    result = function.applyAsLong(result, v);
+                }
+            }
+        }
+        return result;
+    }
+
+    /**
+     * Returns the String representation of the current value.
+     * @return the String representation of the current value
+     */
+    public String toString() {
+        return Long.toString(get());
+    }
+
+    /**
+     * Equivalent to {@link #get}.
+     *
+     * @return the current value
+     */
+    public long longValue() {
+        return get();
+    }
+
+    /**
+     * Returns the {@linkplain #get current value} as an {@code int}
+     * after a narrowing primitive conversion.
+     */
+    public int intValue() {
+        return (int)get();
+    }
+
+    /**
+     * Returns the {@linkplain #get current value} as a {@code float}
+     * after a widening primitive conversion.
+     */
+    public float floatValue() {
+        return (float)get();
+    }
+
+    /**
+     * Returns the {@linkplain #get current value} as a {@code double}
+     * after a widening primitive conversion.
+     */
+    public double doubleValue() {
+        return (double)get();
+    }
+
+    /**
+     * Serialization proxy, used to avoid reference to the non-public
+     * Striped64 superclass in serialized forms.
+     * @serial include
+     */
+    private static class SerializationProxy implements Serializable {
+        private static final long serialVersionUID = 7249069246863182397L;
+
+        /**
+         * The current value returned by get().
+         * @serial
+         */
+        private final long value;
+
+        /**
+         * The function used for updates.
+         * @serial
+         */
+        private final LongBinaryOperator function;
+
+        /**
+         * The identity value.
+         * @serial
+         */
+        private final long identity;
+
+        SerializationProxy(long value,
+                           LongBinaryOperator function,
+                           long identity) {
+            this.value = value;
+            this.function = function;
+            this.identity = identity;
+        }
+
+        /**
+         * Returns a {@code LongAccumulator} object with initial state
+         * held by this proxy.
+         *
+         * @return a {@code LongAccumulator} object with initial state
+         * held by this proxy
+         */
+        private Object readResolve() {
+            LongAccumulator a = new LongAccumulator(function, identity);
+            a.base = value;
+            return a;
+        }
+    }
+
+    /**
+     * Returns a
+     * <a href="../../../../serialized-form.html#java.util.concurrent.atomic.LongAccumulator.SerializationProxy">
+     * SerializationProxy</a>
+     * representing the state of this instance.
+     *
+     * @return a {@link SerializationProxy}
+     * representing the state of this instance
+     */
+    private Object writeReplace() {
+        return new SerializationProxy(get(), function, identity);
+    }
+
+    /**
+     * @param s the stream
+     * @throws java.io.InvalidObjectException always
+     */
+    private void readObject(java.io.ObjectInputStream s)
+        throws java.io.InvalidObjectException {
+        throw new java.io.InvalidObjectException("Proxy required");
+    }
+
+}

src/java.base/share/classes/java/util/concurrent/atomic/LongAdder.java

@@ -0,0 +1,267 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent.atomic;
+
+import java.io.Serializable;
+
+/**
+ * One or more variables that together maintain an initially zero
+ * {@code long} sum.  When updates (method {@link #add}) are contended
+ * across threads, the set of variables may grow dynamically to reduce
+ * contention. Method {@link #sum} (or, equivalently, {@link
+ * #longValue}) returns the current total combined across the
+ * variables maintaining the sum.
+ *
+ * <p>This class is usually preferable to {@link AtomicLong} when
+ * multiple threads update a common sum that is used for purposes such
+ * as collecting statistics, not for fine-grained synchronization
+ * control.  Under low update contention, the two classes have similar
+ * characteristics. But under high contention, expected throughput of
+ * this class is significantly higher, at the expense of higher space
+ * consumption.
+ *
+ * <p>LongAdders can be used with a {@link
+ * java.util.concurrent.ConcurrentHashMap} to maintain a scalable
+ * frequency map (a form of histogram or multiset). For example, to
+ * add a count to a {@code ConcurrentHashMap<String,LongAdder> freqs},
+ * initializing if not already present, you can use {@code
+ * freqs.computeIfAbsent(key, k -> new LongAdder()).increment();}
+ *
+ * <p>This class extends {@link Number}, but does <em>not</em> define
+ * methods such as {@code equals}, {@code hashCode} and {@code
+ * compareTo} because instances are expected to be mutated, and so are
+ * not useful as collection keys.
+ *
+ * @since 1.8
+ * @author Doug Lea
+ */
+public class LongAdder extends Striped64 implements Serializable {
+    private static final long serialVersionUID = 7249069246863182397L;
+
+    /**
+     * Creates a new adder with initial sum of zero.
+     */
+    public LongAdder() {
+    }
+
+    /**
+     * Adds the given value.
+     *
+     * @param x the value to add
+     */
+    public void add(long x) {
+        Cell[] as; long b, v; int m; Cell a;
+        if ((as = cells) != null || !casBase(b = base, b + x)) {
+            boolean uncontended = true;
+            if (as == null || (m = as.length - 1) < 0 ||
+                (a = as[getProbe() & m]) == null ||
+                !(uncontended = a.cas(v = a.value, v + x)))
+                longAccumulate(x, null, uncontended);
+        }
+    }
+
+    /**
+     * Equivalent to {@code add(1)}.
+     */
+    public void increment() {
+        add(1L);
+    }
+
+    /**
+     * Equivalent to {@code add(-1)}.
+     */
+    public void decrement() {
+        add(-1L);
+    }
+
+    /**
+     * Returns the current sum.  The returned value is <em>NOT</em> an
+     * atomic snapshot; invocation in the absence of concurrent
+     * updates returns an accurate result, but concurrent updates that
+     * occur while the sum is being calculated might not be
+     * incorporated.
+     *
+     * @return the sum
+     */
+    public long sum() {
+        Cell[] as = cells;
+        long sum = base;
+        if (as != null) {
+            for (Cell a : as)
+                if (a != null)
+                    sum += a.value;
+        }
+        return sum;
+    }
+
+    /**
+     * Resets variables maintaining the sum to zero.  This method may
+     * be a useful alternative to creating a new adder, but is only
+     * effective if there are no concurrent updates.  Because this
+     * method is intrinsically racy, it should only be used when it is
+     * known that no threads are concurrently updating.
+     */
+    public void reset() {
+        Cell[] as = cells;
+        base = 0L;
+        if (as != null) {
+            for (Cell a : as)
+                if (a != null)
+                    a.reset();
+        }
+    }
+
+    /**
+     * Equivalent in effect to {@link #sum} followed by {@link
+     * #reset}. This method may apply for example during quiescent
+     * points between multithreaded computations.  If there are
+     * updates concurrent with this method, the returned value is
+     * <em>not</em> guaranteed to be the final value occurring before
+     * the reset.
+     *
+     * @return the sum
+     */
+    public long sumThenReset() {
+        Cell[] as = cells;
+        long sum = base;
+        base = 0L;
+        if (as != null) {
+            for (Cell a : as) {
+                if (a != null) {
+                    sum += a.value;
+                    a.reset();
+                }
+            }
+        }
+        return sum;
+    }
+
+    /**
+     * Returns the String representation of the {@link #sum}.
+     * @return the String representation of the {@link #sum}
+     */
+    public String toString() {
+        return Long.toString(sum());
+    }
+
+    /**
+     * Equivalent to {@link #sum}.
+     *
+     * @return the sum
+     */
+    public long longValue() {
+        return sum();
+    }
+
+    /**
+     * Returns the {@link #sum} as an {@code int} after a narrowing
+     * primitive conversion.
+     */
+    public int intValue() {
+        return (int)sum();
+    }
+
+    /**
+     * Returns the {@link #sum} as a {@code float}
+     * after a widening primitive conversion.
+     */
+    public float floatValue() {
+        return (float)sum();
+    }
+
+    /**
+     * Returns the {@link #sum} as a {@code double} after a widening
+     * primitive conversion.
+     */
+    public double doubleValue() {
+        return (double)sum();
+    }
+
+    /**
+     * Serialization proxy, used to avoid reference to the non-public
+     * Striped64 superclass in serialized forms.
+     * @serial include
+     */
+    private static class SerializationProxy implements Serializable {
+        private static final long serialVersionUID = 7249069246863182397L;
+
+        /**
+         * The current value returned by sum().
+         * @serial
+         */
+        private final long value;
+
+        SerializationProxy(LongAdder a) {
+            value = a.sum();
+        }
+
+        /**
+         * Returns a {@code LongAdder} object with initial state
+         * held by this proxy.
+         *
+         * @return a {@code LongAdder} object with initial state
+         * held by this proxy
+         */
+        private Object readResolve() {
+            LongAdder a = new LongAdder();
+            a.base = value;
+            return a;
+        }
+    }
+
+    /**
+     * Returns a
+     * <a href="../../../../serialized-form.html#java.util.concurrent.atomic.LongAdder.SerializationProxy">
+     * SerializationProxy</a>
+     * representing the state of this instance.
+     *
+     * @return a {@link SerializationProxy}
+     * representing the state of this instance
+     */
+    private Object writeReplace() {
+        return new SerializationProxy(this);
+    }
+
+    /**
+     * @param s the stream
+     * @throws java.io.InvalidObjectException always
+     */
+    private void readObject(java.io.ObjectInputStream s)
+        throws java.io.InvalidObjectException {
+        throw new java.io.InvalidObjectException("Proxy required");
+    }
+
+}

src/java.base/share/classes/java/util/concurrent/atomic/Striped64.java

@@ -0,0 +1,402 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent.atomic;
+
+import java.lang.invoke.MethodHandles;
+import java.lang.invoke.VarHandle;
+import java.util.Arrays;
+import java.util.concurrent.ThreadLocalRandom;
+import java.util.function.DoubleBinaryOperator;
+import java.util.function.LongBinaryOperator;
+
+/**
+ * A package-local class holding common representation and mechanics
+ * for classes supporting dynamic striping on 64bit values. The class
+ * extends Number so that concrete subclasses must publicly do so.
+ */
+@SuppressWarnings("serial")
+abstract class Striped64 extends Number {
+    /*
+     * This class maintains a lazily-initialized table of atomically
+     * updated variables, plus an extra "base" field. The table size
+     * is a power of two. Indexing uses masked per-thread hash codes.
+     * Nearly all declarations in this class are package-private,
+     * accessed directly by subclasses.
+     *
+     * Table entries are of class Cell; a variant of AtomicLong padded
+     * (via @Contended) to reduce cache contention. Padding is
+     * overkill for most Atomics because they are usually irregularly
+     * scattered in memory and thus don't interfere much with each
+     * other. But Atomic objects residing in arrays will tend to be
+     * placed adjacent to each other, and so will most often share
+     * cache lines (with a huge negative performance impact) without
+     * this precaution.
+     *
+     * In part because Cells are relatively large, we avoid creating
+     * them until they are needed.  When there is no contention, all
+     * updates are made to the base field.  Upon first contention (a
+     * failed CAS on base update), the table is initialized to size 2.
+     * The table size is doubled upon further contention until
+     * reaching the nearest power of two greater than or equal to the
+     * number of CPUS. Table slots remain empty (null) until they are
+     * needed.
+     *
+     * A single spinlock ("cellsBusy") is used for initializing and
+     * resizing the table, as well as populating slots with new Cells.
+     * There is no need for a blocking lock; when the lock is not
+     * available, threads try other slots (or the base).  During these
+     * retries, there is increased contention and reduced locality,
+     * which is still better than alternatives.
+     *
+     * The Thread probe fields maintained via ThreadLocalRandom serve
+     * as per-thread hash codes. We let them remain uninitialized as
+     * zero (if they come in this way) until they contend at slot
+     * 0. They are then initialized to values that typically do not
+     * often conflict with others.  Contention and/or table collisions
+     * are indicated by failed CASes when performing an update
+     * operation. Upon a collision, if the table size is less than
+     * the capacity, it is doubled in size unless some other thread
+     * holds the lock. If a hashed slot is empty, and lock is
+     * available, a new Cell is created. Otherwise, if the slot
+     * exists, a CAS is tried.  Retries proceed by "double hashing",
+     * using a secondary hash (Marsaglia XorShift) to try to find a
+     * free slot.
+     *
+     * The table size is capped because, when there are more threads
+     * than CPUs, supposing that each thread were bound to a CPU,
+     * there would exist a perfect hash function mapping threads to
+     * slots that eliminates collisions. When we reach capacity, we
+     * search for this mapping by randomly varying the hash codes of
+     * colliding threads.  Because search is random, and collisions
+     * only become known via CAS failures, convergence can be slow,
+     * and because threads are typically not bound to CPUS forever,
+     * may not occur at all. However, despite these limitations,
+     * observed contention rates are typically low in these cases.
+     *
+     * It is possible for a Cell to become unused when threads that
+     * once hashed to it terminate, as well as in the case where
+     * doubling the table causes no thread to hash to it under
+     * expanded mask.  We do not try to detect or remove such cells,
+     * under the assumption that for long-running instances, observed
+     * contention levels will recur, so the cells will eventually be
+     * needed again; and for short-lived ones, it does not matter.
+     */
+
+    /**
+     * Padded variant of AtomicLong supporting only raw accesses plus CAS.
+     *
+     * JVM intrinsics note: It would be possible to use a release-only
+     * form of CAS here, if it were provided.
+     */
+    @jdk.internal.vm.annotation.Contended static final class Cell {
+        volatile long value;
+        Cell(long x) { value = x; }
+        final boolean cas(long cmp, long val) {
+            return VALUE.compareAndSet(this, cmp, val);
+        }
+        final void reset() {
+            VALUE.setVolatile(this, 0L);
+        }
+        final void reset(long identity) {
+            VALUE.setVolatile(this, identity);
+        }
+
+        // VarHandle mechanics
+        private static final VarHandle VALUE;
+        static {
+            try {
+                MethodHandles.Lookup l = MethodHandles.lookup();
+                VALUE = l.findVarHandle(Cell.class, "value", long.class);
+            } catch (ReflectiveOperationException e) {
+                throw new Error(e);
+            }
+        }
+    }
+
+    /** Number of CPUS, to place bound on table size */
+    static final int NCPU = Runtime.getRuntime().availableProcessors();
+
+    /**
+     * Table of cells. When non-null, size is a power of 2.
+     */
+    transient volatile Cell[] cells;
+
+    /**
+     * Base value, used mainly when there is no contention, but also as
+     * a fallback during table initialization races. Updated via CAS.
+     */
+    transient volatile long base;
+
+    /**
+     * Spinlock (locked via CAS) used when resizing and/or creating Cells.
+     */
+    transient volatile int cellsBusy;
+
+    /**
+     * Package-private default constructor.
+     */
+    Striped64() {
+    }
+
+    /**
+     * CASes the base field.
+     */
+    final boolean casBase(long cmp, long val) {
+        return BASE.compareAndSet(this, cmp, val);
+    }
+
+    /**
+     * CASes the cellsBusy field from 0 to 1 to acquire lock.
+     */
+    final boolean casCellsBusy() {
+        return CELLSBUSY.compareAndSet(this, 0, 1);
+    }
+
+    /**
+     * Returns the probe value for the current thread.
+     * Duplicated from ThreadLocalRandom because of packaging restrictions.
+     */
+    static final int getProbe() {
+        return (int) THREAD_PROBE.get(Thread.currentThread());
+    }
+
+    /**
+     * Pseudo-randomly advances and records the given probe value for the
+     * given thread.
+     * Duplicated from ThreadLocalRandom because of packaging restrictions.
+     */
+    static final int advanceProbe(int probe) {
+        probe ^= probe << 13;   // xorshift
+        probe ^= probe >>> 17;
+        probe ^= probe << 5;
+        THREAD_PROBE.set(Thread.currentThread(), probe);
+        return probe;
+    }
+
+    /**
+     * Handles cases of updates involving initialization, resizing,
+     * creating new Cells, and/or contention. See above for
+     * explanation. This method suffers the usual non-modularity
+     * problems of optimistic retry code, relying on rechecked sets of
+     * reads.
+     *
+     * @param x the value
+     * @param fn the update function, or null for add (this convention
+     * avoids the need for an extra field or function in LongAdder).
+     * @param wasUncontended false if CAS failed before call
+     */
+    final void longAccumulate(long x, LongBinaryOperator fn,
+                              boolean wasUncontended) {
+        int h;
+        if ((h = getProbe()) == 0) {
+            ThreadLocalRandom.current(); // force initialization
+            h = getProbe();
+            wasUncontended = true;
+        }
+        boolean collide = false;                // True if last slot nonempty
+        done: for (;;) {
+            Cell[] as; Cell a; int n; long v;
+            if ((as = cells) != null && (n = as.length) > 0) {
+                if ((a = as[(n - 1) & h]) == null) {
+                    if (cellsBusy == 0) {       // Try to attach new Cell
+                        Cell r = new Cell(x);   // Optimistically create
+                        if (cellsBusy == 0 && casCellsBusy()) {
+                            try {               // Recheck under lock
+                                Cell[] rs; int m, j;
+                                if ((rs = cells) != null &&
+                                    (m = rs.length) > 0 &&
+                                    rs[j = (m - 1) & h] == null) {
+                                    rs[j] = r;
+                                    break done;
+                                }
+                            } finally {
+                                cellsBusy = 0;
+                            }
+                            continue;           // Slot is now non-empty
+                        }
+                    }
+                    collide = false;
+                }
+                else if (!wasUncontended)       // CAS already known to fail
+                    wasUncontended = true;      // Continue after rehash
+                else if (a.cas(v = a.value,
+                               (fn == null) ? v + x : fn.applyAsLong(v, x)))
+                    break;
+                else if (n >= NCPU || cells != as)
+                    collide = false;            // At max size or stale
+                else if (!collide)
+                    collide = true;
+                else if (cellsBusy == 0 && casCellsBusy()) {
+                    try {
+                        if (cells == as)        // Expand table unless stale
+                            cells = Arrays.copyOf(as, n << 1);
+                    } finally {
+                        cellsBusy = 0;
+                    }
+                    collide = false;
+                    continue;                   // Retry with expanded table
+                }
+                h = advanceProbe(h);
+            }
+            else if (cellsBusy == 0 && cells == as && casCellsBusy()) {
+                try {                           // Initialize table
+                    if (cells == as) {
+                        Cell[] rs = new Cell[2];
+                        rs[h & 1] = new Cell(x);
+                        cells = rs;
+                        break done;
+                    }
+                } finally {
+                    cellsBusy = 0;
+                }
+            }
+            // Fall back on using base
+            else if (casBase(v = base,
+                             (fn == null) ? v + x : fn.applyAsLong(v, x)))
+                break done;
+        }
+    }
+
+    private static long apply(DoubleBinaryOperator fn, long v, double x) {
+        double d = Double.longBitsToDouble(v);
+        d = (fn == null) ? d + x : fn.applyAsDouble(d, x);
+        return Double.doubleToRawLongBits(d);
+    }
+
+    /**
+     * Same as longAccumulate, but injecting long/double conversions
+     * in too many places to sensibly merge with long version, given
+     * the low-overhead requirements of this class. So must instead be
+     * maintained by copy/paste/adapt.
+     */
+    final void doubleAccumulate(double x, DoubleBinaryOperator fn,
+                                boolean wasUncontended) {
+        int h;
+        if ((h = getProbe()) == 0) {
+            ThreadLocalRandom.current(); // force initialization
+            h = getProbe();
+            wasUncontended = true;
+        }
+        boolean collide = false;                // True if last slot nonempty
+        done: for (;;) {
+            Cell[] as; Cell a; int n; long v;
+            if ((as = cells) != null && (n = as.length) > 0) {
+                if ((a = as[(n - 1) & h]) == null) {
+                    if (cellsBusy == 0) {       // Try to attach new Cell
+                        Cell r = new Cell(Double.doubleToRawLongBits(x));
+                        if (cellsBusy == 0 && casCellsBusy()) {
+                            try {               // Recheck under lock
+                                Cell[] rs; int m, j;
+                                if ((rs = cells) != null &&
+                                    (m = rs.length) > 0 &&
+                                    rs[j = (m - 1) & h] == null) {
+                                    rs[j] = r;
+                                    break done;
+                                }
+                            } finally {
+                                cellsBusy = 0;
+                            }
+                            continue;           // Slot is now non-empty
+                        }
+                    }
+                    collide = false;
+                }
+                else if (!wasUncontended)       // CAS already known to fail
+                    wasUncontended = true;      // Continue after rehash
+                else if (a.cas(v = a.value, apply(fn, v, x)))
+                    break;
+                else if (n >= NCPU || cells != as)
+                    collide = false;            // At max size or stale
+                else if (!collide)
+                    collide = true;
+                else if (cellsBusy == 0 && casCellsBusy()) {
+                    try {
+                        if (cells == as)        // Expand table unless stale
+                            cells = Arrays.copyOf(as, n << 1);
+                    } finally {
+                        cellsBusy = 0;
+                    }
+                    collide = false;
+                    continue;                   // Retry with expanded table
+                }
+                h = advanceProbe(h);
+            }
+            else if (cellsBusy == 0 && cells == as && casCellsBusy()) {
+                try {                           // Initialize table
+                    if (cells == as) {
+                        Cell[] rs = new Cell[2];
+                        rs[h & 1] = new Cell(Double.doubleToRawLongBits(x));
+                        cells = rs;
+                        break done;
+                    }
+                } finally {
+                    cellsBusy = 0;
+                }
+            }
+            // Fall back on using base
+            else if (casBase(v = base, apply(fn, v, x)))
+                break done;
+        }
+    }
+
+    // VarHandle mechanics
+    private static final VarHandle BASE;
+    private static final VarHandle CELLSBUSY;
+    private static final VarHandle THREAD_PROBE;
+    static {
+        try {
+            MethodHandles.Lookup l = MethodHandles.lookup();
+            BASE = l.findVarHandle(Striped64.class,
+                    "base", long.class);
+            CELLSBUSY = l.findVarHandle(Striped64.class,
+                    "cellsBusy", int.class);
+            l = java.security.AccessController.doPrivileged(
+                    new java.security.PrivilegedAction<>() {
+                        public MethodHandles.Lookup run() {
+                            try {
+                                return MethodHandles.privateLookupIn(Thread.class, MethodHandles.lookup());
+                            } catch (ReflectiveOperationException e) {
+                                throw new Error(e);
+                            }
+                        }});
+            THREAD_PROBE = l.findVarHandle(Thread.class,
+                    "threadLocalRandomProbe", int.class);
+        } catch (ReflectiveOperationException e) {
+            throw new Error(e);
+        }
+    }
+
+}

src/java.base/share/classes/java/util/concurrent/atomic/package-info.java

@@ -0,0 +1,111 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+/**
+ * A small toolkit of classes that support lock-free thread-safe
+ * programming on single variables.  Instances of Atomic classes
+ * maintain values that are accessed and updated using methods
+ * otherwise available for fields using associated atomic {@link
+ * java.lang.invoke.VarHandle} operations.
+ *
+ * <p>Instances of classes
+ * {@link java.util.concurrent.atomic.AtomicBoolean},
+ * {@link java.util.concurrent.atomic.AtomicInteger},
+ * {@link java.util.concurrent.atomic.AtomicLong}, and
+ * {@link java.util.concurrent.atomic.AtomicReference}
+ * each provide access and updates to a single variable of the
+ * corresponding type.  Each class also provides appropriate utility
+ * methods for that type.  For example, classes {@code AtomicLong} and
+ * {@code AtomicInteger} provide atomic increment methods.  One
+ * application is to generate sequence numbers, as in:
+ *
+ * <pre> {@code
+ * class Sequencer {
+ *   private final AtomicLong sequenceNumber
+ *     = new AtomicLong(0);
+ *   public long next() {
+ *     return sequenceNumber.getAndIncrement();
+ *   }
+ * }}</pre>
+ *
+ * <p>Arbitrary transformations of the contained value are provided both
+ * by low-level read-modify-write operations such as {@code compareAndSet}
+ * and by higher-level methods such as {@code getAndUpdate}.
+ *
+ * <p>These classes are not general purpose replacements for {@code
+ * java.lang.Integer} and related classes.  They do <em>not</em>
+ * define methods such as {@code equals}, {@code hashCode} and {@code
+ * compareTo}.  Because atomic variables are expected to be mutated,
+ * they are poor choices for hash table keys.
+ *
+ * <p>The
+ * {@link java.util.concurrent.atomic.AtomicIntegerArray},
+ * {@link java.util.concurrent.atomic.AtomicLongArray}, and
+ * {@link java.util.concurrent.atomic.AtomicReferenceArray} classes
+ * further extend atomic operation support to arrays of these types.
+ * These classes are also notable in providing {@code volatile} access
+ * semantics for their array elements.
+ *
+ * <p>In addition to classes representing single values and arrays,
+ * this package contains <em>Updater</em> classes that can be used to
+ * obtain {@code compareAndSet} and related operations on any selected
+ * {@code volatile} field of any selected class. These classes
+ * predate the introduction of {@link
+ * java.lang.invoke.VarHandle}, and are of more limited use.
+ * {@link java.util.concurrent.atomic.AtomicReferenceFieldUpdater},
+ * {@link java.util.concurrent.atomic.AtomicIntegerFieldUpdater}, and
+ * {@link java.util.concurrent.atomic.AtomicLongFieldUpdater} are
+ * reflection-based utilities that provide access to the associated
+ * field types.  These are mainly of use in atomic data structures in
+ * which several {@code volatile} fields of the same node (for
+ * example, the links of a tree node) are independently subject to
+ * atomic updates.  These classes enable greater flexibility in how
+ * and when to use atomic updates, at the expense of more awkward
+ * reflection-based setup, less convenient usage, and weaker
+ * guarantees.
+ *
+ * <p>The {@link java.util.concurrent.atomic.AtomicMarkableReference}
+ * class associates a single boolean with a reference.  For example, this
+ * bit might be used inside a data structure to mean that the object
+ * being referenced has logically been deleted.
+ *
+ * The {@link java.util.concurrent.atomic.AtomicStampedReference}
+ * class associates an integer value with a reference.  This may be
+ * used for example, to represent version numbers corresponding to
+ * series of updates.
+ *
+ * @since 1.5
+ */
+package java.util.concurrent.atomic;

src/java.base/share/classes/java/util/concurrent/locks/AbstractOwnableSynchronizer.java

@@ -0,0 +1,86 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent.locks;
+
+/**
+ * A synchronizer that may be exclusively owned by a thread.  This
+ * class provides a basis for creating locks and related synchronizers
+ * that may entail a notion of ownership.  The
+ * {@code AbstractOwnableSynchronizer} class itself does not manage or
+ * use this information. However, subclasses and tools may use
+ * appropriately maintained values to help control and monitor access
+ * and provide diagnostics.
+ *
+ * @since 1.6
+ * @author Doug Lea
+ */
+public abstract class AbstractOwnableSynchronizer
+    implements java.io.Serializable {
+
+    /** Use serial ID even though all fields transient. */
+    private static final long serialVersionUID = 3737899427754241961L;
+
+    /**
+     * Empty constructor for use by subclasses.
+     */
+    protected AbstractOwnableSynchronizer() { }
+
+    /**
+     * The current owner of exclusive mode synchronization.
+     */
+    private transient Thread exclusiveOwnerThread;
+
+    /**
+     * Sets the thread that currently owns exclusive access.
+     * A {@code null} argument indicates that no thread owns access.
+     * This method does not otherwise impose any synchronization or
+     * {@code volatile} field accesses.
+     * @param thread the owner thread
+     */
+    protected final void setExclusiveOwnerThread(Thread thread) {
+        exclusiveOwnerThread = thread;
+    }
+
+    /**
+     * Returns the thread last set by {@code setExclusiveOwnerThread},
+     * or {@code null} if never set.  This method does not otherwise
+     * impose any synchronization or {@code volatile} field accesses.
+     * @return the owner thread
+     */
+    protected final Thread getExclusiveOwnerThread() {
+        return exclusiveOwnerThread;
+    }
+}

src/java.base/share/classes/java/util/concurrent/locks/Condition.java

@@ -0,0 +1,486 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent.locks;
+
+import java.util.Date;
+import java.util.concurrent.TimeUnit;
+
+/**
+ * {@code Condition} factors out the {@code Object} monitor
+ * methods ({@link Object#wait() wait}, {@link Object#notify notify}
+ * and {@link Object#notifyAll notifyAll}) into distinct objects to
+ * give the effect of having multiple wait-sets per object, by
+ * combining them with the use of arbitrary {@link Lock} implementations.
+ * Where a {@code Lock} replaces the use of {@code synchronized} methods
+ * and statements, a {@code Condition} replaces the use of the Object
+ * monitor methods.
+ *
+ * <p>Conditions (also known as <em>condition queues</em> or
+ * <em>condition variables</em>) provide a means for one thread to
+ * suspend execution (to &quot;wait&quot;) until notified by another
+ * thread that some state condition may now be true.  Because access
+ * to this shared state information occurs in different threads, it
+ * must be protected, so a lock of some form is associated with the
+ * condition. The key property that waiting for a condition provides
+ * is that it <em>atomically</em> releases the associated lock and
+ * suspends the current thread, just like {@code Object.wait}.
+ *
+ * <p>A {@code Condition} instance is intrinsically bound to a lock.
+ * To obtain a {@code Condition} instance for a particular {@link Lock}
+ * instance use its {@link Lock#newCondition newCondition()} method.
+ *
+ * <p>As an example, suppose we have a bounded buffer which supports
+ * {@code put} and {@code take} methods.  If a
+ * {@code take} is attempted on an empty buffer, then the thread will block
+ * until an item becomes available; if a {@code put} is attempted on a
+ * full buffer, then the thread will block until a space becomes available.
+ * We would like to keep waiting {@code put} threads and {@code take}
+ * threads in separate wait-sets so that we can use the optimization of
+ * only notifying a single thread at a time when items or spaces become
+ * available in the buffer. This can be achieved using two
+ * {@link Condition} instances.
+ * <pre>
+ * class BoundedBuffer {
+ *   <b>final Lock lock = new ReentrantLock();</b>
+ *   final Condition notFull  = <b>lock.newCondition(); </b>
+ *   final Condition notEmpty = <b>lock.newCondition(); </b>
+ *
+ *   final Object[] items = new Object[100];
+ *   int putptr, takeptr, count;
+ *
+ *   public void put(Object x) throws InterruptedException {
+ *     <b>lock.lock();
+ *     try {</b>
+ *       while (count == items.length)
+ *         <b>notFull.await();</b>
+ *       items[putptr] = x;
+ *       if (++putptr == items.length) putptr = 0;
+ *       ++count;
+ *       <b>notEmpty.signal();</b>
+ *     <b>} finally {
+ *       lock.unlock();
+ *     }</b>
+ *   }
+ *
+ *   public Object take() throws InterruptedException {
+ *     <b>lock.lock();
+ *     try {</b>
+ *       while (count == 0)
+ *         <b>notEmpty.await();</b>
+ *       Object x = items[takeptr];
+ *       if (++takeptr == items.length) takeptr = 0;
+ *       --count;
+ *       <b>notFull.signal();</b>
+ *       return x;
+ *     <b>} finally {
+ *       lock.unlock();
+ *     }</b>
+ *   }
+ * }
+ * </pre>
+ *
+ * (The {@link java.util.concurrent.ArrayBlockingQueue} class provides
+ * this functionality, so there is no reason to implement this
+ * sample usage class.)
+ *
+ * <p>A {@code Condition} implementation can provide behavior and semantics
+ * that is
+ * different from that of the {@code Object} monitor methods, such as
+ * guaranteed ordering for notifications, or not requiring a lock to be held
+ * when performing notifications.
+ * If an implementation provides such specialized semantics then the
+ * implementation must document those semantics.
+ *
+ * <p>Note that {@code Condition} instances are just normal objects and can
+ * themselves be used as the target in a {@code synchronized} statement,
+ * and can have their own monitor {@link Object#wait wait} and
+ * {@link Object#notify notify} methods invoked.
+ * Acquiring the monitor lock of a {@code Condition} instance, or using its
+ * monitor methods, has no specified relationship with acquiring the
+ * {@link Lock} associated with that {@code Condition} or the use of its
+ * {@linkplain #await waiting} and {@linkplain #signal signalling} methods.
+ * It is recommended that to avoid confusion you never use {@code Condition}
+ * instances in this way, except perhaps within their own implementation.
+ *
+ * <p>Except where noted, passing a {@code null} value for any parameter
+ * will result in a {@link NullPointerException} being thrown.
+ *
+ * <h3>Implementation Considerations</h3>
+ *
+ * <p>When waiting upon a {@code Condition}, a &quot;<em>spurious
+ * wakeup</em>&quot; is permitted to occur, in
+ * general, as a concession to the underlying platform semantics.
+ * This has little practical impact on most application programs as a
+ * {@code Condition} should always be waited upon in a loop, testing
+ * the state predicate that is being waited for.  An implementation is
+ * free to remove the possibility of spurious wakeups but it is
+ * recommended that applications programmers always assume that they can
+ * occur and so always wait in a loop.
+ *
+ * <p>The three forms of condition waiting
+ * (interruptible, non-interruptible, and timed) may differ in their ease of
+ * implementation on some platforms and in their performance characteristics.
+ * In particular, it may be difficult to provide these features and maintain
+ * specific semantics such as ordering guarantees.
+ * Further, the ability to interrupt the actual suspension of the thread may
+ * not always be feasible to implement on all platforms.
+ *
+ * <p>Consequently, an implementation is not required to define exactly the
+ * same guarantees or semantics for all three forms of waiting, nor is it
+ * required to support interruption of the actual suspension of the thread.
+ *
+ * <p>An implementation is required to
+ * clearly document the semantics and guarantees provided by each of the
+ * waiting methods, and when an implementation does support interruption of
+ * thread suspension then it must obey the interruption semantics as defined
+ * in this interface.
+ *
+ * <p>As interruption generally implies cancellation, and checks for
+ * interruption are often infrequent, an implementation can favor responding
+ * to an interrupt over normal method return. This is true even if it can be
+ * shown that the interrupt occurred after another action that may have
+ * unblocked the thread. An implementation should document this behavior.
+ *
+ * @since 1.5
+ * @author Doug Lea
+ */
+public interface Condition {
+
+    /**
+     * Causes the current thread to wait until it is signalled or
+     * {@linkplain Thread#interrupt interrupted}.
+     *
+     * <p>The lock associated with this {@code Condition} is atomically
+     * released and the current thread becomes disabled for thread scheduling
+     * purposes and lies dormant until <em>one</em> of four things happens:
+     * <ul>
+     * <li>Some other thread invokes the {@link #signal} method for this
+     * {@code Condition} and the current thread happens to be chosen as the
+     * thread to be awakened; or
+     * <li>Some other thread invokes the {@link #signalAll} method for this
+     * {@code Condition}; or
+     * <li>Some other thread {@linkplain Thread#interrupt interrupts} the
+     * current thread, and interruption of thread suspension is supported; or
+     * <li>A &quot;<em>spurious wakeup</em>&quot; occurs.
+     * </ul>
+     *
+     * <p>In all cases, before this method can return the current thread must
+     * re-acquire the lock associated with this condition. When the
+     * thread returns it is <em>guaranteed</em> to hold this lock.
+     *
+     * <p>If the current thread:
+     * <ul>
+     * <li>has its interrupted status set on entry to this method; or
+     * <li>is {@linkplain Thread#interrupt interrupted} while waiting
+     * and interruption of thread suspension is supported,
+     * </ul>
+     * then {@link InterruptedException} is thrown and the current thread's
+     * interrupted status is cleared. It is not specified, in the first
+     * case, whether or not the test for interruption occurs before the lock
+     * is released.
+     *
+     * <p><b>Implementation Considerations</b>
+     *
+     * <p>The current thread is assumed to hold the lock associated with this
+     * {@code Condition} when this method is called.
+     * It is up to the implementation to determine if this is
+     * the case and if not, how to respond. Typically, an exception will be
+     * thrown (such as {@link IllegalMonitorStateException}) and the
+     * implementation must document that fact.
+     *
+     * <p>An implementation can favor responding to an interrupt over normal
+     * method return in response to a signal. In that case the implementation
+     * must ensure that the signal is redirected to another waiting thread, if
+     * there is one.
+     *
+     * @throws InterruptedException if the current thread is interrupted
+     *         (and interruption of thread suspension is supported)
+     */
+    void await() throws InterruptedException;
+
+    /**
+     * Causes the current thread to wait until it is signalled.
+     *
+     * <p>The lock associated with this condition is atomically
+     * released and the current thread becomes disabled for thread scheduling
+     * purposes and lies dormant until <em>one</em> of three things happens:
+     * <ul>
+     * <li>Some other thread invokes the {@link #signal} method for this
+     * {@code Condition} and the current thread happens to be chosen as the
+     * thread to be awakened; or
+     * <li>Some other thread invokes the {@link #signalAll} method for this
+     * {@code Condition}; or
+     * <li>A &quot;<em>spurious wakeup</em>&quot; occurs.
+     * </ul>
+     *
+     * <p>In all cases, before this method can return the current thread must
+     * re-acquire the lock associated with this condition. When the
+     * thread returns it is <em>guaranteed</em> to hold this lock.
+     *
+     * <p>If the current thread's interrupted status is set when it enters
+     * this method, or it is {@linkplain Thread#interrupt interrupted}
+     * while waiting, it will continue to wait until signalled. When it finally
+     * returns from this method its interrupted status will still
+     * be set.
+     *
+     * <p><b>Implementation Considerations</b>
+     *
+     * <p>The current thread is assumed to hold the lock associated with this
+     * {@code Condition} when this method is called.
+     * It is up to the implementation to determine if this is
+     * the case and if not, how to respond. Typically, an exception will be
+     * thrown (such as {@link IllegalMonitorStateException}) and the
+     * implementation must document that fact.
+     */
+    void awaitUninterruptibly();
+
+    /**
+     * Causes the current thread to wait until it is signalled or interrupted,
+     * or the specified waiting time elapses.
+     *
+     * <p>The lock associated with this condition is atomically
+     * released and the current thread becomes disabled for thread scheduling
+     * purposes and lies dormant until <em>one</em> of five things happens:
+     * <ul>
+     * <li>Some other thread invokes the {@link #signal} method for this
+     * {@code Condition} and the current thread happens to be chosen as the
+     * thread to be awakened; or
+     * <li>Some other thread invokes the {@link #signalAll} method for this
+     * {@code Condition}; or
+     * <li>Some other thread {@linkplain Thread#interrupt interrupts} the
+     * current thread, and interruption of thread suspension is supported; or
+     * <li>The specified waiting time elapses; or
+     * <li>A &quot;<em>spurious wakeup</em>&quot; occurs.
+     * </ul>
+     *
+     * <p>In all cases, before this method can return the current thread must
+     * re-acquire the lock associated with this condition. When the
+     * thread returns it is <em>guaranteed</em> to hold this lock.
+     *
+     * <p>If the current thread:
+     * <ul>
+     * <li>has its interrupted status set on entry to this method; or
+     * <li>is {@linkplain Thread#interrupt interrupted} while waiting
+     * and interruption of thread suspension is supported,
+     * </ul>
+     * then {@link InterruptedException} is thrown and the current thread's
+     * interrupted status is cleared. It is not specified, in the first
+     * case, whether or not the test for interruption occurs before the lock
+     * is released.
+     *
+     * <p>The method returns an estimate of the number of nanoseconds
+     * remaining to wait given the supplied {@code nanosTimeout}
+     * value upon return, or a value less than or equal to zero if it
+     * timed out. This value can be used to determine whether and how
+     * long to re-wait in cases where the wait returns but an awaited
+     * condition still does not hold. Typical uses of this method take
+     * the following form:
+     *
+     * <pre> {@code
+     * boolean aMethod(long timeout, TimeUnit unit) {
+     *   long nanos = unit.toNanos(timeout);
+     *   lock.lock();
+     *   try {
+     *     while (!conditionBeingWaitedFor()) {
+     *       if (nanos <= 0L)
+     *         return false;
+     *       nanos = theCondition.awaitNanos(nanos);
+     *     }
+     *     // ...
+     *   } finally {
+     *     lock.unlock();
+     *   }
+     * }}</pre>
+     *
+     * <p>Design note: This method requires a nanosecond argument so
+     * as to avoid truncation errors in reporting remaining times.
+     * Such precision loss would make it difficult for programmers to
+     * ensure that total waiting times are not systematically shorter
+     * than specified when re-waits occur.
+     *
+     * <p><b>Implementation Considerations</b>
+     *
+     * <p>The current thread is assumed to hold the lock associated with this
+     * {@code Condition} when this method is called.
+     * It is up to the implementation to determine if this is
+     * the case and if not, how to respond. Typically, an exception will be
+     * thrown (such as {@link IllegalMonitorStateException}) and the
+     * implementation must document that fact.
+     *
+     * <p>An implementation can favor responding to an interrupt over normal
+     * method return in response to a signal, or over indicating the elapse
+     * of the specified waiting time. In either case the implementation
+     * must ensure that the signal is redirected to another waiting thread, if
+     * there is one.
+     *
+     * @param nanosTimeout the maximum time to wait, in nanoseconds
+     * @return an estimate of the {@code nanosTimeout} value minus
+     *         the time spent waiting upon return from this method.
+     *         A positive value may be used as the argument to a
+     *         subsequent call to this method to finish waiting out
+     *         the desired time.  A value less than or equal to zero
+     *         indicates that no time remains.
+     * @throws InterruptedException if the current thread is interrupted
+     *         (and interruption of thread suspension is supported)
+     */
+    long awaitNanos(long nanosTimeout) throws InterruptedException;
+
+    /**
+     * Causes the current thread to wait until it is signalled or interrupted,
+     * or the specified waiting time elapses. This method is behaviorally
+     * equivalent to:
+     * <pre> {@code awaitNanos(unit.toNanos(time)) > 0}</pre>
+     *
+     * @param time the maximum time to wait
+     * @param unit the time unit of the {@code time} argument
+     * @return {@code false} if the waiting time detectably elapsed
+     *         before return from the method, else {@code true}
+     * @throws InterruptedException if the current thread is interrupted
+     *         (and interruption of thread suspension is supported)
+     */
+    boolean await(long time, TimeUnit unit) throws InterruptedException;
+
+    /**
+     * Causes the current thread to wait until it is signalled or interrupted,
+     * or the specified deadline elapses.
+     *
+     * <p>The lock associated with this condition is atomically
+     * released and the current thread becomes disabled for thread scheduling
+     * purposes and lies dormant until <em>one</em> of five things happens:
+     * <ul>
+     * <li>Some other thread invokes the {@link #signal} method for this
+     * {@code Condition} and the current thread happens to be chosen as the
+     * thread to be awakened; or
+     * <li>Some other thread invokes the {@link #signalAll} method for this
+     * {@code Condition}; or
+     * <li>Some other thread {@linkplain Thread#interrupt interrupts} the
+     * current thread, and interruption of thread suspension is supported; or
+     * <li>The specified deadline elapses; or
+     * <li>A &quot;<em>spurious wakeup</em>&quot; occurs.
+     * </ul>
+     *
+     * <p>In all cases, before this method can return the current thread must
+     * re-acquire the lock associated with this condition. When the
+     * thread returns it is <em>guaranteed</em> to hold this lock.
+     *
+     * <p>If the current thread:
+     * <ul>
+     * <li>has its interrupted status set on entry to this method; or
+     * <li>is {@linkplain Thread#interrupt interrupted} while waiting
+     * and interruption of thread suspension is supported,
+     * </ul>
+     * then {@link InterruptedException} is thrown and the current thread's
+     * interrupted status is cleared. It is not specified, in the first
+     * case, whether or not the test for interruption occurs before the lock
+     * is released.
+     *
+     * <p>The return value indicates whether the deadline has elapsed,
+     * which can be used as follows:
+     * <pre> {@code
+     * boolean aMethod(Date deadline) {
+     *   boolean stillWaiting = true;
+     *   lock.lock();
+     *   try {
+     *     while (!conditionBeingWaitedFor()) {
+     *       if (!stillWaiting)
+     *         return false;
+     *       stillWaiting = theCondition.awaitUntil(deadline);
+     *     }
+     *     // ...
+     *   } finally {
+     *     lock.unlock();
+     *   }
+     * }}</pre>
+     *
+     * <p><b>Implementation Considerations</b>
+     *
+     * <p>The current thread is assumed to hold the lock associated with this
+     * {@code Condition} when this method is called.
+     * It is up to the implementation to determine if this is
+     * the case and if not, how to respond. Typically, an exception will be
+     * thrown (such as {@link IllegalMonitorStateException}) and the
+     * implementation must document that fact.
+     *
+     * <p>An implementation can favor responding to an interrupt over normal
+     * method return in response to a signal, or over indicating the passing
+     * of the specified deadline. In either case the implementation
+     * must ensure that the signal is redirected to another waiting thread, if
+     * there is one.
+     *
+     * @param deadline the absolute time to wait until
+     * @return {@code false} if the deadline has elapsed upon return, else
+     *         {@code true}
+     * @throws InterruptedException if the current thread is interrupted
+     *         (and interruption of thread suspension is supported)
+     */
+    boolean awaitUntil(Date deadline) throws InterruptedException;
+
+    /**
+     * Wakes up one waiting thread.
+     *
+     * <p>If any threads are waiting on this condition then one
+     * is selected for waking up. That thread must then re-acquire the
+     * lock before returning from {@code await}.
+     *
+     * <p><b>Implementation Considerations</b>
+     *
+     * <p>An implementation may (and typically does) require that the
+     * current thread hold the lock associated with this {@code
+     * Condition} when this method is called. Implementations must
+     * document this precondition and any actions taken if the lock is
+     * not held. Typically, an exception such as {@link
+     * IllegalMonitorStateException} will be thrown.
+     */
+    void signal();
+
+    /**
+     * Wakes up all waiting threads.
+     *
+     * <p>If any threads are waiting on this condition then they are
+     * all woken up. Each thread must re-acquire the lock before it can
+     * return from {@code await}.
+     *
+     * <p><b>Implementation Considerations</b>
+     *
+     * <p>An implementation may (and typically does) require that the
+     * current thread hold the lock associated with this {@code
+     * Condition} when this method is called. Implementations must
+     * document this precondition and any actions taken if the lock is
+     * not held. Typically, an exception such as {@link
+     * IllegalMonitorStateException} will be thrown.
+     */
+    void signalAll();
+}

src/java.base/share/classes/java/util/concurrent/locks/Lock.java

@@ -0,0 +1,359 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent.locks;
+
+import java.util.concurrent.TimeUnit;
+
+/**
+ * {@code Lock} implementations provide more extensive locking
+ * operations than can be obtained using {@code synchronized} methods
+ * and statements.  They allow more flexible structuring, may have
+ * quite different properties, and may support multiple associated
+ * {@link Condition} objects.
+ *
+ * <p>A lock is a tool for controlling access to a shared resource by
+ * multiple threads. Commonly, a lock provides exclusive access to a
+ * shared resource: only one thread at a time can acquire the lock and
+ * all access to the shared resource requires that the lock be
+ * acquired first. However, some locks may allow concurrent access to
+ * a shared resource, such as the read lock of a {@link ReadWriteLock}.
+ *
+ * <p>The use of {@code synchronized} methods or statements provides
+ * access to the implicit monitor lock associated with every object, but
+ * forces all lock acquisition and release to occur in a block-structured way:
+ * when multiple locks are acquired they must be released in the opposite
+ * order, and all locks must be released in the same lexical scope in which
+ * they were acquired.
+ *
+ * <p>While the scoping mechanism for {@code synchronized} methods
+ * and statements makes it much easier to program with monitor locks,
+ * and helps avoid many common programming errors involving locks,
+ * there are occasions where you need to work with locks in a more
+ * flexible way. For example, some algorithms for traversing
+ * concurrently accessed data structures require the use of
+ * &quot;hand-over-hand&quot; or &quot;chain locking&quot;: you
+ * acquire the lock of node A, then node B, then release A and acquire
+ * C, then release B and acquire D and so on.  Implementations of the
+ * {@code Lock} interface enable the use of such techniques by
+ * allowing a lock to be acquired and released in different scopes,
+ * and allowing multiple locks to be acquired and released in any
+ * order.
+ *
+ * <p>With this increased flexibility comes additional
+ * responsibility. The absence of block-structured locking removes the
+ * automatic release of locks that occurs with {@code synchronized}
+ * methods and statements. In most cases, the following idiom
+ * should be used:
+ *
+ * <pre> {@code
+ * Lock l = ...;
+ * l.lock();
+ * try {
+ *   // access the resource protected by this lock
+ * } finally {
+ *   l.unlock();
+ * }}</pre>
+ *
+ * When locking and unlocking occur in different scopes, care must be
+ * taken to ensure that all code that is executed while the lock is
+ * held is protected by try-finally or try-catch to ensure that the
+ * lock is released when necessary.
+ *
+ * <p>{@code Lock} implementations provide additional functionality
+ * over the use of {@code synchronized} methods and statements by
+ * providing a non-blocking attempt to acquire a lock ({@link
+ * #tryLock()}), an attempt to acquire the lock that can be
+ * interrupted ({@link #lockInterruptibly}, and an attempt to acquire
+ * the lock that can timeout ({@link #tryLock(long, TimeUnit)}).
+ *
+ * <p>A {@code Lock} class can also provide behavior and semantics
+ * that is quite different from that of the implicit monitor lock,
+ * such as guaranteed ordering, non-reentrant usage, or deadlock
+ * detection. If an implementation provides such specialized semantics
+ * then the implementation must document those semantics.
+ *
+ * <p>Note that {@code Lock} instances are just normal objects and can
+ * themselves be used as the target in a {@code synchronized} statement.
+ * Acquiring the
+ * monitor lock of a {@code Lock} instance has no specified relationship
+ * with invoking any of the {@link #lock} methods of that instance.
+ * It is recommended that to avoid confusion you never use {@code Lock}
+ * instances in this way, except within their own implementation.
+ *
+ * <p>Except where noted, passing a {@code null} value for any
+ * parameter will result in a {@link NullPointerException} being
+ * thrown.
+ *
+ * <h3>Memory Synchronization</h3>
+ *
+ * <p>All {@code Lock} implementations <em>must</em> enforce the same
+ * memory synchronization semantics as provided by the built-in monitor
+ * lock, as described in
+ * <a href="https://docs.oracle.com/javase/specs/jls/se8/html/jls-17.html#jls-17.4">
+ * Chapter 17 of
+ * <cite>The Java&trade; Language Specification</cite></a>:
+ * <ul>
+ * <li>A successful {@code lock} operation has the same memory
+ * synchronization effects as a successful <em>Lock</em> action.
+ * <li>A successful {@code unlock} operation has the same
+ * memory synchronization effects as a successful <em>Unlock</em> action.
+ * </ul>
+ *
+ * Unsuccessful locking and unlocking operations, and reentrant
+ * locking/unlocking operations, do not require any memory
+ * synchronization effects.
+ *
+ * <h3>Implementation Considerations</h3>
+ *
+ * <p>The three forms of lock acquisition (interruptible,
+ * non-interruptible, and timed) may differ in their performance
+ * characteristics, ordering guarantees, or other implementation
+ * qualities.  Further, the ability to interrupt the <em>ongoing</em>
+ * acquisition of a lock may not be available in a given {@code Lock}
+ * class.  Consequently, an implementation is not required to define
+ * exactly the same guarantees or semantics for all three forms of
+ * lock acquisition, nor is it required to support interruption of an
+ * ongoing lock acquisition.  An implementation is required to clearly
+ * document the semantics and guarantees provided by each of the
+ * locking methods. It must also obey the interruption semantics as
+ * defined in this interface, to the extent that interruption of lock
+ * acquisition is supported: which is either totally, or only on
+ * method entry.
+ *
+ * <p>As interruption generally implies cancellation, and checks for
+ * interruption are often infrequent, an implementation can favor responding
+ * to an interrupt over normal method return. This is true even if it can be
+ * shown that the interrupt occurred after another action may have unblocked
+ * the thread. An implementation should document this behavior.
+ *
+ * @see ReentrantLock
+ * @see Condition
+ * @see ReadWriteLock
+ *
+ * @since 1.5
+ * @author Doug Lea
+ */
+public interface Lock {
+
+    /**
+     * Acquires the lock.
+     *
+     * <p>If the lock is not available then the current thread becomes
+     * disabled for thread scheduling purposes and lies dormant until the
+     * lock has been acquired.
+     *
+     * <p><b>Implementation Considerations</b>
+     *
+     * <p>A {@code Lock} implementation may be able to detect erroneous use
+     * of the lock, such as an invocation that would cause deadlock, and
+     * may throw an (unchecked) exception in such circumstances.  The
+     * circumstances and the exception type must be documented by that
+     * {@code Lock} implementation.
+     */
+    void lock();
+
+    /**
+     * Acquires the lock unless the current thread is
+     * {@linkplain Thread#interrupt interrupted}.
+     *
+     * <p>Acquires the lock if it is available and returns immediately.
+     *
+     * <p>If the lock is not available then the current thread becomes
+     * disabled for thread scheduling purposes and lies dormant until
+     * one of two things happens:
+     *
+     * <ul>
+     * <li>The lock is acquired by the current thread; or
+     * <li>Some other thread {@linkplain Thread#interrupt interrupts} the
+     * current thread, and interruption of lock acquisition is supported.
+     * </ul>
+     *
+     * <p>If the current thread:
+     * <ul>
+     * <li>has its interrupted status set on entry to this method; or
+     * <li>is {@linkplain Thread#interrupt interrupted} while acquiring the
+     * lock, and interruption of lock acquisition is supported,
+     * </ul>
+     * then {@link InterruptedException} is thrown and the current thread's
+     * interrupted status is cleared.
+     *
+     * <p><b>Implementation Considerations</b>
+     *
+     * <p>The ability to interrupt a lock acquisition in some
+     * implementations may not be possible, and if possible may be an
+     * expensive operation.  The programmer should be aware that this
+     * may be the case. An implementation should document when this is
+     * the case.
+     *
+     * <p>An implementation can favor responding to an interrupt over
+     * normal method return.
+     *
+     * <p>A {@code Lock} implementation may be able to detect
+     * erroneous use of the lock, such as an invocation that would
+     * cause deadlock, and may throw an (unchecked) exception in such
+     * circumstances.  The circumstances and the exception type must
+     * be documented by that {@code Lock} implementation.
+     *
+     * @throws InterruptedException if the current thread is
+     *         interrupted while acquiring the lock (and interruption
+     *         of lock acquisition is supported)
+     */
+    void lockInterruptibly() throws InterruptedException;
+
+    /**
+     * Acquires the lock only if it is free at the time of invocation.
+     *
+     * <p>Acquires the lock if it is available and returns immediately
+     * with the value {@code true}.
+     * If the lock is not available then this method will return
+     * immediately with the value {@code false}.
+     *
+     * <p>A typical usage idiom for this method would be:
+     * <pre> {@code
+     * Lock lock = ...;
+     * if (lock.tryLock()) {
+     *   try {
+     *     // manipulate protected state
+     *   } finally {
+     *     lock.unlock();
+     *   }
+     * } else {
+     *   // perform alternative actions
+     * }}</pre>
+     *
+     * This usage ensures that the lock is unlocked if it was acquired, and
+     * doesn't try to unlock if the lock was not acquired.
+     *
+     * @return {@code true} if the lock was acquired and
+     *         {@code false} otherwise
+     */
+    boolean tryLock();
+
+    /**
+     * Acquires the lock if it is free within the given waiting time and the
+     * current thread has not been {@linkplain Thread#interrupt interrupted}.
+     *
+     * <p>If the lock is available this method returns immediately
+     * with the value {@code true}.
+     * If the lock is not available then
+     * the current thread becomes disabled for thread scheduling
+     * purposes and lies dormant until one of three things happens:
+     * <ul>
+     * <li>The lock is acquired by the current thread; or
+     * <li>Some other thread {@linkplain Thread#interrupt interrupts} the
+     * current thread, and interruption of lock acquisition is supported; or
+     * <li>The specified waiting time elapses
+     * </ul>
+     *
+     * <p>If the lock is acquired then the value {@code true} is returned.
+     *
+     * <p>If the current thread:
+     * <ul>
+     * <li>has its interrupted status set on entry to this method; or
+     * <li>is {@linkplain Thread#interrupt interrupted} while acquiring
+     * the lock, and interruption of lock acquisition is supported,
+     * </ul>
+     * then {@link InterruptedException} is thrown and the current thread's
+     * interrupted status is cleared.
+     *
+     * <p>If the specified waiting time elapses then the value {@code false}
+     * is returned.
+     * If the time is
+     * less than or equal to zero, the method will not wait at all.
+     *
+     * <p><b>Implementation Considerations</b>
+     *
+     * <p>The ability to interrupt a lock acquisition in some implementations
+     * may not be possible, and if possible may
+     * be an expensive operation.
+     * The programmer should be aware that this may be the case. An
+     * implementation should document when this is the case.
+     *
+     * <p>An implementation can favor responding to an interrupt over normal
+     * method return, or reporting a timeout.
+     *
+     * <p>A {@code Lock} implementation may be able to detect
+     * erroneous use of the lock, such as an invocation that would cause
+     * deadlock, and may throw an (unchecked) exception in such circumstances.
+     * The circumstances and the exception type must be documented by that
+     * {@code Lock} implementation.
+     *
+     * @param time the maximum time to wait for the lock
+     * @param unit the time unit of the {@code time} argument
+     * @return {@code true} if the lock was acquired and {@code false}
+     *         if the waiting time elapsed before the lock was acquired
+     *
+     * @throws InterruptedException if the current thread is interrupted
+     *         while acquiring the lock (and interruption of lock
+     *         acquisition is supported)
+     */
+    boolean tryLock(long time, TimeUnit unit) throws InterruptedException;
+
+    /**
+     * Releases the lock.
+     *
+     * <p><b>Implementation Considerations</b>
+     *
+     * <p>A {@code Lock} implementation will usually impose
+     * restrictions on which thread can release a lock (typically only the
+     * holder of the lock can release it) and may throw
+     * an (unchecked) exception if the restriction is violated.
+     * Any restrictions and the exception
+     * type must be documented by that {@code Lock} implementation.
+     */
+    void unlock();
+
+    /**
+     * Returns a new {@link Condition} instance that is bound to this
+     * {@code Lock} instance.
+     *
+     * <p>Before waiting on the condition the lock must be held by the
+     * current thread.
+     * A call to {@link Condition#await()} will atomically release the lock
+     * before waiting and re-acquire the lock before the wait returns.
+     *
+     * <p><b>Implementation Considerations</b>
+     *
+     * <p>The exact operation of the {@link Condition} instance depends on
+     * the {@code Lock} implementation and must be documented by that
+     * implementation.
+     *
+     * @return A new {@link Condition} instance for this {@code Lock} instance
+     * @throws UnsupportedOperationException if this {@code Lock}
+     *         implementation does not support conditions
+     */
+    Condition newCondition();
+}

src/java.base/share/classes/java/util/concurrent/locks/LockSupport.java

@@ -0,0 +1,431 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent.locks;
+
+import jdk.internal.misc.Unsafe;
+
+/**
+ * Basic thread blocking primitives for creating locks and other
+ * synchronization classes.
+ *
+ * <p>This class associates, with each thread that uses it, a permit
+ * (in the sense of the {@link java.util.concurrent.Semaphore
+ * Semaphore} class). A call to {@code park} will return immediately
+ * if the permit is available, consuming it in the process; otherwise
+ * it <em>may</em> block.  A call to {@code unpark} makes the permit
+ * available, if it was not already available. (Unlike with Semaphores
+ * though, permits do not accumulate. There is at most one.)
+ * Reliable usage requires the use of volatile (or atomic) variables
+ * to control when to park or unpark.  Orderings of calls to these
+ * methods are maintained with respect to volatile variable accesses,
+ * but not necessarily non-volatile variable accesses.
+ *
+ * <p>Methods {@code park} and {@code unpark} provide efficient
+ * means of blocking and unblocking threads that do not encounter the
+ * problems that cause the deprecated methods {@code Thread.suspend}
+ * and {@code Thread.resume} to be unusable for such purposes: Races
+ * between one thread invoking {@code park} and another thread trying
+ * to {@code unpark} it will preserve liveness, due to the
+ * permit. Additionally, {@code park} will return if the caller's
+ * thread was interrupted, and timeout versions are supported. The
+ * {@code park} method may also return at any other time, for "no
+ * reason", so in general must be invoked within a loop that rechecks
+ * conditions upon return. In this sense {@code park} serves as an
+ * optimization of a "busy wait" that does not waste as much time
+ * spinning, but must be paired with an {@code unpark} to be
+ * effective.
+ *
+ * <p>The three forms of {@code park} each also support a
+ * {@code blocker} object parameter. This object is recorded while
+ * the thread is blocked to permit monitoring and diagnostic tools to
+ * identify the reasons that threads are blocked. (Such tools may
+ * access blockers using method {@link #getBlocker(Thread)}.)
+ * The use of these forms rather than the original forms without this
+ * parameter is strongly encouraged. The normal argument to supply as
+ * a {@code blocker} within a lock implementation is {@code this}.
+ *
+ * <p>These methods are designed to be used as tools for creating
+ * higher-level synchronization utilities, and are not in themselves
+ * useful for most concurrency control applications.  The {@code park}
+ * method is designed for use only in constructions of the form:
+ *
+ * <pre> {@code
+ * while (!canProceed()) {
+ *   // ensure request to unpark is visible to other threads
+ *   ...
+ *   LockSupport.park(this);
+ * }}</pre>
+ *
+ * where no actions by the thread publishing a request to unpark,
+ * prior to the call to {@code park}, entail locking or blocking.
+ * Because only one permit is associated with each thread, any
+ * intermediary uses of {@code park}, including implicitly via class
+ * loading, could lead to an unresponsive thread (a "lost unpark").
+ *
+ * <p><b>Sample Usage.</b> Here is a sketch of a first-in-first-out
+ * non-reentrant lock class:
+ * <pre> {@code
+ * class FIFOMutex {
+ *   private final AtomicBoolean locked = new AtomicBoolean(false);
+ *   private final Queue<Thread> waiters
+ *     = new ConcurrentLinkedQueue<>();
+ *
+ *   public void lock() {
+ *     boolean wasInterrupted = false;
+ *     // publish current thread for unparkers
+ *     waiters.add(Thread.currentThread());
+ *
+ *     // Block while not first in queue or cannot acquire lock
+ *     while (waiters.peek() != Thread.currentThread() ||
+ *            !locked.compareAndSet(false, true)) {
+ *       LockSupport.park(this);
+ *       // ignore interrupts while waiting
+ *       if (Thread.interrupted())
+ *         wasInterrupted = true;
+ *     }
+ *
+ *     waiters.remove();
+ *     // ensure correct interrupt status on return
+ *     if (wasInterrupted)
+ *       Thread.currentThread().interrupt();
+ *   }
+ *
+ *   public void unlock() {
+ *     locked.set(false);
+ *     LockSupport.unpark(waiters.peek());
+ *   }
+ *
+ *   static {
+ *     // Reduce the risk of "lost unpark" due to classloading
+ *     Class<?> ensureLoaded = LockSupport.class;
+ *   }
+ * }}</pre>
+ *
+ * @since 1.5
+ */
+public class LockSupport {
+    private LockSupport() {} // Cannot be instantiated.
+
+    private static void setBlocker(Thread t, Object arg) {
+        // Even though volatile, hotspot doesn't need a write barrier here.
+        U.putObject(t, PARKBLOCKER, arg);
+    }
+
+    /**
+     * Makes available the permit for the given thread, if it
+     * was not already available.  If the thread was blocked on
+     * {@code park} then it will unblock.  Otherwise, its next call
+     * to {@code park} is guaranteed not to block. This operation
+     * is not guaranteed to have any effect at all if the given
+     * thread has not been started.
+     *
+     * @param thread the thread to unpark, or {@code null}, in which case
+     *        this operation has no effect
+     */
+    public static void unpark(Thread thread) {
+        if (thread != null)
+            U.unpark(thread);
+    }
+
+    /**
+     * Disables the current thread for thread scheduling purposes unless the
+     * permit is available.
+     *
+     * <p>If the permit is available then it is consumed and the call returns
+     * immediately; otherwise
+     * the current thread becomes disabled for thread scheduling
+     * purposes and lies dormant until one of three things happens:
+     *
+     * <ul>
+     * <li>Some other thread invokes {@link #unpark unpark} with the
+     * current thread as the target; or
+     *
+     * <li>Some other thread {@linkplain Thread#interrupt interrupts}
+     * the current thread; or
+     *
+     * <li>The call spuriously (that is, for no reason) returns.
+     * </ul>
+     *
+     * <p>This method does <em>not</em> report which of these caused the
+     * method to return. Callers should re-check the conditions which caused
+     * the thread to park in the first place. Callers may also determine,
+     * for example, the interrupt status of the thread upon return.
+     *
+     * @param blocker the synchronization object responsible for this
+     *        thread parking
+     * @since 1.6
+     */
+    public static void park(Object blocker) {
+        Thread t = Thread.currentThread();
+        setBlocker(t, blocker);
+        U.park(false, 0L);
+        setBlocker(t, null);
+    }
+
+    /**
+     * Disables the current thread for thread scheduling purposes, for up to
+     * the specified waiting time, unless the permit is available.
+     *
+     * <p>If the permit is available then it is consumed and the call
+     * returns immediately; otherwise the current thread becomes disabled
+     * for thread scheduling purposes and lies dormant until one of four
+     * things happens:
+     *
+     * <ul>
+     * <li>Some other thread invokes {@link #unpark unpark} with the
+     * current thread as the target; or
+     *
+     * <li>Some other thread {@linkplain Thread#interrupt interrupts}
+     * the current thread; or
+     *
+     * <li>The specified waiting time elapses; or
+     *
+     * <li>The call spuriously (that is, for no reason) returns.
+     * </ul>
+     *
+     * <p>This method does <em>not</em> report which of these caused the
+     * method to return. Callers should re-check the conditions which caused
+     * the thread to park in the first place. Callers may also determine,
+     * for example, the interrupt status of the thread, or the elapsed time
+     * upon return.
+     *
+     * @param blocker the synchronization object responsible for this
+     *        thread parking
+     * @param nanos the maximum number of nanoseconds to wait
+     * @since 1.6
+     */
+    public static void parkNanos(Object blocker, long nanos) {
+        if (nanos > 0) {
+            Thread t = Thread.currentThread();
+            setBlocker(t, blocker);
+            U.park(false, nanos);
+            setBlocker(t, null);
+        }
+    }
+
+    /**
+     * Disables the current thread for thread scheduling purposes, until
+     * the specified deadline, unless the permit is available.
+     *
+     * <p>If the permit is available then it is consumed and the call
+     * returns immediately; otherwise the current thread becomes disabled
+     * for thread scheduling purposes and lies dormant until one of four
+     * things happens:
+     *
+     * <ul>
+     * <li>Some other thread invokes {@link #unpark unpark} with the
+     * current thread as the target; or
+     *
+     * <li>Some other thread {@linkplain Thread#interrupt interrupts} the
+     * current thread; or
+     *
+     * <li>The specified deadline passes; or
+     *
+     * <li>The call spuriously (that is, for no reason) returns.
+     * </ul>
+     *
+     * <p>This method does <em>not</em> report which of these caused the
+     * method to return. Callers should re-check the conditions which caused
+     * the thread to park in the first place. Callers may also determine,
+     * for example, the interrupt status of the thread, or the current time
+     * upon return.
+     *
+     * @param blocker the synchronization object responsible for this
+     *        thread parking
+     * @param deadline the absolute time, in milliseconds from the Epoch,
+     *        to wait until
+     * @since 1.6
+     */
+    public static void parkUntil(Object blocker, long deadline) {
+        Thread t = Thread.currentThread();
+        setBlocker(t, blocker);
+        U.park(true, deadline);
+        setBlocker(t, null);
+    }
+
+    /**
+     * Returns the blocker object supplied to the most recent
+     * invocation of a park method that has not yet unblocked, or null
+     * if not blocked.  The value returned is just a momentary
+     * snapshot -- the thread may have since unblocked or blocked on a
+     * different blocker object.
+     *
+     * @param t the thread
+     * @return the blocker
+     * @throws NullPointerException if argument is null
+     * @since 1.6
+     */
+    public static Object getBlocker(Thread t) {
+        if (t == null)
+            throw new NullPointerException();
+        return U.getObjectVolatile(t, PARKBLOCKER);
+    }
+
+    /**
+     * Disables the current thread for thread scheduling purposes unless the
+     * permit is available.
+     *
+     * <p>If the permit is available then it is consumed and the call
+     * returns immediately; otherwise the current thread becomes disabled
+     * for thread scheduling purposes and lies dormant until one of three
+     * things happens:
+     *
+     * <ul>
+     *
+     * <li>Some other thread invokes {@link #unpark unpark} with the
+     * current thread as the target; or
+     *
+     * <li>Some other thread {@linkplain Thread#interrupt interrupts}
+     * the current thread; or
+     *
+     * <li>The call spuriously (that is, for no reason) returns.
+     * </ul>
+     *
+     * <p>This method does <em>not</em> report which of these caused the
+     * method to return. Callers should re-check the conditions which caused
+     * the thread to park in the first place. Callers may also determine,
+     * for example, the interrupt status of the thread upon return.
+     */
+    public static void park() {
+        U.park(false, 0L);
+    }
+
+    /**
+     * Disables the current thread for thread scheduling purposes, for up to
+     * the specified waiting time, unless the permit is available.
+     *
+     * <p>If the permit is available then it is consumed and the call
+     * returns immediately; otherwise the current thread becomes disabled
+     * for thread scheduling purposes and lies dormant until one of four
+     * things happens:
+     *
+     * <ul>
+     * <li>Some other thread invokes {@link #unpark unpark} with the
+     * current thread as the target; or
+     *
+     * <li>Some other thread {@linkplain Thread#interrupt interrupts}
+     * the current thread; or
+     *
+     * <li>The specified waiting time elapses; or
+     *
+     * <li>The call spuriously (that is, for no reason) returns.
+     * </ul>
+     *
+     * <p>This method does <em>not</em> report which of these caused the
+     * method to return. Callers should re-check the conditions which caused
+     * the thread to park in the first place. Callers may also determine,
+     * for example, the interrupt status of the thread, or the elapsed time
+     * upon return.
+     *
+     * @param nanos the maximum number of nanoseconds to wait
+     */
+    public static void parkNanos(long nanos) {
+        if (nanos > 0)
+            U.park(false, nanos);
+    }
+
+    /**
+     * Disables the current thread for thread scheduling purposes, until
+     * the specified deadline, unless the permit is available.
+     *
+     * <p>If the permit is available then it is consumed and the call
+     * returns immediately; otherwise the current thread becomes disabled
+     * for thread scheduling purposes and lies dormant until one of four
+     * things happens:
+     *
+     * <ul>
+     * <li>Some other thread invokes {@link #unpark unpark} with the
+     * current thread as the target; or
+     *
+     * <li>Some other thread {@linkplain Thread#interrupt interrupts}
+     * the current thread; or
+     *
+     * <li>The specified deadline passes; or
+     *
+     * <li>The call spuriously (that is, for no reason) returns.
+     * </ul>
+     *
+     * <p>This method does <em>not</em> report which of these caused the
+     * method to return. Callers should re-check the conditions which caused
+     * the thread to park in the first place. Callers may also determine,
+     * for example, the interrupt status of the thread, or the current time
+     * upon return.
+     *
+     * @param deadline the absolute time, in milliseconds from the Epoch,
+     *        to wait until
+     */
+    public static void parkUntil(long deadline) {
+        U.park(true, deadline);
+    }
+
+    /**
+     * Returns the pseudo-randomly initialized or updated secondary seed.
+     * Copied from ThreadLocalRandom due to package access restrictions.
+     */
+    static final int nextSecondarySeed() {
+        int r;
+        Thread t = Thread.currentThread();
+        if ((r = U.getInt(t, SECONDARY)) != 0) {
+            r ^= r << 13;   // xorshift
+            r ^= r >>> 17;
+            r ^= r << 5;
+        }
+        else if ((r = java.util.concurrent.ThreadLocalRandom.current().nextInt()) == 0)
+            r = 1; // avoid zero
+        U.putInt(t, SECONDARY, r);
+        return r;
+    }
+
+    /**
+     * Returns the thread id for the given thread.  We must access
+     * this directly rather than via method Thread.getId() because
+     * getId() is not final, and has been known to be overridden in
+     * ways that do not preserve unique mappings.
+     */
+    static final long getThreadId(Thread thread) {
+        return U.getLongVolatile(thread, TID);
+    }
+
+    // Hotspot implementation via intrinsics API
+    private static final Unsafe U = Unsafe.getUnsafe();
+    private static final long PARKBLOCKER = U.objectFieldOffset
+            (Thread.class, "parkBlocker");
+    private static final long SECONDARY = U.objectFieldOffset
+            (Thread.class, "threadLocalRandomSecondarySeed");
+    private static final long TID = U.objectFieldOffset
+            (Thread.class, "tid");
+
+}

src/java.base/share/classes/java/util/concurrent/locks/ReadWriteLock.java

@@ -0,0 +1,132 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent.locks;
+
+/**
+ * A {@code ReadWriteLock} maintains a pair of associated {@link
+ * Lock locks}, one for read-only operations and one for writing.
+ * The {@linkplain #readLock read lock} may be held simultaneously
+ * by multiple reader threads, so long as there are no writers.
+ * The {@linkplain #writeLock write lock} is exclusive.
+ *
+ * <p>All {@code ReadWriteLock} implementations must guarantee that
+ * the memory synchronization effects of {@code writeLock} operations
+ * (as specified in the {@link Lock} interface) also hold with respect
+ * to the associated {@code readLock}. That is, a thread successfully
+ * acquiring the read lock will see all updates made upon previous
+ * release of the write lock.
+ *
+ * <p>A read-write lock allows for a greater level of concurrency in
+ * accessing shared data than that permitted by a mutual exclusion lock.
+ * It exploits the fact that while only a single thread at a time (a
+ * <em>writer</em> thread) can modify the shared data, in many cases any
+ * number of threads can concurrently read the data (hence <em>reader</em>
+ * threads).
+ * In theory, the increase in concurrency permitted by the use of a read-write
+ * lock will lead to performance improvements over the use of a mutual
+ * exclusion lock. In practice this increase in concurrency will only be fully
+ * realized on a multi-processor, and then only if the access patterns for
+ * the shared data are suitable.
+ *
+ * <p>Whether or not a read-write lock will improve performance over the use
+ * of a mutual exclusion lock depends on the frequency that the data is
+ * read compared to being modified, the duration of the read and write
+ * operations, and the contention for the data - that is, the number of
+ * threads that will try to read or write the data at the same time.
+ * For example, a collection that is initially populated with data and
+ * thereafter infrequently modified, while being frequently searched
+ * (such as a directory of some kind) is an ideal candidate for the use of
+ * a read-write lock. However, if updates become frequent then the data
+ * spends most of its time being exclusively locked and there is little, if any
+ * increase in concurrency. Further, if the read operations are too short
+ * the overhead of the read-write lock implementation (which is inherently
+ * more complex than a mutual exclusion lock) can dominate the execution
+ * cost, particularly as many read-write lock implementations still serialize
+ * all threads through a small section of code. Ultimately, only profiling
+ * and measurement will establish whether the use of a read-write lock is
+ * suitable for your application.
+ *
+ * <p>Although the basic operation of a read-write lock is straight-forward,
+ * there are many policy decisions that an implementation must make, which
+ * may affect the effectiveness of the read-write lock in a given application.
+ * Examples of these policies include:
+ * <ul>
+ * <li>Determining whether to grant the read lock or the write lock, when
+ * both readers and writers are waiting, at the time that a writer releases
+ * the write lock. Writer preference is common, as writes are expected to be
+ * short and infrequent. Reader preference is less common as it can lead to
+ * lengthy delays for a write if the readers are frequent and long-lived as
+ * expected. Fair, or &quot;in-order&quot; implementations are also possible.
+ *
+ * <li>Determining whether readers that request the read lock while a
+ * reader is active and a writer is waiting, are granted the read lock.
+ * Preference to the reader can delay the writer indefinitely, while
+ * preference to the writer can reduce the potential for concurrency.
+ *
+ * <li>Determining whether the locks are reentrant: can a thread with the
+ * write lock reacquire it? Can it acquire a read lock while holding the
+ * write lock? Is the read lock itself reentrant?
+ *
+ * <li>Can the write lock be downgraded to a read lock without allowing
+ * an intervening writer? Can a read lock be upgraded to a write lock,
+ * in preference to other waiting readers or writers?
+ *
+ * </ul>
+ * You should consider all of these things when evaluating the suitability
+ * of a given implementation for your application.
+ *
+ * @see ReentrantReadWriteLock
+ * @see Lock
+ * @see ReentrantLock
+ *
+ * @since 1.5
+ * @author Doug Lea
+ */
+public interface ReadWriteLock {
+    /**
+     * Returns the lock used for reading.
+     *
+     * @return the lock used for reading
+     */
+    Lock readLock();
+
+    /**
+     * Returns the lock used for writing.
+     *
+     * @return the lock used for writing
+     */
+    Lock writeLock();
+}

src/java.base/share/classes/java/util/concurrent/locks/ReentrantLock.java

@@ -0,0 +1,743 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent.locks;
+
+import java.util.Collection;
+import java.util.concurrent.TimeUnit;
+import jdk.internal.vm.annotation.ReservedStackAccess;
+
+/**
+ * A reentrant mutual exclusion {@link Lock} with the same basic
+ * behavior and semantics as the implicit monitor lock accessed using
+ * {@code synchronized} methods and statements, but with extended
+ * capabilities.
+ *
+ * <p>A {@code ReentrantLock} is <em>owned</em> by the thread last
+ * successfully locking, but not yet unlocking it. A thread invoking
+ * {@code lock} will return, successfully acquiring the lock, when
+ * the lock is not owned by another thread. The method will return
+ * immediately if the current thread already owns the lock. This can
+ * be checked using methods {@link #isHeldByCurrentThread}, and {@link
+ * #getHoldCount}.
+ *
+ * <p>The constructor for this class accepts an optional
+ * <em>fairness</em> parameter.  When set {@code true}, under
+ * contention, locks favor granting access to the longest-waiting
+ * thread.  Otherwise this lock does not guarantee any particular
+ * access order.  Programs using fair locks accessed by many threads
+ * may display lower overall throughput (i.e., are slower; often much
+ * slower) than those using the default setting, but have smaller
+ * variances in times to obtain locks and guarantee lack of
+ * starvation. Note however, that fairness of locks does not guarantee
+ * fairness of thread scheduling. Thus, one of many threads using a
+ * fair lock may obtain it multiple times in succession while other
+ * active threads are not progressing and not currently holding the
+ * lock.
+ * Also note that the untimed {@link #tryLock()} method does not
+ * honor the fairness setting. It will succeed if the lock
+ * is available even if other threads are waiting.
+ *
+ * <p>It is recommended practice to <em>always</em> immediately
+ * follow a call to {@code lock} with a {@code try} block, most
+ * typically in a before/after construction such as:
+ *
+ * <pre> {@code
+ * class X {
+ *   private final ReentrantLock lock = new ReentrantLock();
+ *   // ...
+ *
+ *   public void m() {
+ *     lock.lock();  // block until condition holds
+ *     try {
+ *       // ... method body
+ *     } finally {
+ *       lock.unlock()
+ *     }
+ *   }
+ * }}</pre>
+ *
+ * <p>In addition to implementing the {@link Lock} interface, this
+ * class defines a number of {@code public} and {@code protected}
+ * methods for inspecting the state of the lock.  Some of these
+ * methods are only useful for instrumentation and monitoring.
+ *
+ * <p>Serialization of this class behaves in the same way as built-in
+ * locks: a deserialized lock is in the unlocked state, regardless of
+ * its state when serialized.
+ *
+ * <p>This lock supports a maximum of 2147483647 recursive locks by
+ * the same thread. Attempts to exceed this limit result in
+ * {@link Error} throws from locking methods.
+ *
+ * @since 1.5
+ * @author Doug Lea
+ */
+public class ReentrantLock implements Lock, java.io.Serializable {
+    private static final long serialVersionUID = 7373984872572414699L;
+    /** Synchronizer providing all implementation mechanics */
+    private final Sync sync;
+
+    /**
+     * Base of synchronization control for this lock. Subclassed
+     * into fair and nonfair versions below. Uses AQS state to
+     * represent the number of holds on the lock.
+     */
+    abstract static class Sync extends AbstractQueuedSynchronizer {
+        private static final long serialVersionUID = -5179523762034025860L;
+
+        /**
+         * Performs non-fair tryLock.  tryAcquire is implemented in
+         * subclasses, but both need nonfair try for trylock method.
+         */
+        @ReservedStackAccess
+        final boolean nonfairTryAcquire(int acquires) {
+            final Thread current = Thread.currentThread();
+            int c = getState();
+            if (c == 0) {
+                if (compareAndSetState(0, acquires)) {
+                    setExclusiveOwnerThread(current);
+                    return true;
+                }
+            }
+            else if (current == getExclusiveOwnerThread()) {
+                int nextc = c + acquires;
+                if (nextc < 0) // overflow
+                    throw new Error("Maximum lock count exceeded");
+                setState(nextc);
+                return true;
+            }
+            return false;
+        }
+
+        @ReservedStackAccess
+        protected final boolean tryRelease(int releases) {
+            int c = getState() - releases;
+            if (Thread.currentThread() != getExclusiveOwnerThread())
+                throw new IllegalMonitorStateException();
+            boolean free = false;
+            if (c == 0) {
+                free = true;
+                setExclusiveOwnerThread(null);
+            }
+            setState(c);
+            return free;
+        }
+
+        protected final boolean isHeldExclusively() {
+            // While we must in general read state before owner,
+            // we don't need to do so to check if current thread is owner
+            return getExclusiveOwnerThread() == Thread.currentThread();
+        }
+
+        final ConditionObject newCondition() {
+            return new ConditionObject();
+        }
+
+        // Methods relayed from outer class
+
+        final Thread getOwner() {
+            return getState() == 0 ? null : getExclusiveOwnerThread();
+        }
+
+        final int getHoldCount() {
+            return isHeldExclusively() ? getState() : 0;
+        }
+
+        final boolean isLocked() {
+            return getState() != 0;
+        }
+
+        /**
+         * Reconstitutes the instance from a stream (that is, deserializes it).
+         */
+        private void readObject(java.io.ObjectInputStream s)
+            throws java.io.IOException, ClassNotFoundException {
+            s.defaultReadObject();
+            setState(0); // reset to unlocked state
+        }
+    }
+
+    /**
+     * Sync object for non-fair locks
+     */
+    static final class NonfairSync extends Sync {
+        private static final long serialVersionUID = 7316153563782823691L;
+        protected final boolean tryAcquire(int acquires) {
+            return nonfairTryAcquire(acquires);
+        }
+    }
+
+    /**
+     * Sync object for fair locks
+     */
+    static final class FairSync extends Sync {
+        private static final long serialVersionUID = -3000897897090466540L;
+        /**
+         * Fair version of tryAcquire.  Don't grant access unless
+         * recursive call or no waiters or is first.
+         */
+        @ReservedStackAccess
+        protected final boolean tryAcquire(int acquires) {
+            final Thread current = Thread.currentThread();
+            int c = getState();
+            if (c == 0) {
+                if (!hasQueuedPredecessors() &&
+                    compareAndSetState(0, acquires)) {
+                    setExclusiveOwnerThread(current);
+                    return true;
+                }
+            }
+            else if (current == getExclusiveOwnerThread()) {
+                int nextc = c + acquires;
+                if (nextc < 0)
+                    throw new Error("Maximum lock count exceeded");
+                setState(nextc);
+                return true;
+            }
+            return false;
+        }
+    }
+
+    /**
+     * Creates an instance of {@code ReentrantLock}.
+     * This is equivalent to using {@code ReentrantLock(false)}.
+     */
+    public ReentrantLock() {
+        sync = new NonfairSync();
+    }
+
+    /**
+     * Creates an instance of {@code ReentrantLock} with the
+     * given fairness policy.
+     *
+     * @param fair {@code true} if this lock should use a fair ordering policy
+     */
+    public ReentrantLock(boolean fair) {
+        sync = fair ? new FairSync() : new NonfairSync();
+    }
+
+    /**
+     * Acquires the lock.
+     *
+     * <p>Acquires the lock if it is not held by another thread and returns
+     * immediately, setting the lock hold count to one.
+     *
+     * <p>If the current thread already holds the lock then the hold
+     * count is incremented by one and the method returns immediately.
+     *
+     * <p>If the lock is held by another thread then the
+     * current thread becomes disabled for thread scheduling
+     * purposes and lies dormant until the lock has been acquired,
+     * at which time the lock hold count is set to one.
+     */
+    public void lock() {
+        sync.acquire(1);
+    }
+
+    /**
+     * Acquires the lock unless the current thread is
+     * {@linkplain Thread#interrupt interrupted}.
+     *
+     * <p>Acquires the lock if it is not held by another thread and returns
+     * immediately, setting the lock hold count to one.
+     *
+     * <p>If the current thread already holds this lock then the hold count
+     * is incremented by one and the method returns immediately.
+     *
+     * <p>If the lock is held by another thread then the
+     * current thread becomes disabled for thread scheduling
+     * purposes and lies dormant until one of two things happens:
+     *
+     * <ul>
+     *
+     * <li>The lock is acquired by the current thread; or
+     *
+     * <li>Some other thread {@linkplain Thread#interrupt interrupts} the
+     * current thread.
+     *
+     * </ul>
+     *
+     * <p>If the lock is acquired by the current thread then the lock hold
+     * count is set to one.
+     *
+     * <p>If the current thread:
+     *
+     * <ul>
+     *
+     * <li>has its interrupted status set on entry to this method; or
+     *
+     * <li>is {@linkplain Thread#interrupt interrupted} while acquiring
+     * the lock,
+     *
+     * </ul>
+     *
+     * then {@link InterruptedException} is thrown and the current thread's
+     * interrupted status is cleared.
+     *
+     * <p>In this implementation, as this method is an explicit
+     * interruption point, preference is given to responding to the
+     * interrupt over normal or reentrant acquisition of the lock.
+     *
+     * @throws InterruptedException if the current thread is interrupted
+     */
+    public void lockInterruptibly() throws InterruptedException {
+        sync.acquireInterruptibly(1);
+    }
+
+    /**
+     * Acquires the lock only if it is not held by another thread at the time
+     * of invocation.
+     *
+     * <p>Acquires the lock if it is not held by another thread and
+     * returns immediately with the value {@code true}, setting the
+     * lock hold count to one. Even when this lock has been set to use a
+     * fair ordering policy, a call to {@code tryLock()} <em>will</em>
+     * immediately acquire the lock if it is available, whether or not
+     * other threads are currently waiting for the lock.
+     * This &quot;barging&quot; behavior can be useful in certain
+     * circumstances, even though it breaks fairness. If you want to honor
+     * the fairness setting for this lock, then use
+     * {@link #tryLock(long, TimeUnit) tryLock(0, TimeUnit.SECONDS)}
+     * which is almost equivalent (it also detects interruption).
+     *
+     * <p>If the current thread already holds this lock then the hold
+     * count is incremented by one and the method returns {@code true}.
+     *
+     * <p>If the lock is held by another thread then this method will return
+     * immediately with the value {@code false}.
+     *
+     * @return {@code true} if the lock was free and was acquired by the
+     *         current thread, or the lock was already held by the current
+     *         thread; and {@code false} otherwise
+     */
+    public boolean tryLock() {
+        return sync.nonfairTryAcquire(1);
+    }
+
+    /**
+     * Acquires the lock if it is not held by another thread within the given
+     * waiting time and the current thread has not been
+     * {@linkplain Thread#interrupt interrupted}.
+     *
+     * <p>Acquires the lock if it is not held by another thread and returns
+     * immediately with the value {@code true}, setting the lock hold count
+     * to one. If this lock has been set to use a fair ordering policy then
+     * an available lock <em>will not</em> be acquired if any other threads
+     * are waiting for the lock. This is in contrast to the {@link #tryLock()}
+     * method. If you want a timed {@code tryLock} that does permit barging on
+     * a fair lock then combine the timed and un-timed forms together:
+     *
+     * <pre> {@code
+     * if (lock.tryLock() ||
+     *     lock.tryLock(timeout, unit)) {
+     *   ...
+     * }}</pre>
+     *
+     * <p>If the current thread
+     * already holds this lock then the hold count is incremented by one and
+     * the method returns {@code true}.
+     *
+     * <p>If the lock is held by another thread then the
+     * current thread becomes disabled for thread scheduling
+     * purposes and lies dormant until one of three things happens:
+     *
+     * <ul>
+     *
+     * <li>The lock is acquired by the current thread; or
+     *
+     * <li>Some other thread {@linkplain Thread#interrupt interrupts}
+     * the current thread; or
+     *
+     * <li>The specified waiting time elapses
+     *
+     * </ul>
+     *
+     * <p>If the lock is acquired then the value {@code true} is returned and
+     * the lock hold count is set to one.
+     *
+     * <p>If the current thread:
+     *
+     * <ul>
+     *
+     * <li>has its interrupted status set on entry to this method; or
+     *
+     * <li>is {@linkplain Thread#interrupt interrupted} while
+     * acquiring the lock,
+     *
+     * </ul>
+     * then {@link InterruptedException} is thrown and the current thread's
+     * interrupted status is cleared.
+     *
+     * <p>If the specified waiting time elapses then the value {@code false}
+     * is returned.  If the time is less than or equal to zero, the method
+     * will not wait at all.
+     *
+     * <p>In this implementation, as this method is an explicit
+     * interruption point, preference is given to responding to the
+     * interrupt over normal or reentrant acquisition of the lock, and
+     * over reporting the elapse of the waiting time.
+     *
+     * @param timeout the time to wait for the lock
+     * @param unit the time unit of the timeout argument
+     * @return {@code true} if the lock was free and was acquired by the
+     *         current thread, or the lock was already held by the current
+     *         thread; and {@code false} if the waiting time elapsed before
+     *         the lock could be acquired
+     * @throws InterruptedException if the current thread is interrupted
+     * @throws NullPointerException if the time unit is null
+     */
+    public boolean tryLock(long timeout, TimeUnit unit)
+            throws InterruptedException {
+        return sync.tryAcquireNanos(1, unit.toNanos(timeout));
+    }
+
+    /**
+     * Attempts to release this lock.
+     *
+     * <p>If the current thread is the holder of this lock then the hold
+     * count is decremented.  If the hold count is now zero then the lock
+     * is released.  If the current thread is not the holder of this
+     * lock then {@link IllegalMonitorStateException} is thrown.
+     *
+     * @throws IllegalMonitorStateException if the current thread does not
+     *         hold this lock
+     */
+    public void unlock() {
+        sync.release(1);
+    }
+
+    /**
+     * Returns a {@link Condition} instance for use with this
+     * {@link Lock} instance.
+     *
+     * <p>The returned {@link Condition} instance supports the same
+     * usages as do the {@link Object} monitor methods ({@link
+     * Object#wait() wait}, {@link Object#notify notify}, and {@link
+     * Object#notifyAll notifyAll}) when used with the built-in
+     * monitor lock.
+     *
+     * <ul>
+     *
+     * <li>If this lock is not held when any of the {@link Condition}
+     * {@linkplain Condition#await() waiting} or {@linkplain
+     * Condition#signal signalling} methods are called, then an {@link
+     * IllegalMonitorStateException} is thrown.
+     *
+     * <li>When the condition {@linkplain Condition#await() waiting}
+     * methods are called the lock is released and, before they
+     * return, the lock is reacquired and the lock hold count restored
+     * to what it was when the method was called.
+     *
+     * <li>If a thread is {@linkplain Thread#interrupt interrupted}
+     * while waiting then the wait will terminate, an {@link
+     * InterruptedException} will be thrown, and the thread's
+     * interrupted status will be cleared.
+     *
+     * <li>Waiting threads are signalled in FIFO order.
+     *
+     * <li>The ordering of lock reacquisition for threads returning
+     * from waiting methods is the same as for threads initially
+     * acquiring the lock, which is in the default case not specified,
+     * but for <em>fair</em> locks favors those threads that have been
+     * waiting the longest.
+     *
+     * </ul>
+     *
+     * @return the Condition object
+     */
+    public Condition newCondition() {
+        return sync.newCondition();
+    }
+
+    /**
+     * Queries the number of holds on this lock by the current thread.
+     *
+     * <p>A thread has a hold on a lock for each lock action that is not
+     * matched by an unlock action.
+     *
+     * <p>The hold count information is typically only used for testing and
+     * debugging purposes. For example, if a certain section of code should
+     * not be entered with the lock already held then we can assert that
+     * fact:
+     *
+     * <pre> {@code
+     * class X {
+     *   ReentrantLock lock = new ReentrantLock();
+     *   // ...
+     *   public void m() {
+     *     assert lock.getHoldCount() == 0;
+     *     lock.lock();
+     *     try {
+     *       // ... method body
+     *     } finally {
+     *       lock.unlock();
+     *     }
+     *   }
+     * }}</pre>
+     *
+     * @return the number of holds on this lock by the current thread,
+     *         or zero if this lock is not held by the current thread
+     */
+    public int getHoldCount() {
+        return sync.getHoldCount();
+    }
+
+    /**
+     * Queries if this lock is held by the current thread.
+     *
+     * <p>Analogous to the {@link Thread#holdsLock(Object)} method for
+     * built-in monitor locks, this method is typically used for
+     * debugging and testing. For example, a method that should only be
+     * called while a lock is held can assert that this is the case:
+     *
+     * <pre> {@code
+     * class X {
+     *   ReentrantLock lock = new ReentrantLock();
+     *   // ...
+     *
+     *   public void m() {
+     *       assert lock.isHeldByCurrentThread();
+     *       // ... method body
+     *   }
+     * }}</pre>
+     *
+     * <p>It can also be used to ensure that a reentrant lock is used
+     * in a non-reentrant manner, for example:
+     *
+     * <pre> {@code
+     * class X {
+     *   ReentrantLock lock = new ReentrantLock();
+     *   // ...
+     *
+     *   public void m() {
+     *       assert !lock.isHeldByCurrentThread();
+     *       lock.lock();
+     *       try {
+     *           // ... method body
+     *       } finally {
+     *           lock.unlock();
+     *       }
+     *   }
+     * }}</pre>
+     *
+     * @return {@code true} if current thread holds this lock and
+     *         {@code false} otherwise
+     */
+    public boolean isHeldByCurrentThread() {
+        return sync.isHeldExclusively();
+    }
+
+    /**
+     * Queries if this lock is held by any thread. This method is
+     * designed for use in monitoring of the system state,
+     * not for synchronization control.
+     *
+     * @return {@code true} if any thread holds this lock and
+     *         {@code false} otherwise
+     */
+    public boolean isLocked() {
+        return sync.isLocked();
+    }
+
+    /**
+     * Returns {@code true} if this lock has fairness set true.
+     *
+     * @return {@code true} if this lock has fairness set true
+     */
+    public final boolean isFair() {
+        return sync instanceof FairSync;
+    }
+
+    /**
+     * Returns the thread that currently owns this lock, or
+     * {@code null} if not owned. When this method is called by a
+     * thread that is not the owner, the return value reflects a
+     * best-effort approximation of current lock status. For example,
+     * the owner may be momentarily {@code null} even if there are
+     * threads trying to acquire the lock but have not yet done so.
+     * This method is designed to facilitate construction of
+     * subclasses that provide more extensive lock monitoring
+     * facilities.
+     *
+     * @return the owner, or {@code null} if not owned
+     */
+    protected Thread getOwner() {
+        return sync.getOwner();
+    }
+
+    /**
+     * Queries whether any threads are waiting to acquire this lock. Note that
+     * because cancellations may occur at any time, a {@code true}
+     * return does not guarantee that any other thread will ever
+     * acquire this lock.  This method is designed primarily for use in
+     * monitoring of the system state.
+     *
+     * @return {@code true} if there may be other threads waiting to
+     *         acquire the lock
+     */
+    public final boolean hasQueuedThreads() {
+        return sync.hasQueuedThreads();
+    }
+
+    /**
+     * Queries whether the given thread is waiting to acquire this
+     * lock. Note that because cancellations may occur at any time, a
+     * {@code true} return does not guarantee that this thread
+     * will ever acquire this lock.  This method is designed primarily for use
+     * in monitoring of the system state.
+     *
+     * @param thread the thread
+     * @return {@code true} if the given thread is queued waiting for this lock
+     * @throws NullPointerException if the thread is null
+     */
+    public final boolean hasQueuedThread(Thread thread) {
+        return sync.isQueued(thread);
+    }
+
+    /**
+     * Returns an estimate of the number of threads waiting to acquire
+     * this lock.  The value is only an estimate because the number of
+     * threads may change dynamically while this method traverses
+     * internal data structures.  This method is designed for use in
+     * monitoring system state, not for synchronization control.
+     *
+     * @return the estimated number of threads waiting for this lock
+     */
+    public final int getQueueLength() {
+        return sync.getQueueLength();
+    }
+
+    /**
+     * Returns a collection containing threads that may be waiting to
+     * acquire this lock.  Because the actual set of threads may change
+     * dynamically while constructing this result, the returned
+     * collection is only a best-effort estimate.  The elements of the
+     * returned collection are in no particular order.  This method is
+     * designed to facilitate construction of subclasses that provide
+     * more extensive monitoring facilities.
+     *
+     * @return the collection of threads
+     */
+    protected Collection<Thread> getQueuedThreads() {
+        return sync.getQueuedThreads();
+    }
+
+    /**
+     * Queries whether any threads are waiting on the given condition
+     * associated with this lock. Note that because timeouts and
+     * interrupts may occur at any time, a {@code true} return does
+     * not guarantee that a future {@code signal} will awaken any
+     * threads.  This method is designed primarily for use in
+     * monitoring of the system state.
+     *
+     * @param condition the condition
+     * @return {@code true} if there are any waiting threads
+     * @throws IllegalMonitorStateException if this lock is not held
+     * @throws IllegalArgumentException if the given condition is
+     *         not associated with this lock
+     * @throws NullPointerException if the condition is null
+     */
+    public boolean hasWaiters(Condition condition) {
+        if (condition == null)
+            throw new NullPointerException();
+        if (!(condition instanceof AbstractQueuedSynchronizer.ConditionObject))
+            throw new IllegalArgumentException("not owner");
+        return sync.hasWaiters((AbstractQueuedSynchronizer.ConditionObject)condition);
+    }
+
+    /**
+     * Returns an estimate of the number of threads waiting on the
+     * given condition associated with this lock. Note that because
+     * timeouts and interrupts may occur at any time, the estimate
+     * serves only as an upper bound on the actual number of waiters.
+     * This method is designed for use in monitoring of the system
+     * state, not for synchronization control.
+     *
+     * @param condition the condition
+     * @return the estimated number of waiting threads
+     * @throws IllegalMonitorStateException if this lock is not held
+     * @throws IllegalArgumentException if the given condition is
+     *         not associated with this lock
+     * @throws NullPointerException if the condition is null
+     */
+    public int getWaitQueueLength(Condition condition) {
+        if (condition == null)
+            throw new NullPointerException();
+        if (!(condition instanceof AbstractQueuedSynchronizer.ConditionObject))
+            throw new IllegalArgumentException("not owner");
+        return sync.getWaitQueueLength((AbstractQueuedSynchronizer.ConditionObject)condition);
+    }
+
+    /**
+     * Returns a collection containing those threads that may be
+     * waiting on the given condition associated with this lock.
+     * Because the actual set of threads may change dynamically while
+     * constructing this result, the returned collection is only a
+     * best-effort estimate. The elements of the returned collection
+     * are in no particular order.  This method is designed to
+     * facilitate construction of subclasses that provide more
+     * extensive condition monitoring facilities.
+     *
+     * @param condition the condition
+     * @return the collection of threads
+     * @throws IllegalMonitorStateException if this lock is not held
+     * @throws IllegalArgumentException if the given condition is
+     *         not associated with this lock
+     * @throws NullPointerException if the condition is null
+     */
+    protected Collection<Thread> getWaitingThreads(Condition condition) {
+        if (condition == null)
+            throw new NullPointerException();
+        if (!(condition instanceof AbstractQueuedSynchronizer.ConditionObject))
+            throw new IllegalArgumentException("not owner");
+        return sync.getWaitingThreads((AbstractQueuedSynchronizer.ConditionObject)condition);
+    }
+
+    /**
+     * Returns a string identifying this lock, as well as its lock state.
+     * The state, in brackets, includes either the String {@code "Unlocked"}
+     * or the String {@code "Locked by"} followed by the
+     * {@linkplain Thread#getName name} of the owning thread.
+     *
+     * @return a string identifying this lock, as well as its lock state
+     */
+    public String toString() {
+        Thread o = sync.getOwner();
+        return super.toString() + ((o == null) ?
+                                   "[Unlocked]" :
+                                   "[Locked by thread " + o.getName() + "]");
+    }
+}

src/java.base/share/classes/java/util/concurrent/locks/package-info.java

@@ -0,0 +1,79 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+/**
+ * Interfaces and classes providing a framework for locking and waiting
+ * for conditions that is distinct from built-in synchronization and
+ * monitors.  The framework permits much greater flexibility in the use of
+ * locks and conditions, at the expense of more awkward syntax.
+ *
+ * <p>The {@link java.util.concurrent.locks.Lock} interface supports
+ * locking disciplines that differ in semantics (reentrant, fair, etc),
+ * and that can be used in non-block-structured contexts including
+ * hand-over-hand and lock reordering algorithms.  The main implementation
+ * is {@link java.util.concurrent.locks.ReentrantLock}.
+ *
+ * <p>The {@link java.util.concurrent.locks.ReadWriteLock} interface
+ * similarly defines locks that may be shared among readers but are
+ * exclusive to writers.  Only a single implementation, {@link
+ * java.util.concurrent.locks.ReentrantReadWriteLock}, is provided, since
+ * it covers most standard usage contexts.  But programmers may create
+ * their own implementations to cover nonstandard requirements.
+ *
+ * <p>The {@link java.util.concurrent.locks.Condition} interface
+ * describes condition variables that may be associated with Locks.
+ * These are similar in usage to the implicit monitors accessed using
+ * {@code Object.wait}, but offer extended capabilities.
+ * In particular, multiple {@code Condition} objects may be associated
+ * with a single {@code Lock}.  To avoid compatibility issues, the
+ * names of {@code Condition} methods are different from the
+ * corresponding {@code Object} versions.
+ *
+ * <p>The {@link java.util.concurrent.locks.AbstractQueuedSynchronizer}
+ * class serves as a useful superclass for defining locks and other
+ * synchronizers that rely on queuing blocked threads.  The {@link
+ * java.util.concurrent.locks.AbstractQueuedLongSynchronizer} class
+ * provides the same functionality but extends support to 64 bits of
+ * synchronization state.  Both extend class {@link
+ * java.util.concurrent.locks.AbstractOwnableSynchronizer}, a simple
+ * class that helps record the thread currently holding exclusive
+ * synchronization.  The {@link java.util.concurrent.locks.LockSupport}
+ * class provides lower-level blocking and unblocking support that is
+ * useful for those developers implementing their own customized lock
+ * classes.
+ *
+ * @since 1.5
+ */
+package java.util.concurrent.locks;

src/java.base/share/classes/java/util/concurrent/package-info.java

@@ -0,0 +1,307 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+/**
+ * Utility classes commonly useful in concurrent programming.  This
+ * package includes a few small standardized extensible frameworks, as
+ * well as some classes that provide useful functionality and are
+ * otherwise tedious or difficult to implement.  Here are brief
+ * descriptions of the main components.  See also the
+ * {@link java.util.concurrent.locks} and
+ * {@link java.util.concurrent.atomic} packages.
+ *
+ * <h2>Executors</h2>
+ *
+ * <b>Interfaces.</b>
+ *
+ * {@link java.util.concurrent.Executor} is a simple standardized
+ * interface for defining custom thread-like subsystems, including
+ * thread pools, asynchronous I/O, and lightweight task frameworks.
+ * Depending on which concrete Executor class is being used, tasks may
+ * execute in a newly created thread, an existing task-execution thread,
+ * or the thread calling {@link java.util.concurrent.Executor#execute
+ * execute}, and may execute sequentially or concurrently.
+ *
+ * {@link java.util.concurrent.ExecutorService} provides a more
+ * complete asynchronous task execution framework.  An
+ * ExecutorService manages queuing and scheduling of tasks,
+ * and allows controlled shutdown.
+ *
+ * The {@link java.util.concurrent.ScheduledExecutorService}
+ * subinterface and associated interfaces add support for
+ * delayed and periodic task execution.  ExecutorServices
+ * provide methods arranging asynchronous execution of any
+ * function expressed as {@link java.util.concurrent.Callable},
+ * the result-bearing analog of {@link java.lang.Runnable}.
+ *
+ * A {@link java.util.concurrent.Future} returns the results of
+ * a function, allows determination of whether execution has
+ * completed, and provides a means to cancel execution.
+ *
+ * A {@link java.util.concurrent.RunnableFuture} is a {@code Future}
+ * that possesses a {@code run} method that upon execution,
+ * sets its results.
+ *
+ * <p>
+ *
+ * <b>Implementations.</b>
+ *
+ * Classes {@link java.util.concurrent.ThreadPoolExecutor} and
+ * {@link java.util.concurrent.ScheduledThreadPoolExecutor}
+ * provide tunable, flexible thread pools.
+ *
+ * The {@link java.util.concurrent.Executors} class provides
+ * factory methods for the most common kinds and configurations
+ * of Executors, as well as a few utility methods for using
+ * them.  Other utilities based on {@code Executors} include the
+ * concrete class {@link java.util.concurrent.FutureTask}
+ * providing a common extensible implementation of Futures, and
+ * {@link java.util.concurrent.ExecutorCompletionService}, that
+ * assists in coordinating the processing of groups of
+ * asynchronous tasks.
+ *
+ * <p>Class {@link java.util.concurrent.ForkJoinPool} provides an
+ * Executor primarily designed for processing instances of {@link
+ * java.util.concurrent.ForkJoinTask} and its subclasses.  These
+ * classes employ a work-stealing scheduler that attains high
+ * throughput for tasks conforming to restrictions that often hold in
+ * computation-intensive parallel processing.
+ *
+ * <h2>Queues</h2>
+ *
+ * The {@link java.util.concurrent.ConcurrentLinkedQueue} class
+ * supplies an efficient scalable thread-safe non-blocking FIFO queue.
+ * The {@link java.util.concurrent.ConcurrentLinkedDeque} class is
+ * similar, but additionally supports the {@link java.util.Deque}
+ * interface.
+ *
+ * <p>Five implementations in {@code java.util.concurrent} support
+ * the extended {@link java.util.concurrent.BlockingQueue}
+ * interface, that defines blocking versions of put and take:
+ * {@link java.util.concurrent.LinkedBlockingQueue},
+ * {@link java.util.concurrent.ArrayBlockingQueue},
+ * {@link java.util.concurrent.SynchronousQueue},
+ * {@link java.util.concurrent.PriorityBlockingQueue}, and
+ * {@link java.util.concurrent.DelayQueue}.
+ * The different classes cover the most common usage contexts
+ * for producer-consumer, messaging, parallel tasking, and
+ * related concurrent designs.
+ *
+ * <p>Extended interface {@link java.util.concurrent.TransferQueue},
+ * and implementation {@link java.util.concurrent.LinkedTransferQueue}
+ * introduce a synchronous {@code transfer} method (along with related
+ * features) in which a producer may optionally block awaiting its
+ * consumer.
+ *
+ * <p>The {@link java.util.concurrent.BlockingDeque} interface
+ * extends {@code BlockingQueue} to support both FIFO and LIFO
+ * (stack-based) operations.
+ * Class {@link java.util.concurrent.LinkedBlockingDeque}
+ * provides an implementation.
+ *
+ * <h2>Timing</h2>
+ *
+ * The {@link java.util.concurrent.TimeUnit} class provides
+ * multiple granularities (including nanoseconds) for
+ * specifying and controlling time-out based operations.  Most
+ * classes in the package contain operations based on time-outs
+ * in addition to indefinite waits.  In all cases that
+ * time-outs are used, the time-out specifies the minimum time
+ * that the method should wait before indicating that it
+ * timed-out.  Implementations make a &quot;best effort&quot;
+ * to detect time-outs as soon as possible after they occur.
+ * However, an indefinite amount of time may elapse between a
+ * time-out being detected and a thread actually executing
+ * again after that time-out.  All methods that accept timeout
+ * parameters treat values less than or equal to zero to mean
+ * not to wait at all.  To wait "forever", you can use a value
+ * of {@code Long.MAX_VALUE}.
+ *
+ * <h2>Synchronizers</h2>
+ *
+ * Five classes aid common special-purpose synchronization idioms.
+ * <ul>
+ *
+ * <li>{@link java.util.concurrent.Semaphore} is a classic concurrency tool.
+ *
+ * <li>{@link java.util.concurrent.CountDownLatch} is a very simple yet
+ * very common utility for blocking until a given number of signals,
+ * events, or conditions hold.
+ *
+ * <li>A {@link java.util.concurrent.CyclicBarrier} is a resettable
+ * multiway synchronization point useful in some styles of parallel
+ * programming.
+ *
+ * <li>A {@link java.util.concurrent.Phaser} provides
+ * a more flexible form of barrier that may be used to control phased
+ * computation among multiple threads.
+ *
+ * <li>An {@link java.util.concurrent.Exchanger} allows two threads to
+ * exchange objects at a rendezvous point, and is useful in several
+ * pipeline designs.
+ *
+ * </ul>
+ *
+ * <h2>Concurrent Collections</h2>
+ *
+ * Besides Queues, this package supplies Collection implementations
+ * designed for use in multithreaded contexts:
+ * {@link java.util.concurrent.ConcurrentHashMap},
+ * {@link java.util.concurrent.ConcurrentSkipListMap},
+ * {@link java.util.concurrent.ConcurrentSkipListSet},
+ * {@link java.util.concurrent.CopyOnWriteArrayList}, and
+ * {@link java.util.concurrent.CopyOnWriteArraySet}.
+ * When many threads are expected to access a given collection, a
+ * {@code ConcurrentHashMap} is normally preferable to a synchronized
+ * {@code HashMap}, and a {@code ConcurrentSkipListMap} is normally
+ * preferable to a synchronized {@code TreeMap}.
+ * A {@code CopyOnWriteArrayList} is preferable to a synchronized
+ * {@code ArrayList} when the expected number of reads and traversals
+ * greatly outnumber the number of updates to a list.
+ *
+ * <p>The "Concurrent" prefix used with some classes in this package
+ * is a shorthand indicating several differences from similar
+ * "synchronized" classes.  For example {@code java.util.Hashtable} and
+ * {@code Collections.synchronizedMap(new HashMap())} are
+ * synchronized.  But {@link
+ * java.util.concurrent.ConcurrentHashMap} is "concurrent".  A
+ * concurrent collection is thread-safe, but not governed by a
+ * single exclusion lock.  In the particular case of
+ * ConcurrentHashMap, it safely permits any number of
+ * concurrent reads as well as a large number of concurrent
+ * writes.  "Synchronized" classes can be useful when you need
+ * to prevent all access to a collection via a single lock, at
+ * the expense of poorer scalability.  In other cases in which
+ * multiple threads are expected to access a common collection,
+ * "concurrent" versions are normally preferable.  And
+ * unsynchronized collections are preferable when either
+ * collections are unshared, or are accessible only when
+ * holding other locks.
+ *
+ * <p id="Weakly">Most concurrent Collection implementations
+ * (including most Queues) also differ from the usual {@code java.util}
+ * conventions in that their {@linkplain java.util.Iterator Iterators}
+ * and {@linkplain java.util.Spliterator Spliterators} provide
+ * <em>weakly consistent</em> rather than fast-fail traversal:
+ * <ul>
+ * <li>they may proceed concurrently with other operations
+ * <li>they will never throw {@link java.util.ConcurrentModificationException
+ * ConcurrentModificationException}
+ * <li>they are guaranteed to traverse elements as they existed upon
+ * construction exactly once, and may (but are not guaranteed to)
+ * reflect any modifications subsequent to construction.
+ * </ul>
+ *
+ * <h2 id="MemoryVisibility">Memory Consistency Properties</h2>
+ *
+ * <a href="https://docs.oracle.com/javase/specs/jls/se8/html/jls-17.html#jls-17.4.5">
+ * Chapter 17 of
+ * <cite>The Java&trade; Language Specification</cite></a> defines the
+ * <i>happens-before</i> relation on memory operations such as reads and
+ * writes of shared variables.  The results of a write by one thread are
+ * guaranteed to be visible to a read by another thread only if the write
+ * operation <i>happens-before</i> the read operation.  The
+ * {@code synchronized} and {@code volatile} constructs, as well as the
+ * {@code Thread.start()} and {@code Thread.join()} methods, can form
+ * <i>happens-before</i> relationships.  In particular:
+ *
+ * <ul>
+ *   <li>Each action in a thread <i>happens-before</i> every action in that
+ *   thread that comes later in the program's order.
+ *
+ *   <li>An unlock ({@code synchronized} block or method exit) of a
+ *   monitor <i>happens-before</i> every subsequent lock ({@code synchronized}
+ *   block or method entry) of that same monitor.  And because
+ *   the <i>happens-before</i> relation is transitive, all actions
+ *   of a thread prior to unlocking <i>happen-before</i> all actions
+ *   subsequent to any thread locking that monitor.
+ *
+ *   <li>A write to a {@code volatile} field <i>happens-before</i> every
+ *   subsequent read of that same field.  Writes and reads of
+ *   {@code volatile} fields have similar memory consistency effects
+ *   as entering and exiting monitors, but do <em>not</em> entail
+ *   mutual exclusion locking.
+ *
+ *   <li>A call to {@code start} on a thread <i>happens-before</i> any
+ *   action in the started thread.
+ *
+ *   <li>All actions in a thread <i>happen-before</i> any other thread
+ *   successfully returns from a {@code join} on that thread.
+ *
+ * </ul>
+ *
+ * The methods of all classes in {@code java.util.concurrent} and its
+ * subpackages extend these guarantees to higher-level
+ * synchronization.  In particular:
+ *
+ * <ul>
+ *
+ *   <li>Actions in a thread prior to placing an object into any concurrent
+ *   collection <i>happen-before</i> actions subsequent to the access or
+ *   removal of that element from the collection in another thread.
+ *
+ *   <li>Actions in a thread prior to the submission of a {@code Runnable}
+ *   to an {@code Executor} <i>happen-before</i> its execution begins.
+ *   Similarly for {@code Callables} submitted to an {@code ExecutorService}.
+ *
+ *   <li>Actions taken by the asynchronous computation represented by a
+ *   {@code Future} <i>happen-before</i> actions subsequent to the
+ *   retrieval of the result via {@code Future.get()} in another thread.
+ *
+ *   <li>Actions prior to "releasing" synchronizer methods such as
+ *   {@code Lock.unlock}, {@code Semaphore.release}, and
+ *   {@code CountDownLatch.countDown} <i>happen-before</i> actions
+ *   subsequent to a successful "acquiring" method such as
+ *   {@code Lock.lock}, {@code Semaphore.acquire},
+ *   {@code Condition.await}, and {@code CountDownLatch.await} on the
+ *   same synchronizer object in another thread.
+ *
+ *   <li>For each pair of threads that successfully exchange objects via
+ *   an {@code Exchanger}, actions prior to the {@code exchange()}
+ *   in each thread <i>happen-before</i> those subsequent to the
+ *   corresponding {@code exchange()} in another thread.
+ *
+ *   <li>Actions prior to calling {@code CyclicBarrier.await} and
+ *   {@code Phaser.awaitAdvance} (as well as its variants)
+ *   <i>happen-before</i> actions performed by the barrier action, and
+ *   actions performed by the barrier action <i>happen-before</i> actions
+ *   subsequent to a successful return from the corresponding {@code await}
+ *   in other threads.
+ *
+ * </ul>
+ *
+ * @since 1.5
+ */
+package java.util.concurrent;