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8187443: Forest Consolidation: Move files to unified layout
Reviewed-by: darcy, ihse
This commit is contained in:
Erik Joelsson
parent
270fe13182
commit
3789983e89
56923 changed files with 3 additions and 15727 deletions
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@ -0,0 +1,486 @@
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/*
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
|
||||
*
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||||
* 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:
|
||||
*
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||||
* 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/
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||||
*/
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package java.util.concurrent.locks;
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import java.util.Date;
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import java.util.concurrent.TimeUnit;
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|
||||
/**
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||||
* {@code Condition} factors out the {@code Object} monitor
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* methods ({@link Object#wait() wait}, {@link Object#notify notify}
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* and {@link Object#notifyAll notifyAll}) into distinct objects to
|
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* 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 "wait") 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
|
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* suspends the current thread, just like {@code Object.wait}.
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*
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* <p>A {@code Condition} instance is intrinsically bound to a lock.
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||||
* To obtain a {@code Condition} instance for a particular {@link Lock}
|
||||
* instance use its {@link Lock#newCondition newCondition()} method.
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||||
*
|
||||
* <p>As an example, suppose we have a bounded buffer which supports
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* {@code put} and {@code take} methods. If a
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* {@code take} is attempted on an empty buffer, then the thread will block
|
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* until an item becomes available; if a {@code put} is attempted on a
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* full buffer, then the thread will block until a space becomes available.
|
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* We would like to keep waiting {@code put} threads and {@code take}
|
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* threads in separate wait-sets so that we can use the optimization of
|
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* only notifying a single thread at a time when items or spaces become
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||||
* available in the buffer. This can be achieved using two
|
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* {@link Condition} instances.
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* <pre>
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* class BoundedBuffer {
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* <b>final Lock lock = new ReentrantLock();</b>
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* final Condition notFull = <b>lock.newCondition(); </b>
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* final Condition notEmpty = <b>lock.newCondition(); </b>
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*
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* final Object[] items = new Object[100];
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* int putptr, takeptr, count;
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*
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* public void put(Object x) throws InterruptedException {
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* <b>lock.lock();
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* try {</b>
|
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* while (count == items.length)
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* <b>notFull.await();</b>
|
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* items[putptr] = x;
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* if (++putptr == items.length) putptr = 0;
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* ++count;
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* <b>notEmpty.signal();</b>
|
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* <b>} finally {
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* lock.unlock();
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* }</b>
|
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* }
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*
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* public Object take() throws InterruptedException {
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* <b>lock.lock();
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* try {</b>
|
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* while (count == 0)
|
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* <b>notEmpty.await();</b>
|
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* 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
|
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* that is
|
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* different from that of the {@code Object} monitor methods, such as
|
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* guaranteed ordering for notifications, or not requiring a lock to be held
|
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* when performing notifications.
|
||||
* If an implementation provides such specialized semantics then the
|
||||
* implementation must document those semantics.
|
||||
*
|
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* <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.
|
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* It is recommended that to avoid confusion you never use {@code Condition}
|
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* instances in this way, except perhaps within their own implementation.
|
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*
|
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* <p>Except where noted, passing a {@code null} value for any parameter
|
||||
* will result in a {@link NullPointerException} being thrown.
|
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*
|
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* <h3>Implementation Considerations</h3>
|
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*
|
||||
* <p>When waiting upon a {@code Condition}, a "<em>spurious
|
||||
* wakeup</em>" 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
|
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* 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
|
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* (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.
|
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*
|
||||
* <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.
|
||||
*
|
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* @since 1.5
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* @author Doug Lea
|
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*/
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public interface Condition {
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|
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/**
|
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* Causes the current thread to wait until it is signalled or
|
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* {@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 "<em>spurious wakeup</em>" 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 "<em>spurious wakeup</em>" 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 "<em>spurious wakeup</em>" 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 "<em>spurious wakeup</em>" 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();
|
||||
}
|
||||
Loading…
Add table
Add a link
Reference in a new issue