8187443: Forest Consolidation: Move files to unified layout

Reviewed-by: darcy, ihse

src/java.base/share/classes/java/util/Deque.java

@@ -0,0 +1,616 @@
+/*
+ * 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 and Josh Bloch 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;
+
+/**
+ * A linear collection that supports element insertion and removal at
+ * both ends.  The name <i>deque</i> is short for "double ended queue"
+ * and is usually pronounced "deck".  Most {@code Deque}
+ * implementations place no fixed limits on the number of elements
+ * they may contain, but this interface supports capacity-restricted
+ * deques as well as those with no fixed size limit.
+ *
+ * <p>This interface defines methods to access the elements at both
+ * ends of the deque.  Methods are provided to insert, remove, and
+ * examine the element.  Each of these methods exists in two forms:
+ * one throws an exception if the operation fails, the other returns a
+ * special value (either {@code null} or {@code false}, depending on
+ * the operation).  The latter form of the insert operation is
+ * designed specifically for use with capacity-restricted
+ * {@code Deque} implementations; in most implementations, insert
+ * operations cannot fail.
+ *
+ * <p>The twelve methods described above are summarized in the
+ * following table:
+ *
+ * <table class="striped">
+ * <caption>Summary of Deque methods</caption>
+ *  <thead>
+ *  <tr>
+ *    <td rowspan="2"></td>
+ *    <th scope="col" colspan="2"> First Element (Head)</th>
+ *    <th scope="col" colspan="2"> Last Element (Tail)</th>
+ *  </tr>
+ *  <tr>
+ *    <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">Throws exception</th>
+ *    <th scope="col" style="font-weight:normal; font-style:italic">Special value</th>
+ *  </tr>
+ *  </thead>
+ *  <tbody>
+ *  <tr>
+ *    <th scope="row">Insert</th>
+ *    <td>{@link #addFirst(Object) addFirst(e)}</td>
+ *    <td>{@link #offerFirst(Object) offerFirst(e)}</td>
+ *    <td>{@link #addLast(Object) addLast(e)}</td>
+ *    <td>{@link #offerLast(Object) offerLast(e)}</td>
+ *  </tr>
+ *  <tr>
+ *    <th scope="row">Remove</th>
+ *    <td>{@link #removeFirst() removeFirst()}</td>
+ *    <td>{@link #pollFirst() pollFirst()}</td>
+ *    <td>{@link #removeLast() removeLast()}</td>
+ *    <td>{@link #pollLast() pollLast()}</td>
+ *  </tr>
+ *  <tr>
+ *    <th scope="row">Examine</th>
+ *    <td>{@link #getFirst() getFirst()}</td>
+ *    <td>{@link #peekFirst() peekFirst()}</td>
+ *    <td>{@link #getLast() getLast()}</td>
+ *    <td>{@link #peekLast() peekLast()}</td>
+ *  </tr>
+ *  </tbody>
+ * </table>
+ *
+ * <p>This interface extends the {@link Queue} interface.  When a deque is
+ * used as a queue, FIFO (First-In-First-Out) behavior results.  Elements are
+ * added at the end of the deque and removed from the beginning.  The methods
+ * inherited from the {@code Queue} interface are precisely equivalent to
+ * {@code Deque} methods as indicated in the following table:
+ *
+ * <table class="striped">
+ * <caption>Comparison of Queue and Deque methods</caption>
+ *  <thead>
+ *  <tr>
+ *    <th scope="col"> {@code Queue} Method</th>
+ *    <th scope="col"> Equivalent {@code Deque} Method</th>
+ *  </tr>
+ *  </thead>
+ *  <tbody>
+ *  <tr>
+ *    <th scope="row">{@link #add(Object) add(e)}</th>
+ *    <td>{@link #addLast(Object) addLast(e)}</td>
+ *  </tr>
+ *  <tr>
+ *    <th scope="row">{@link #offer(Object) offer(e)}</th>
+ *    <td>{@link #offerLast(Object) offerLast(e)}</td>
+ *  </tr>
+ *  <tr>
+ *    <th scope="row">{@link #remove() remove()}</th>
+ *    <td>{@link #removeFirst() removeFirst()}</td>
+ *  </tr>
+ *  <tr>
+ *    <th scope="row">{@link #poll() poll()}</th>
+ *    <td>{@link #pollFirst() pollFirst()}</td>
+ *  </tr>
+ *  <tr>
+ *    <th scope="row">{@link #element() element()}</th>
+ *    <td>{@link #getFirst() getFirst()}</td>
+ *  </tr>
+ *  <tr>
+ *    <th scope="row">{@link #peek() peek()}</th>
+ *    <td>{@link #peekFirst() peekFirst()}</td>
+ *  </tr>
+ *  </tbody>
+ * </table>
+ *
+ * <p>Deques can also be used as LIFO (Last-In-First-Out) stacks.  This
+ * interface should be used in preference to the legacy {@link Stack} class.
+ * When a deque is used as a stack, elements are pushed and popped from the
+ * beginning of the deque.  Stack methods are precisely equivalent to
+ * {@code Deque} methods as indicated in the table below:
+ *
+ * <table class="striped">
+ * <caption>Comparison of Stack and Deque methods</caption>
+ *  <thead>
+ *  <tr>
+ *    <th scope="col"> Stack Method</th>
+ *    <th scope="col"> Equivalent {@code Deque} Method</th>
+ *  </tr>
+ *  </thead>
+ *  <tbody>
+ *  <tr>
+ *    <th scope="row">{@link #push(Object) push(e)}</th>
+ *    <td>{@link #addFirst(Object) addFirst(e)}</td>
+ *  </tr>
+ *  <tr>
+ *    <th scope="row">{@link #pop() pop()}</th>
+ *    <td>{@link #removeFirst() removeFirst()}</td>
+ *  </tr>
+ *  <tr>
+ *    <th scope="row">{@link #peek() peek()}</th>
+ *    <td>{@link #peekFirst() peekFirst()}</td>
+ *  </tr>
+ *  </tbody>
+ * </table>
+ *
+ * <p>Note that the {@link #peek peek} method works equally well when
+ * a deque is used as a queue or a stack; in either case, elements are
+ * drawn from the beginning of the deque.
+ *
+ * <p>This interface provides two methods to remove interior
+ * elements, {@link #removeFirstOccurrence removeFirstOccurrence} and
+ * {@link #removeLastOccurrence removeLastOccurrence}.
+ *
+ * <p>Unlike the {@link List} interface, this interface does not
+ * provide support for indexed access to elements.
+ *
+ * <p>While {@code Deque} implementations are not strictly required
+ * to prohibit the insertion of null elements, they are strongly
+ * encouraged to do so.  Users of any {@code Deque} implementations
+ * that do allow null elements are strongly encouraged <i>not</i> to
+ * take advantage of the ability to insert nulls.  This is so because
+ * {@code null} is used as a special return value by various methods
+ * to indicate that the deque is empty.
+ *
+ * <p>{@code Deque} implementations generally do not define
+ * element-based versions of the {@code equals} and {@code hashCode}
+ * methods, but instead inherit the identity-based versions from class
+ * {@code Object}.
+ *
+ * <p>This interface is a member of the
+ * <a href="{@docRoot}/java/util/package-summary.html#CollectionsFramework">
+ * Java Collections Framework</a>.
+ *
+ * @author Doug Lea
+ * @author Josh Bloch
+ * @since  1.6
+ * @param <E> the type of elements held in this deque
+ */
+public interface Deque<E> extends Queue<E> {
+    /**
+     * 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 method {@link #offerFirst}.
+     *
+     * @param e the element to 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 deque
+     * @throws NullPointerException if the specified element is null and this
+     *         deque does not permit null elements
+     * @throws IllegalArgumentException if some property of the specified
+     *         element prevents it from being added to this deque
+     */
+    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 method {@link #offerLast}.
+     *
+     * <p>This method is equivalent to {@link #add}.
+     *
+     * @param e the element to 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 deque
+     * @throws NullPointerException if the specified element is null and this
+     *         deque does not permit null elements
+     * @throws IllegalArgumentException if some property of the specified
+     *         element prevents it from being added to this deque
+     */
+    void addLast(E e);
+
+    /**
+     * Inserts the specified element at the front of this deque unless it would
+     * violate capacity restrictions.  When using a capacity-restricted deque,
+     * this method is generally preferable to the {@link #addFirst} method,
+     * 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 deque, else
+     *         {@code false}
+     * @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 and this
+     *         deque does not permit null elements
+     * @throws IllegalArgumentException if some property of the specified
+     *         element prevents it from being added to this deque
+     */
+    boolean offerFirst(E e);
+
+    /**
+     * Inserts the specified element at the end of this deque unless it would
+     * violate capacity restrictions.  When using a capacity-restricted deque,
+     * this method is generally preferable to the {@link #addLast} method,
+     * 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 deque, else
+     *         {@code false}
+     * @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 and this
+     *         deque does not permit null elements
+     * @throws IllegalArgumentException if some property of the specified
+     *         element prevents it from being added to this deque
+     */
+    boolean offerLast(E e);
+
+    /**
+     * Retrieves and removes the first element of this deque.  This method
+     * differs from {@link #pollFirst pollFirst} only in that it throws an
+     * exception if this deque is empty.
+     *
+     * @return the head of this deque
+     * @throws NoSuchElementException if this deque is empty
+     */
+    E removeFirst();
+
+    /**
+     * Retrieves and removes the last element of this deque.  This method
+     * differs from {@link #pollLast pollLast} only in that it throws an
+     * exception if this deque is empty.
+     *
+     * @return the tail of this deque
+     * @throws NoSuchElementException if this deque is empty
+     */
+    E removeLast();
+
+    /**
+     * Retrieves and removes the first element of this deque,
+     * or returns {@code null} if this deque is empty.
+     *
+     * @return the head of this deque, or {@code null} if this deque is empty
+     */
+    E pollFirst();
+
+    /**
+     * Retrieves and removes the last element of this deque,
+     * or returns {@code null} if this deque is empty.
+     *
+     * @return the tail of this deque, or {@code null} if this deque is empty
+     */
+    E pollLast();
+
+    /**
+     * Retrieves, but does not remove, the first element of this deque.
+     *
+     * This method differs from {@link #peekFirst peekFirst} only in that it
+     * throws an exception if this deque is empty.
+     *
+     * @return the head of this deque
+     * @throws NoSuchElementException if this deque is empty
+     */
+    E getFirst();
+
+    /**
+     * Retrieves, but does not remove, the last element of this deque.
+     * This method differs from {@link #peekLast peekLast} only in that it
+     * throws an exception if this deque is empty.
+     *
+     * @return the tail of this deque
+     * @throws NoSuchElementException if this deque is empty
+     */
+    E getLast();
+
+    /**
+     * Retrieves, but does not remove, the first element of this deque,
+     * or returns {@code null} if this deque is empty.
+     *
+     * @return the head of this deque, or {@code null} if this deque is empty
+     */
+    E peekFirst();
+
+    /**
+     * Retrieves, but does not remove, the last element of this deque,
+     * or returns {@code null} if this deque is empty.
+     *
+     * @return the tail of this deque, or {@code null} if this deque is empty
+     */
+    E peekLast();
+
+    /**
+     * 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 Objects.equals(o, 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 and this
+     *         deque does not permit null elements
+     * (<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 Objects.equals(o, 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 and this
+     *         deque does not permit null elements
+     * (<a href="{@docRoot}/java/util/Collection.html#optional-restrictions">optional</a>)
+     */
+    boolean removeLastOccurrence(Object o);
+
+    // *** Queue 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}.
+     *
+     * @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 deque
+     * @throws NullPointerException if the specified element is null and this
+     *         deque does not permit null elements
+     * @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}.
+     *
+     * @param e the element to add
+     * @return {@code true} if the element was added to this deque, else
+     *         {@code false}
+     * @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 and this
+     *         deque does not permit null elements
+     * @throws IllegalArgumentException if some property of the specified
+     *         element prevents it from being added to this deque
+     */
+    boolean offer(E e);
+
+    /**
+     * 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()}.
+     *
+     * @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 first element of this deque, or {@code null} if
+     *         this deque is empty
+     */
+    E poll();
+
+    /**
+     * 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()}.
+     *
+     * @return the head of the queue represented by 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()}.
+     *
+     * @return the head of the queue represented by this deque, or
+     *         {@code null} if this deque is empty
+     */
+    E peek();
+
+    /**
+     * Adds all of the elements in the specified collection at the end
+     * of this deque, as if by calling {@link #addLast} on each one,
+     * in the order that they are returned by the collection's iterator.
+     *
+     * <p>When using a capacity-restricted deque, it is generally preferable
+     * to call {@link #offer(Object) offer} separately on each element.
+     *
+     * <p>An exception encountered while trying to add an element may result
+     * in only some of the elements having been successfully added when
+     * the associated exception is thrown.
+     *
+     * @param c the elements to be inserted into this deque
+     * @return {@code true} if this deque changed as a result of the call
+     * @throws IllegalStateException if not all the elements can be added at
+     *         this time due to insertion restrictions
+     * @throws ClassCastException if the class of an element of the specified
+     *         collection prevents it from being added to this deque
+     * @throws NullPointerException if the specified collection contains a
+     *         null element and this deque does not permit null elements,
+     *         or if the specified collection is null
+     * @throws IllegalArgumentException if some property of an element of the
+     *         specified collection prevents it from being added to this deque
+     */
+    boolean addAll(Collection<? extends E> c);
+
+    // *** 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}.
+     *
+     * @param e the element to push
+     * @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 deque
+     * @throws NullPointerException if the specified element is null and this
+     *         deque does not permit null elements
+     * @throws IllegalArgumentException if some property of the specified
+     *         element prevents it from being added to this deque
+     */
+    void push(E e);
+
+    /**
+     * Pops an element from the stack represented by this deque.  In other
+     * words, removes and returns the first element of this deque.
+     *
+     * <p>This method is equivalent to {@link #removeFirst()}.
+     *
+     * @return the element at the front of this deque (which is the top
+     *         of the stack represented by this deque)
+     * @throws NoSuchElementException if this deque is empty
+     */
+    E pop();
+
+
+    // *** Collection methods ***
+
+    /**
+     * 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 Objects.equals(o, 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)}.
+     *
+     * @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 and this
+     *         deque does not permit null elements
+     * (<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 Objects.equals(o, e)}.
+     *
+     * @param o element whose presence in this deque is to be tested
+     * @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 and this
+     *         deque does not permit null elements
+     * (<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();
+
+    /**
+     * Returns an iterator over the elements in this deque in reverse
+     * sequential order.  The elements will be returned in order from
+     * last (tail) to first (head).
+     *
+     * @return an iterator over the elements in this deque in reverse
+     * sequence
+     */
+    Iterator<E> descendingIterator();
+
+}