| /* |
| * 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.base/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.base/java/util/Collection.html#optional-restrictions">optional</a>) |
| * @throws NullPointerException if the specified element is null |
| * (<a href="{@docRoot}/java.base/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.base/java/util/Collection.html#optional-restrictions">optional</a>) |
| * @throws NullPointerException if the specified element is null |
| * (<a href="{@docRoot}/java.base/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.base/java/util/Collection.html#optional-restrictions">optional</a>) |
| * @throws NullPointerException if the specified element is null |
| * (<a href="{@docRoot}/java.base/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.base/java/util/Collection.html#optional-restrictions">optional</a>) |
| * @throws NullPointerException if the specified element is null |
| * (<a href="{@docRoot}/java.base/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); |
| } |
