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/* |
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* Written by Doug Lea with assistance from members of JCP JSR-166 |
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* Expert Group and released to the public domain, as explained at |
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* http://creativecommons.org/publicdomain/zero/1.0/ |
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*/ |
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package java.util.concurrent; |
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import java.util.*; |
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/** |
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* A {@link Deque} that additionally supports blocking operations that wait |
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* for the deque to become non-empty when retrieving an element, and wait for |
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* space to become available in the deque when storing an element. |
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* |
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jsr166 |
1.2 |
* <p>{@code BlockingDeque} methods come in four forms, with different ways |
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1.1 |
* of handling operations that cannot be satisfied immediately, but may be |
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* satisfied at some point in the future: |
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* one throws an exception, the second returns a special value (either |
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jsr166 |
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* {@code null} or {@code false}, depending on the operation), the third |
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* blocks the current thread indefinitely until the operation can succeed, |
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* and the fourth blocks for only a given maximum time limit before giving |
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* up. These methods are summarized in the following table: |
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* |
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* <p> |
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* <table BORDER CELLPADDING=3 CELLSPACING=1> |
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1.3 |
* <caption>Summary of BlockingDeque methods</caption> |
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1.1 |
* <tr> |
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* <td ALIGN=CENTER COLSPAN = 5> <b>First Element (Head)</b></td> |
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* </tr> |
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* <tr> |
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* <td></td> |
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* <td ALIGN=CENTER><em>Throws exception</em></td> |
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* <td ALIGN=CENTER><em>Special value</em></td> |
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* <td ALIGN=CENTER><em>Blocks</em></td> |
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* <td ALIGN=CENTER><em>Times out</em></td> |
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* </tr> |
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* <tr> |
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* <td><b>Insert</b></td> |
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* <td>{@link #addFirst addFirst(e)}</td> |
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* <td>{@link #offerFirst(Object) offerFirst(e)}</td> |
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* <td>{@link #putFirst putFirst(e)}</td> |
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* <td>{@link #offerFirst(Object, long, TimeUnit) offerFirst(e, time, unit)}</td> |
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* </tr> |
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* <tr> |
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* <td><b>Remove</b></td> |
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* <td>{@link #removeFirst removeFirst()}</td> |
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* <td>{@link #pollFirst pollFirst()}</td> |
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* <td>{@link #takeFirst takeFirst()}</td> |
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* <td>{@link #pollFirst(long, TimeUnit) pollFirst(time, unit)}</td> |
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* </tr> |
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* <tr> |
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* <td><b>Examine</b></td> |
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* <td>{@link #getFirst getFirst()}</td> |
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* <td>{@link #peekFirst peekFirst()}</td> |
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* <td><em>not applicable</em></td> |
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* <td><em>not applicable</em></td> |
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* </tr> |
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* <tr> |
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* <td ALIGN=CENTER COLSPAN = 5> <b>Last Element (Tail)</b></td> |
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* </tr> |
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* <tr> |
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* <td></td> |
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* <td ALIGN=CENTER><em>Throws exception</em></td> |
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* <td ALIGN=CENTER><em>Special value</em></td> |
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* <td ALIGN=CENTER><em>Blocks</em></td> |
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* <td ALIGN=CENTER><em>Times out</em></td> |
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* </tr> |
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* <tr> |
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* <td><b>Insert</b></td> |
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* <td>{@link #addLast addLast(e)}</td> |
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* <td>{@link #offerLast(Object) offerLast(e)}</td> |
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* <td>{@link #putLast putLast(e)}</td> |
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* <td>{@link #offerLast(Object, long, TimeUnit) offerLast(e, time, unit)}</td> |
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* </tr> |
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* <tr> |
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* <td><b>Remove</b></td> |
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* <td>{@link #removeLast() removeLast()}</td> |
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* <td>{@link #pollLast() pollLast()}</td> |
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* <td>{@link #takeLast takeLast()}</td> |
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* <td>{@link #pollLast(long, TimeUnit) pollLast(time, unit)}</td> |
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* </tr> |
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* <tr> |
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* <td><b>Examine</b></td> |
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* <td>{@link #getLast getLast()}</td> |
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* <td>{@link #peekLast peekLast()}</td> |
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* <td><em>not applicable</em></td> |
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* <td><em>not applicable</em></td> |
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* </tr> |
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* </table> |
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* |
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jsr166 |
1.2 |
* <p>Like any {@link BlockingQueue}, a {@code BlockingDeque} is thread safe, |
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1.1 |
* does not permit null elements, and may (or may not) be |
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* capacity-constrained. |
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* |
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jsr166 |
1.2 |
* <p>A {@code BlockingDeque} implementation may be used directly as a FIFO |
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* {@code BlockingQueue}. The methods inherited from the |
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* {@code BlockingQueue} interface are precisely equivalent to |
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* {@code BlockingDeque} methods as indicated in the following table: |
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1.1 |
* |
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* <p> |
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* <table BORDER CELLPADDING=3 CELLSPACING=1> |
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jsr166 |
1.3 |
* <caption>Comparison of BlockingQueue and BlockingDeque methods</caption> |
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dl |
1.1 |
* <tr> |
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jsr166 |
1.2 |
* <td ALIGN=CENTER> <b>{@code BlockingQueue} Method</b></td> |
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* <td ALIGN=CENTER> <b>Equivalent {@code BlockingDeque} Method</b></td> |
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dl |
1.1 |
* </tr> |
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* <tr> |
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* <td ALIGN=CENTER COLSPAN = 2> <b>Insert</b></td> |
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* </tr> |
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* <tr> |
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* <td>{@link #add(Object) add(e)}</td> |
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* <td>{@link #addLast(Object) addLast(e)}</td> |
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* </tr> |
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* <tr> |
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* <td>{@link #offer(Object) offer(e)}</td> |
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* <td>{@link #offerLast(Object) offerLast(e)}</td> |
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* </tr> |
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* <tr> |
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* <td>{@link #put(Object) put(e)}</td> |
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* <td>{@link #putLast(Object) putLast(e)}</td> |
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* </tr> |
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* <tr> |
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* <td>{@link #offer(Object, long, TimeUnit) offer(e, time, unit)}</td> |
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* <td>{@link #offerLast(Object, long, TimeUnit) offerLast(e, time, unit)}</td> |
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* </tr> |
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* <tr> |
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* <td ALIGN=CENTER COLSPAN = 2> <b>Remove</b></td> |
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* </tr> |
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* <tr> |
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* <td>{@link #remove() remove()}</td> |
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* <td>{@link #removeFirst() removeFirst()}</td> |
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* </tr> |
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* <tr> |
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* <td>{@link #poll() poll()}</td> |
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* <td>{@link #pollFirst() pollFirst()}</td> |
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* </tr> |
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* <tr> |
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* <td>{@link #take() take()}</td> |
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* <td>{@link #takeFirst() takeFirst()}</td> |
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* </tr> |
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* <tr> |
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* <td>{@link #poll(long, TimeUnit) poll(time, unit)}</td> |
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* <td>{@link #pollFirst(long, TimeUnit) pollFirst(time, unit)}</td> |
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* </tr> |
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* <tr> |
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* <td ALIGN=CENTER COLSPAN = 2> <b>Examine</b></td> |
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* </tr> |
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* <tr> |
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* <td>{@link #element() element()}</td> |
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* <td>{@link #getFirst() getFirst()}</td> |
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* </tr> |
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* <tr> |
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* <td>{@link #peek() peek()}</td> |
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* <td>{@link #peekFirst() peekFirst()}</td> |
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* </tr> |
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* </table> |
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* |
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* <p>Memory consistency effects: As with other concurrent |
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* collections, actions in a thread prior to placing an object into a |
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* {@code BlockingDeque} |
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* <a href="package-summary.html#MemoryVisibility"><i>happen-before</i></a> |
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* actions subsequent to the access or removal of that element from |
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* the {@code BlockingDeque} in another thread. |
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* |
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* <p>This interface is a member of the |
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* <a href="{@docRoot}/../technotes/guides/collections/index.html"> |
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* Java Collections Framework</a>. |
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* |
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* @since 1.6 |
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* @author Doug Lea |
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* @param <E> the type of elements held in this collection |
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*/ |
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public interface BlockingDeque<E> extends BlockingQueue<E>, Deque<E> { |
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/* |
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* We have "diamond" multiple interface inheritance here, and that |
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* introduces ambiguities. Methods might end up with different |
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* specs depending on the branch chosen by javadoc. Thus a lot of |
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* methods specs here are copied from superinterfaces. |
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*/ |
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/** |
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* Inserts the specified element at the front of this deque if it is |
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* possible to do so immediately without violating capacity restrictions, |
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jsr166 |
1.2 |
* throwing an {@code IllegalStateException} if no space is currently |
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dl |
1.1 |
* available. When using a capacity-restricted deque, it is generally |
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* preferable to use {@link #offerFirst(Object) offerFirst}. |
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* |
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* @param e the element to add |
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* @throws IllegalStateException {@inheritDoc} |
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* @throws ClassCastException {@inheritDoc} |
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* @throws NullPointerException if the specified element is null |
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* @throws IllegalArgumentException {@inheritDoc} |
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*/ |
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void addFirst(E e); |
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/** |
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* Inserts the specified element at the end of this deque if it is |
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* possible to do so immediately without violating capacity restrictions, |
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jsr166 |
1.2 |
* throwing an {@code IllegalStateException} if no space is currently |
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1.1 |
* available. When using a capacity-restricted deque, it is generally |
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* preferable to use {@link #offerLast(Object) offerLast}. |
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* |
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* @param e the element to add |
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* @throws IllegalStateException {@inheritDoc} |
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* @throws ClassCastException {@inheritDoc} |
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* @throws NullPointerException if the specified element is null |
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* @throws IllegalArgumentException {@inheritDoc} |
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*/ |
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void addLast(E e); |
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/** |
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* Inserts the specified element at the front of this deque if it is |
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* possible to do so immediately without violating capacity restrictions, |
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jsr166 |
1.2 |
* returning {@code true} upon success and {@code false} if no space is |
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dl |
1.1 |
* currently available. |
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* When using a capacity-restricted deque, this method is generally |
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* preferable to the {@link #addFirst(Object) addFirst} method, which can |
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* fail to insert an element only by throwing an exception. |
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* |
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* @param e the element to add |
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* @throws ClassCastException {@inheritDoc} |
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* @throws NullPointerException if the specified element is null |
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* @throws IllegalArgumentException {@inheritDoc} |
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*/ |
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boolean offerFirst(E e); |
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/** |
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* Inserts the specified element at the end of this deque if it is |
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* possible to do so immediately without violating capacity restrictions, |
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jsr166 |
1.2 |
* returning {@code true} upon success and {@code false} if no space is |
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dl |
1.1 |
* currently available. |
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* When using a capacity-restricted deque, this method is generally |
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* preferable to the {@link #addLast(Object) addLast} method, which can |
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* fail to insert an element only by throwing an exception. |
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* |
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* @param e the element to add |
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* @throws ClassCastException {@inheritDoc} |
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* @throws NullPointerException if the specified element is null |
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* @throws IllegalArgumentException {@inheritDoc} |
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*/ |
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boolean offerLast(E e); |
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/** |
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* Inserts the specified element at the front of this deque, |
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* waiting if necessary for space to become available. |
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* |
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* @param e the element to add |
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* @throws InterruptedException if interrupted while waiting |
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* @throws ClassCastException if the class of the specified element |
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* prevents it from being added to this deque |
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* @throws NullPointerException if the specified element is null |
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* @throws IllegalArgumentException if some property of the specified |
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* element prevents it from being added to this deque |
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*/ |
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void putFirst(E e) throws InterruptedException; |
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/** |
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* Inserts the specified element at the end of this deque, |
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* waiting if necessary for space to become available. |
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* |
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* @param e the element to add |
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* @throws InterruptedException if interrupted while waiting |
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* @throws ClassCastException if the class of the specified element |
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* prevents it from being added to this deque |
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* @throws NullPointerException if the specified element is null |
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* @throws IllegalArgumentException if some property of the specified |
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* element prevents it from being added to this deque |
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*/ |
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void putLast(E e) throws InterruptedException; |
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/** |
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* Inserts the specified element at the front of this deque, |
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* waiting up to the specified wait time if necessary for space to |
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* become available. |
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* |
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* @param e the element to add |
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* @param timeout how long to wait before giving up, in units of |
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jsr166 |
1.2 |
* {@code unit} |
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* @param unit a {@code TimeUnit} determining how to interpret the |
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* {@code timeout} parameter |
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* @return {@code true} if successful, or {@code false} if |
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1.1 |
* the specified waiting time elapses before space is available |
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* @throws InterruptedException if interrupted while waiting |
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* @throws ClassCastException if the class of the specified element |
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* prevents it from being added to this deque |
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* @throws NullPointerException if the specified element is null |
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* @throws IllegalArgumentException if some property of the specified |
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* element prevents it from being added to this deque |
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*/ |
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boolean offerFirst(E e, long timeout, TimeUnit unit) |
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throws InterruptedException; |
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/** |
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* Inserts the specified element at the end of this deque, |
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* waiting up to the specified wait time if necessary for space to |
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* become available. |
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* |
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* @param e the element to add |
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* @param timeout how long to wait before giving up, in units of |
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jsr166 |
1.2 |
* {@code unit} |
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* @param unit a {@code TimeUnit} determining how to interpret the |
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* {@code timeout} parameter |
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* @return {@code true} if successful, or {@code false} if |
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dl |
1.1 |
* the specified waiting time elapses before space is available |
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* @throws InterruptedException if interrupted while waiting |
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* @throws ClassCastException if the class of the specified element |
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* prevents it from being added to this deque |
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* @throws NullPointerException if the specified element is null |
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* @throws IllegalArgumentException if some property of the specified |
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* element prevents it from being added to this deque |
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*/ |
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boolean offerLast(E e, long timeout, TimeUnit unit) |
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throws InterruptedException; |
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/** |
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* Retrieves and removes the first element of this deque, waiting |
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* if necessary until an element becomes available. |
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* |
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* @return the head of this deque |
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* @throws InterruptedException if interrupted while waiting |
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*/ |
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E takeFirst() throws InterruptedException; |
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/** |
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* Retrieves and removes the last element of this deque, waiting |
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* if necessary until an element becomes available. |
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* |
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* @return the tail of this deque |
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* @throws InterruptedException if interrupted while waiting |
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*/ |
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E takeLast() throws InterruptedException; |
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/** |
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* Retrieves and removes the first element of this deque, waiting |
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* up to the specified wait time if necessary for an element to |
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* become available. |
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* |
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* @param timeout how long to wait before giving up, in units of |
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jsr166 |
1.2 |
* {@code unit} |
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* @param unit a {@code TimeUnit} determining how to interpret the |
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* {@code timeout} parameter |
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* @return the head of this deque, or {@code null} if the specified |
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dl |
1.1 |
* waiting time elapses before an element is available |
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* @throws InterruptedException if interrupted while waiting |
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*/ |
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E pollFirst(long timeout, TimeUnit unit) |
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throws InterruptedException; |
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/** |
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* Retrieves and removes the last element of this deque, waiting |
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* up to the specified wait time if necessary for an element to |
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|
|
* become available. |
353 |
|
|
* |
354 |
|
|
* @param timeout how long to wait before giving up, in units of |
355 |
jsr166 |
1.2 |
* {@code unit} |
356 |
|
|
* @param unit a {@code TimeUnit} determining how to interpret the |
357 |
|
|
* {@code timeout} parameter |
358 |
|
|
* @return the tail of this deque, or {@code null} if the specified |
359 |
dl |
1.1 |
* waiting time elapses before an element is available |
360 |
|
|
* @throws InterruptedException if interrupted while waiting |
361 |
|
|
*/ |
362 |
|
|
E pollLast(long timeout, TimeUnit unit) |
363 |
|
|
throws InterruptedException; |
364 |
|
|
|
365 |
|
|
/** |
366 |
|
|
* Removes the first occurrence of the specified element from this deque. |
367 |
|
|
* If the deque does not contain the element, it is unchanged. |
368 |
jsr166 |
1.2 |
* More formally, removes the first element {@code e} such that |
369 |
|
|
* {@code o.equals(e)} (if such an element exists). |
370 |
|
|
* Returns {@code true} if this deque contained the specified element |
371 |
dl |
1.1 |
* (or equivalently, if this deque changed as a result of the call). |
372 |
|
|
* |
373 |
|
|
* @param o element to be removed from this deque, if present |
374 |
jsr166 |
1.2 |
* @return {@code true} if an element was removed as a result of this call |
375 |
dl |
1.1 |
* @throws ClassCastException if the class of the specified element |
376 |
|
|
* is incompatible with this deque |
377 |
|
|
* (<a href="../Collection.html#optional-restrictions">optional</a>) |
378 |
|
|
* @throws NullPointerException if the specified element is null |
379 |
|
|
* (<a href="../Collection.html#optional-restrictions">optional</a>) |
380 |
|
|
*/ |
381 |
|
|
boolean removeFirstOccurrence(Object o); |
382 |
|
|
|
383 |
|
|
/** |
384 |
|
|
* Removes the last occurrence of the specified element from this deque. |
385 |
|
|
* If the deque does not contain the element, it is unchanged. |
386 |
jsr166 |
1.2 |
* More formally, removes the last element {@code e} such that |
387 |
|
|
* {@code o.equals(e)} (if such an element exists). |
388 |
|
|
* Returns {@code true} if this deque contained the specified element |
389 |
dl |
1.1 |
* (or equivalently, if this deque changed as a result of the call). |
390 |
|
|
* |
391 |
|
|
* @param o element to be removed from this deque, if present |
392 |
jsr166 |
1.2 |
* @return {@code true} if an element was removed as a result of this call |
393 |
dl |
1.1 |
* @throws ClassCastException if the class of the specified element |
394 |
|
|
* is incompatible with this deque |
395 |
|
|
* (<a href="../Collection.html#optional-restrictions">optional</a>) |
396 |
|
|
* @throws NullPointerException if the specified element is null |
397 |
|
|
* (<a href="../Collection.html#optional-restrictions">optional</a>) |
398 |
|
|
*/ |
399 |
|
|
boolean removeLastOccurrence(Object o); |
400 |
|
|
|
401 |
|
|
// *** BlockingQueue methods *** |
402 |
|
|
|
403 |
|
|
/** |
404 |
|
|
* Inserts the specified element into the queue represented by this deque |
405 |
|
|
* (in other words, at the tail of this deque) if it is possible to do so |
406 |
|
|
* immediately without violating capacity restrictions, returning |
407 |
jsr166 |
1.2 |
* {@code true} upon success and throwing an |
408 |
|
|
* {@code IllegalStateException} if no space is currently available. |
409 |
dl |
1.1 |
* When using a capacity-restricted deque, it is generally preferable to |
410 |
|
|
* use {@link #offer(Object) offer}. |
411 |
|
|
* |
412 |
|
|
* <p>This method is equivalent to {@link #addLast(Object) addLast}. |
413 |
|
|
* |
414 |
|
|
* @param e the element to add |
415 |
|
|
* @throws IllegalStateException {@inheritDoc} |
416 |
|
|
* @throws ClassCastException if the class of the specified element |
417 |
|
|
* prevents it from being added to this deque |
418 |
|
|
* @throws NullPointerException if the specified element is null |
419 |
|
|
* @throws IllegalArgumentException if some property of the specified |
420 |
|
|
* element prevents it from being added to this deque |
421 |
|
|
*/ |
422 |
|
|
boolean add(E e); |
423 |
|
|
|
424 |
|
|
/** |
425 |
|
|
* Inserts the specified element into the queue represented by this deque |
426 |
|
|
* (in other words, at the tail of this deque) if it is possible to do so |
427 |
|
|
* immediately without violating capacity restrictions, returning |
428 |
jsr166 |
1.2 |
* {@code true} upon success and {@code false} if no space is currently |
429 |
dl |
1.1 |
* available. When using a capacity-restricted deque, this method is |
430 |
|
|
* generally preferable to the {@link #add} method, which can fail to |
431 |
|
|
* insert an element only by throwing an exception. |
432 |
|
|
* |
433 |
|
|
* <p>This method is equivalent to {@link #offerLast(Object) offerLast}. |
434 |
|
|
* |
435 |
|
|
* @param e the element to add |
436 |
|
|
* @throws ClassCastException if the class of the specified element |
437 |
|
|
* prevents it from being added to this deque |
438 |
|
|
* @throws NullPointerException if the specified element is null |
439 |
|
|
* @throws IllegalArgumentException if some property of the specified |
440 |
|
|
* element prevents it from being added to this deque |
441 |
|
|
*/ |
442 |
|
|
boolean offer(E e); |
443 |
|
|
|
444 |
|
|
/** |
445 |
|
|
* Inserts the specified element into the queue represented by this deque |
446 |
|
|
* (in other words, at the tail of this deque), waiting if necessary for |
447 |
|
|
* space to become available. |
448 |
|
|
* |
449 |
|
|
* <p>This method is equivalent to {@link #putLast(Object) putLast}. |
450 |
|
|
* |
451 |
|
|
* @param e the element to add |
452 |
|
|
* @throws InterruptedException {@inheritDoc} |
453 |
|
|
* @throws ClassCastException if the class of the specified element |
454 |
|
|
* prevents it from being added to this deque |
455 |
|
|
* @throws NullPointerException if the specified element is null |
456 |
|
|
* @throws IllegalArgumentException if some property of the specified |
457 |
|
|
* element prevents it from being added to this deque |
458 |
|
|
*/ |
459 |
|
|
void put(E e) throws InterruptedException; |
460 |
|
|
|
461 |
|
|
/** |
462 |
|
|
* Inserts the specified element into the queue represented by this deque |
463 |
|
|
* (in other words, at the tail of this deque), waiting up to the |
464 |
|
|
* specified wait time if necessary for space to become available. |
465 |
|
|
* |
466 |
|
|
* <p>This method is equivalent to |
467 |
|
|
* {@link #offerLast(Object,long,TimeUnit) offerLast}. |
468 |
|
|
* |
469 |
|
|
* @param e the element to add |
470 |
jsr166 |
1.2 |
* @return {@code true} if the element was added to this deque, else |
471 |
|
|
* {@code false} |
472 |
dl |
1.1 |
* @throws InterruptedException {@inheritDoc} |
473 |
|
|
* @throws ClassCastException if the class of the specified element |
474 |
|
|
* prevents it from being added to this deque |
475 |
|
|
* @throws NullPointerException if the specified element is null |
476 |
|
|
* @throws IllegalArgumentException if some property of the specified |
477 |
|
|
* element prevents it from being added to this deque |
478 |
|
|
*/ |
479 |
|
|
boolean offer(E e, long timeout, TimeUnit unit) |
480 |
|
|
throws InterruptedException; |
481 |
|
|
|
482 |
|
|
/** |
483 |
|
|
* Retrieves and removes the head of the queue represented by this deque |
484 |
|
|
* (in other words, the first element of this deque). |
485 |
|
|
* This method differs from {@link #poll poll} only in that it |
486 |
|
|
* throws an exception if this deque is empty. |
487 |
|
|
* |
488 |
|
|
* <p>This method is equivalent to {@link #removeFirst() removeFirst}. |
489 |
|
|
* |
490 |
|
|
* @return the head of the queue represented by this deque |
491 |
|
|
* @throws NoSuchElementException if this deque is empty |
492 |
|
|
*/ |
493 |
|
|
E remove(); |
494 |
|
|
|
495 |
|
|
/** |
496 |
|
|
* Retrieves and removes the head of the queue represented by this deque |
497 |
|
|
* (in other words, the first element of this deque), or returns |
498 |
jsr166 |
1.2 |
* {@code null} if this deque is empty. |
499 |
dl |
1.1 |
* |
500 |
|
|
* <p>This method is equivalent to {@link #pollFirst()}. |
501 |
|
|
* |
502 |
jsr166 |
1.2 |
* @return the head of this deque, or {@code null} if this deque is empty |
503 |
dl |
1.1 |
*/ |
504 |
|
|
E poll(); |
505 |
|
|
|
506 |
|
|
/** |
507 |
|
|
* Retrieves and removes the head of the queue represented by this deque |
508 |
|
|
* (in other words, the first element of this deque), waiting if |
509 |
|
|
* necessary until an element becomes available. |
510 |
|
|
* |
511 |
|
|
* <p>This method is equivalent to {@link #takeFirst() takeFirst}. |
512 |
|
|
* |
513 |
|
|
* @return the head of this deque |
514 |
|
|
* @throws InterruptedException if interrupted while waiting |
515 |
|
|
*/ |
516 |
|
|
E take() throws InterruptedException; |
517 |
|
|
|
518 |
|
|
/** |
519 |
|
|
* Retrieves and removes the head of the queue represented by this deque |
520 |
|
|
* (in other words, the first element of this deque), waiting up to the |
521 |
|
|
* specified wait time if necessary for an element to become available. |
522 |
|
|
* |
523 |
|
|
* <p>This method is equivalent to |
524 |
|
|
* {@link #pollFirst(long,TimeUnit) pollFirst}. |
525 |
|
|
* |
526 |
jsr166 |
1.2 |
* @return the head of this deque, or {@code null} if the |
527 |
dl |
1.1 |
* specified waiting time elapses before an element is available |
528 |
|
|
* @throws InterruptedException if interrupted while waiting |
529 |
|
|
*/ |
530 |
|
|
E poll(long timeout, TimeUnit unit) |
531 |
|
|
throws InterruptedException; |
532 |
|
|
|
533 |
|
|
/** |
534 |
|
|
* Retrieves, but does not remove, the head of the queue represented by |
535 |
|
|
* this deque (in other words, the first element of this deque). |
536 |
|
|
* This method differs from {@link #peek peek} only in that it throws an |
537 |
|
|
* exception if this deque is empty. |
538 |
|
|
* |
539 |
|
|
* <p>This method is equivalent to {@link #getFirst() getFirst}. |
540 |
|
|
* |
541 |
|
|
* @return the head of this deque |
542 |
|
|
* @throws NoSuchElementException if this deque is empty |
543 |
|
|
*/ |
544 |
|
|
E element(); |
545 |
|
|
|
546 |
|
|
/** |
547 |
|
|
* Retrieves, but does not remove, the head of the queue represented by |
548 |
|
|
* this deque (in other words, the first element of this deque), or |
549 |
jsr166 |
1.2 |
* returns {@code null} if this deque is empty. |
550 |
dl |
1.1 |
* |
551 |
|
|
* <p>This method is equivalent to {@link #peekFirst() peekFirst}. |
552 |
|
|
* |
553 |
jsr166 |
1.2 |
* @return the head of this deque, or {@code null} if this deque is empty |
554 |
dl |
1.1 |
*/ |
555 |
|
|
E peek(); |
556 |
|
|
|
557 |
|
|
/** |
558 |
|
|
* Removes the first occurrence of the specified element from this deque. |
559 |
|
|
* If the deque does not contain the element, it is unchanged. |
560 |
jsr166 |
1.2 |
* More formally, removes the first element {@code e} such that |
561 |
|
|
* {@code o.equals(e)} (if such an element exists). |
562 |
|
|
* Returns {@code true} if this deque contained the specified element |
563 |
dl |
1.1 |
* (or equivalently, if this deque changed as a result of the call). |
564 |
|
|
* |
565 |
|
|
* <p>This method is equivalent to |
566 |
|
|
* {@link #removeFirstOccurrence(Object) removeFirstOccurrence}. |
567 |
|
|
* |
568 |
|
|
* @param o element to be removed from this deque, if present |
569 |
jsr166 |
1.2 |
* @return {@code true} if this deque changed as a result of the call |
570 |
dl |
1.1 |
* @throws ClassCastException if the class of the specified element |
571 |
|
|
* is incompatible with this deque |
572 |
|
|
* (<a href="../Collection.html#optional-restrictions">optional</a>) |
573 |
|
|
* @throws NullPointerException if the specified element is null |
574 |
|
|
* (<a href="../Collection.html#optional-restrictions">optional</a>) |
575 |
|
|
*/ |
576 |
|
|
boolean remove(Object o); |
577 |
|
|
|
578 |
|
|
/** |
579 |
jsr166 |
1.2 |
* Returns {@code true} if this deque contains the specified element. |
580 |
|
|
* More formally, returns {@code true} if and only if this deque contains |
581 |
|
|
* at least one element {@code e} such that {@code o.equals(e)}. |
582 |
dl |
1.1 |
* |
583 |
|
|
* @param o object to be checked for containment in this deque |
584 |
jsr166 |
1.2 |
* @return {@code true} if this deque contains the specified element |
585 |
dl |
1.1 |
* @throws ClassCastException if the class of the specified element |
586 |
|
|
* is incompatible with this deque |
587 |
|
|
* (<a href="../Collection.html#optional-restrictions">optional</a>) |
588 |
|
|
* @throws NullPointerException if the specified element is null |
589 |
|
|
* (<a href="../Collection.html#optional-restrictions">optional</a>) |
590 |
|
|
*/ |
591 |
|
|
public boolean contains(Object o); |
592 |
|
|
|
593 |
|
|
/** |
594 |
|
|
* Returns the number of elements in this deque. |
595 |
|
|
* |
596 |
|
|
* @return the number of elements in this deque |
597 |
|
|
*/ |
598 |
|
|
public int size(); |
599 |
|
|
|
600 |
|
|
/** |
601 |
|
|
* Returns an iterator over the elements in this deque in proper sequence. |
602 |
|
|
* The elements will be returned in order from first (head) to last (tail). |
603 |
|
|
* |
604 |
|
|
* @return an iterator over the elements in this deque in proper sequence |
605 |
|
|
*/ |
606 |
|
|
Iterator<E> iterator(); |
607 |
|
|
|
608 |
|
|
// *** Stack methods *** |
609 |
|
|
|
610 |
|
|
/** |
611 |
jsr166 |
1.3 |
* Pushes an element onto the stack represented by this deque (in other |
612 |
|
|
* words, at the head of this deque) if it is possible to do so |
613 |
|
|
* immediately without violating capacity restrictions, throwing an |
614 |
|
|
* {@code IllegalStateException} if no space is currently available. |
615 |
dl |
1.1 |
* |
616 |
|
|
* <p>This method is equivalent to {@link #addFirst(Object) addFirst}. |
617 |
|
|
* |
618 |
|
|
* @throws IllegalStateException {@inheritDoc} |
619 |
|
|
* @throws ClassCastException {@inheritDoc} |
620 |
|
|
* @throws NullPointerException if the specified element is null |
621 |
|
|
* @throws IllegalArgumentException {@inheritDoc} |
622 |
|
|
*/ |
623 |
|
|
void push(E e); |
624 |
|
|
} |