650 lines
29 KiB
Java
650 lines
29 KiB
Java
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/*
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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/*
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* This file is available under and governed by the GNU General Public
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* License version 2 only, as published by the Free Software Foundation.
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* However, the following notice accompanied the original version of this
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* file:
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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.Deque;
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import java.util.Iterator;
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import java.util.NoSuchElementException;
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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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* <p>{@code BlockingDeque} methods come in four forms, with different ways
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* 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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* {@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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* <table class="plain">
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* <caption>Summary of BlockingDeque methods</caption>
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* <tr>
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* <th id="First" colspan="5"> First Element (Head)</th>
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* </tr>
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* <tr>
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* <td></td>
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* <th id="FThrow" style="font-weight:normal; font-style: italic">Throws exception</th>
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* <th id="FValue" style="font-weight:normal; font-style: italic">Special value</th>
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* <th id="FBlock" style="font-weight:normal; font-style: italic">Blocks</th>
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* <th id="FTimes" style="font-weight:normal; font-style: italic">Times out</th>
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* </tr>
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* <tr>
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* <th id="FInsert" style="text-align:left">Insert</th>
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* <td headers="First FInsert FThrow">{@link #addFirst(Object) addFirst(e)}</td>
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* <td headers="First FInsert FValue">{@link #offerFirst(Object) offerFirst(e)}</td>
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* <td headers="First FInsert FBlock">{@link #putFirst(Object) putFirst(e)}</td>
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* <td headers="First FInsert FTimes">{@link #offerFirst(Object, long, TimeUnit) offerFirst(e, time, unit)}</td>
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* </tr>
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* <tr>
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* <th id="FRemove" style="text-align:left">Remove</th>
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* <td headers="First FRemove FThrow">{@link #removeFirst() removeFirst()}</td>
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* <td headers="First FRemove FValue">{@link #pollFirst() pollFirst()}</td>
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* <td headers="First FRemove FBlock">{@link #takeFirst() takeFirst()}</td>
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* <td headers="First FRemove FTimes">{@link #pollFirst(long, TimeUnit) pollFirst(time, unit)}</td>
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* </tr>
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* <tr>
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* <th id="FExamine" style="text-align:left">Examine</th>
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* <td headers="First FExamine FThrow">{@link #getFirst() getFirst()}</td>
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* <td headers="First FExamine FValue">{@link #peekFirst() peekFirst()}</td>
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* <td headers="First FExamine FBlock" style="font-style:italic">not applicable</td>
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* <td headers="First FExamine FTimes" style="font-style:italic">not applicable</td>
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* </tr>
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* <tr>
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* <th id="Last" colspan="5"> Last Element (Tail)</th>
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* </tr>
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* <tr>
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* <td></td>
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* <th id="LThrow" style="font-weight:normal; font-style: italic">Throws exception</th>
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* <th id="LValue" style="font-weight:normal; font-style: italic">Special value</th>
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* <th id="LBlock" style="font-weight:normal; font-style: italic">Blocks</th>
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* <th id="LTimes" style="font-weight:normal; font-style: italic">Times out</th>
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* </tr>
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* <tr>
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* <th id="LInsert" style="text-align:left">Insert</th>
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* <td headers="Last LInsert LThrow">{@link #addLast(Object) addLast(e)}</td>
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* <td headers="Last LInsert LValue">{@link #offerLast(Object) offerLast(e)}</td>
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* <td headers="Last LInsert LBlock">{@link #putLast(Object) putLast(e)}</td>
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* <td headers="Last LInsert LTimes">{@link #offerLast(Object, long, TimeUnit) offerLast(e, time, unit)}</td>
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* </tr>
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* <tr>
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* <th id="LRemove" style="text-align:left">Remove</th>
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* <td headers="Last LRemove LThrow">{@link #removeLast() removeLast()}</td>
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* <td headers="Last LRemove LValue">{@link #pollLast() pollLast()}</td>
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* <td headers="Last LRemove LBlock">{@link #takeLast() takeLast()}</td>
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* <td headers="Last LRemove LTimes">{@link #pollLast(long, TimeUnit) pollLast(time, unit)}</td>
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* </tr>
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* <tr>
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* <th id="LExamine" style="text-align:left">Examine</th>
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* <td headers="Last LExamine LThrow">{@link #getLast() getLast()}</td>
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* <td headers="Last LExamine LValue">{@link #peekLast() peekLast()}</td>
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* <td headers="Last LExamine LBlock" style="font-style:italic">not applicable</td>
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* <td headers="Last LExamine LTimes" style="font-style:italic">not applicable</td>
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* </tr>
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* </table>
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*
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* <p>Like any {@link BlockingQueue}, a {@code BlockingDeque} is thread safe,
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* 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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* <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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*
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* <table class="plain">
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* <caption>Comparison of BlockingQueue and BlockingDeque methods</caption>
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* <tr>
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* <td></td>
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* <th id="BQueue"> {@code BlockingQueue} Method</th>
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* <th id="BDeque"> Equivalent {@code BlockingDeque} Method</th>
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* </tr>
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* <tr>
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* <th id="Insert" rowspan="4" style="text-align:left; vertical-align:top">Insert</th>
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* <th id="add" style="font-weight:normal; text-align:left">{@link #add(Object) add(e)}</th>
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* <td headers="Insert BDeque add">{@link #addLast(Object) addLast(e)}</td>
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* </tr>
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* <tr>
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* <th id="offer1" style="font-weight:normal; text-align:left">{@link #offer(Object) offer(e)}</th>
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* <td headers="Insert BDeque offer1">{@link #offerLast(Object) offerLast(e)}</td>
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* </tr>
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* <tr>
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* <th id="put" style="font-weight:normal; text-align:left">{@link #put(Object) put(e)}</th>
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* <td headers="Insert BDeque put">{@link #putLast(Object) putLast(e)}</td>
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* </tr>
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* <tr>
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* <th id="offer2" style="font-weight:normal; text-align:left">{@link #offer(Object, long, TimeUnit) offer(e, time, unit)}</th>
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* <td headers="Insert BDeque offer2">{@link #offerLast(Object, long, TimeUnit) offerLast(e, time, unit)}</td>
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* </tr>
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* <tr>
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* <th id="Remove" rowspan="4" style="text-align:left; vertical-align:top">Remove</th>
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* <th id="remove" style="font-weight:normal; text-align:left">{@link #remove() remove()}</th>
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* <td headers="Remove BDeque remove">{@link #removeFirst() removeFirst()}</td>
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* </tr>
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* <tr>
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* <th id="poll1" style="font-weight:normal; text-align:left">{@link #poll() poll()}</th>
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* <td headers="Remove BDeque poll1">{@link #pollFirst() pollFirst()}</td>
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* </tr>
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* <tr>
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* <th id="take" style="font-weight:normal; text-align:left">{@link #take() take()}</th>
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* <td headers="Remove BDeque take">{@link #takeFirst() takeFirst()}</td>
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* </tr>
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* <tr>
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* <th id="poll2" style="font-weight:normal; text-align:left">{@link #poll(long, TimeUnit) poll(time, unit)}</th>
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* <td headers="Remove BDeque poll2">{@link #pollFirst(long, TimeUnit) pollFirst(time, unit)}</td>
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* </tr>
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* <tr>
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* <th id="Examine" rowspan="2" style="text-align:left; vertical-align:top">Examine</th>
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* <th id="element" style="font-weight:normal; text-align:left">{@link #element() element()}</th>
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* <td headers="Examine BDeque element">{@link #getFirst() getFirst()}</td>
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* </tr>
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* <tr>
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* <th id="peek" style="font-weight:normal; text-align:left">{@link #peek() peek()}</th>
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* <td headers="Examine BDeque peek">{@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}/java.base/java/util/package-summary.html#CollectionsFramework">
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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 deque
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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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* throwing an {@code IllegalStateException} if no space is currently
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* 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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* throwing an {@code IllegalStateException} if no space is currently
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* 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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* returning {@code true} upon success and {@code false} if no space is
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* 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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* returning {@code true} upon success and {@code false} if no space is
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* 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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* {@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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* 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
|
||
|
|
* @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);
|
||
|
|
}
|