feat(jdk8): move files to new folder to avoid resources compiled.
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376
jdkSrc/jdk8/java/util/concurrent/BlockingQueue.java
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376
jdkSrc/jdk8/java/util/concurrent/BlockingQueue.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.Collection;
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import java.util.Queue;
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/**
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* A {@link java.util.Queue} that additionally supports operations
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* that wait for the queue to become non-empty when retrieving an
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* element, and wait for space to become available in the queue when
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* storing an element.
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*
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* <p>{@code BlockingQueue} 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 BORDER CELLPADDING=3 CELLSPACING=1>
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* <caption>Summary of BlockingQueue methods</caption>
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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 #add add(e)}</td>
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* <td>{@link #offer offer(e)}</td>
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* <td>{@link #put put(e)}</td>
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* <td>{@link #offer(Object, long, TimeUnit) offer(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 #remove remove()}</td>
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* <td>{@link #poll poll()}</td>
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* <td>{@link #take take()}</td>
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* <td>{@link #poll(long, TimeUnit) poll(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 #element element()}</td>
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* <td>{@link #peek peek()}</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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* <p>A {@code BlockingQueue} does not accept {@code null} elements.
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* Implementations throw {@code NullPointerException} on attempts
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* to {@code add}, {@code put} or {@code offer} a {@code null}. A
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* {@code null} is used as a sentinel value to indicate failure of
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* {@code poll} operations.
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*
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* <p>A {@code BlockingQueue} may be capacity bounded. At any given
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* time it may have a {@code remainingCapacity} beyond which no
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* additional elements can be {@code put} without blocking.
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* A {@code BlockingQueue} without any intrinsic capacity constraints always
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* reports a remaining capacity of {@code Integer.MAX_VALUE}.
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*
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* <p>{@code BlockingQueue} implementations are designed to be used
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* primarily for producer-consumer queues, but additionally support
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* the {@link java.util.Collection} interface. So, for example, it is
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* possible to remove an arbitrary element from a queue using
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* {@code remove(x)}. However, such operations are in general
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* <em>not</em> performed very efficiently, and are intended for only
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* occasional use, such as when a queued message is cancelled.
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*
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* <p>{@code BlockingQueue} implementations are thread-safe. All
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* queuing methods achieve their effects atomically using internal
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* locks or other forms of concurrency control. However, the
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* <em>bulk</em> Collection operations {@code addAll},
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* {@code containsAll}, {@code retainAll} and {@code removeAll} are
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* <em>not</em> necessarily performed atomically unless specified
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* otherwise in an implementation. So it is possible, for example, for
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* {@code addAll(c)} to fail (throwing an exception) after adding
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* only some of the elements in {@code c}.
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*
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* <p>A {@code BlockingQueue} does <em>not</em> intrinsically support
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* any kind of "close" or "shutdown" operation to
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* indicate that no more items will be added. The needs and usage of
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* such features tend to be implementation-dependent. For example, a
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* common tactic is for producers to insert special
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* <em>end-of-stream</em> or <em>poison</em> objects, that are
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* interpreted accordingly when taken by consumers.
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*
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* <p>
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* Usage example, based on a typical producer-consumer scenario.
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* Note that a {@code BlockingQueue} can safely be used with multiple
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* producers and multiple consumers.
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* <pre> {@code
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* class Producer implements Runnable {
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* private final BlockingQueue queue;
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* Producer(BlockingQueue q) { queue = q; }
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* public void run() {
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* try {
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* while (true) { queue.put(produce()); }
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* } catch (InterruptedException ex) { ... handle ...}
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* }
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* Object produce() { ... }
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* }
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*
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* class Consumer implements Runnable {
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* private final BlockingQueue queue;
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* Consumer(BlockingQueue q) { queue = q; }
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* public void run() {
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* try {
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* while (true) { consume(queue.take()); }
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* } catch (InterruptedException ex) { ... handle ...}
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* }
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* void consume(Object x) { ... }
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* }
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*
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* class Setup {
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* void main() {
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* BlockingQueue q = new SomeQueueImplementation();
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* Producer p = new Producer(q);
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* Consumer c1 = new Consumer(q);
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* Consumer c2 = new Consumer(q);
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* new Thread(p).start();
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* new Thread(c1).start();
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* new Thread(c2).start();
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* }
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* }}</pre>
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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 BlockingQueue}
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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 BlockingQueue} 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 1.5
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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 BlockingQueue<E> extends Queue<E> {
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/**
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* Inserts the specified element into this queue if it is possible to do
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* so immediately without violating capacity restrictions, returning
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* {@code true} upon success and throwing an
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* {@code IllegalStateException} if no space is currently available.
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* When using a capacity-restricted queue, it is generally preferable to
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* use {@link #offer(Object) offer}.
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*
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* @param e the element to add
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* @return {@code true} (as specified by {@link Collection#add})
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* @throws IllegalStateException if the element cannot be added at this
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* time due to capacity restrictions
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* @throws ClassCastException if the class of the specified element
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* prevents it from being added to this queue
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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 queue
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*/
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boolean add(E e);
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/**
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* Inserts the specified element into this queue if it is possible to do
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* so immediately without violating capacity restrictions, returning
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* {@code true} upon success and {@code false} if no space is currently
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* available. When using a capacity-restricted queue, this method is
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* generally preferable to {@link #add}, which can fail to insert an
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* element only by throwing an exception.
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*
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* @param e the element to add
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* @return {@code true} if the element was added to this queue, else
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* {@code false}
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* @throws ClassCastException if the class of the specified element
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* prevents it from being added to this queue
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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 queue
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*/
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boolean offer(E e);
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/**
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* Inserts the specified element into this queue, waiting if necessary
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* 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 queue
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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 queue
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*/
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void put(E e) throws InterruptedException;
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/**
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* Inserts the specified element into this queue, waiting up to the
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* specified wait time 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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* @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 queue
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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 queue
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*/
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boolean offer(E e, long timeout, TimeUnit unit)
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throws InterruptedException;
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/**
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* Retrieves and removes the head of this queue, waiting if necessary
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* until an element becomes available.
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*
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* @return the head of this queue
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* @throws InterruptedException if interrupted while waiting
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*/
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E take() throws InterruptedException;
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/**
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* Retrieves and removes the head of this queue, waiting up to the
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* specified wait time if necessary for an element to 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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* {@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 queue, or {@code null} if the
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* specified 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 poll(long timeout, TimeUnit unit)
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throws InterruptedException;
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/**
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* Returns the number of additional elements that this queue can ideally
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* (in the absence of memory or resource constraints) accept without
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* blocking, or {@code Integer.MAX_VALUE} if there is no intrinsic
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* limit.
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*
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* <p>Note that you <em>cannot</em> always tell if an attempt to insert
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* an element will succeed by inspecting {@code remainingCapacity}
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* because it may be the case that another thread is about to
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* insert or remove an element.
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*
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* @return the remaining capacity
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*/
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int remainingCapacity();
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/**
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* Removes a single instance of the specified element from this queue,
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* if it is present. More formally, removes an element {@code e} such
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* that {@code o.equals(e)}, if this queue contains one or more such
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* elements.
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* Returns {@code true} if this queue contained the specified element
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* (or equivalently, if this queue changed as a result of the call).
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*
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* @param o element to be removed from this queue, if present
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* @return {@code true} if this queue changed as a result of the call
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* @throws ClassCastException if the class of the specified element
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* is incompatible with this queue
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* (<a href="../Collection.html#optional-restrictions">optional</a>)
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* @throws NullPointerException if the specified element is null
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* (<a href="../Collection.html#optional-restrictions">optional</a>)
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*/
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boolean remove(Object o);
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/**
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* Returns {@code true} if this queue contains the specified element.
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* More formally, returns {@code true} if and only if this queue contains
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* at least one element {@code e} such that {@code o.equals(e)}.
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*
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* @param o object to be checked for containment in this queue
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* @return {@code true} if this queue contains the specified element
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* @throws ClassCastException if the class of the specified element
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* is incompatible with this queue
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* (<a href="../Collection.html#optional-restrictions">optional</a>)
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* @throws NullPointerException if the specified element is null
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* (<a href="../Collection.html#optional-restrictions">optional</a>)
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*/
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public boolean contains(Object o);
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/**
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* Removes all available elements from this queue and adds them
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* to the given collection. This operation may be more
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* efficient than repeatedly polling this queue. A failure
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* encountered while attempting to add elements to
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* collection {@code c} may result in elements being in neither,
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* either or both collections when the associated exception is
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* thrown. Attempts to drain a queue to itself result in
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* {@code IllegalArgumentException}. Further, the behavior of
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* this operation is undefined if the specified collection is
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* modified while the operation is in progress.
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*
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* @param c the collection to transfer elements into
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* @return the number of elements transferred
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* @throws UnsupportedOperationException if addition of elements
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* is not supported by the specified collection
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* @throws ClassCastException if the class of an element of this queue
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* prevents it from being added to the specified collection
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* @throws NullPointerException if the specified collection is null
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* @throws IllegalArgumentException if the specified collection is this
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* queue, or some property of an element of this queue prevents
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* it from being added to the specified collection
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*/
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int drainTo(Collection<? super E> c);
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/**
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* Removes at most the given number of available elements from
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* this queue and adds them to the given collection. A failure
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* encountered while attempting to add elements to
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* collection {@code c} may result in elements being in neither,
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* either or both collections when the associated exception is
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* thrown. Attempts to drain a queue to itself result in
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* {@code IllegalArgumentException}. Further, the behavior of
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* this operation is undefined if the specified collection is
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* modified while the operation is in progress.
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*
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* @param c the collection to transfer elements into
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* @param maxElements the maximum number of elements to transfer
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* @return the number of elements transferred
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* @throws UnsupportedOperationException if addition of elements
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* is not supported by the specified collection
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* @throws ClassCastException if the class of an element of this queue
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* prevents it from being added to the specified collection
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* @throws NullPointerException if the specified collection is null
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* @throws IllegalArgumentException if the specified collection is this
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* queue, or some property of an element of this queue prevents
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* it from being added to the specified collection
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*/
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int drainTo(Collection<? super E> c, int maxElements);
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}
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Block a user