1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/rt/emul/compact/src/main/java/java/util/concurrent/BlockingQueue.java Sat Mar 19 10:46:31 2016 +0100
1.3 @@ -0,0 +1,377 @@
1.4 +/*
1.5 + * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
1.6 + *
1.7 + * This code is free software; you can redistribute it and/or modify it
1.8 + * under the terms of the GNU General Public License version 2 only, as
1.9 + * published by the Free Software Foundation. Oracle designates this
1.10 + * particular file as subject to the "Classpath" exception as provided
1.11 + * by Oracle in the LICENSE file that accompanied this code.
1.12 + *
1.13 + * This code is distributed in the hope that it will be useful, but WITHOUT
1.14 + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
1.15 + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
1.16 + * version 2 for more details (a copy is included in the LICENSE file that
1.17 + * accompanied this code).
1.18 + *
1.19 + * You should have received a copy of the GNU General Public License version
1.20 + * 2 along with this work; if not, write to the Free Software Foundation,
1.21 + * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
1.22 + *
1.23 + * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
1.24 + * or visit www.oracle.com if you need additional information or have any
1.25 + * questions.
1.26 + */
1.27 +
1.28 +/*
1.29 + * This file is available under and governed by the GNU General Public
1.30 + * License version 2 only, as published by the Free Software Foundation.
1.31 + * However, the following notice accompanied the original version of this
1.32 + * file:
1.33 + *
1.34 + * Written by Doug Lea with assistance from members of JCP JSR-166
1.35 + * Expert Group and released to the public domain, as explained at
1.36 + * http://creativecommons.org/publicdomain/zero/1.0/
1.37 + */
1.38 +
1.39 +package java.util.concurrent;
1.40 +
1.41 +import java.util.Collection;
1.42 +import java.util.Queue;
1.43 +
1.44 +/**
1.45 + * A {@link java.util.Queue} that additionally supports operations
1.46 + * that wait for the queue to become non-empty when retrieving an
1.47 + * element, and wait for space to become available in the queue when
1.48 + * storing an element.
1.49 + *
1.50 + * <p><tt>BlockingQueue</tt> methods come in four forms, with different ways
1.51 + * of handling operations that cannot be satisfied immediately, but may be
1.52 + * satisfied at some point in the future:
1.53 + * one throws an exception, the second returns a special value (either
1.54 + * <tt>null</tt> or <tt>false</tt>, depending on the operation), the third
1.55 + * blocks the current thread indefinitely until the operation can succeed,
1.56 + * and the fourth blocks for only a given maximum time limit before giving
1.57 + * up. These methods are summarized in the following table:
1.58 + *
1.59 + * <p>
1.60 + * <table BORDER CELLPADDING=3 CELLSPACING=1>
1.61 + * <tr>
1.62 + * <td></td>
1.63 + * <td ALIGN=CENTER><em>Throws exception</em></td>
1.64 + * <td ALIGN=CENTER><em>Special value</em></td>
1.65 + * <td ALIGN=CENTER><em>Blocks</em></td>
1.66 + * <td ALIGN=CENTER><em>Times out</em></td>
1.67 + * </tr>
1.68 + * <tr>
1.69 + * <td><b>Insert</b></td>
1.70 + * <td>{@link #add add(e)}</td>
1.71 + * <td>{@link #offer offer(e)}</td>
1.72 + * <td>{@link #put put(e)}</td>
1.73 + * <td>{@link #offer(Object, long, TimeUnit) offer(e, time, unit)}</td>
1.74 + * </tr>
1.75 + * <tr>
1.76 + * <td><b>Remove</b></td>
1.77 + * <td>{@link #remove remove()}</td>
1.78 + * <td>{@link #poll poll()}</td>
1.79 + * <td>{@link #take take()}</td>
1.80 + * <td>{@link #poll(long, TimeUnit) poll(time, unit)}</td>
1.81 + * </tr>
1.82 + * <tr>
1.83 + * <td><b>Examine</b></td>
1.84 + * <td>{@link #element element()}</td>
1.85 + * <td>{@link #peek peek()}</td>
1.86 + * <td><em>not applicable</em></td>
1.87 + * <td><em>not applicable</em></td>
1.88 + * </tr>
1.89 + * </table>
1.90 + *
1.91 + * <p>A <tt>BlockingQueue</tt> does not accept <tt>null</tt> elements.
1.92 + * Implementations throw <tt>NullPointerException</tt> on attempts
1.93 + * to <tt>add</tt>, <tt>put</tt> or <tt>offer</tt> a <tt>null</tt>. A
1.94 + * <tt>null</tt> is used as a sentinel value to indicate failure of
1.95 + * <tt>poll</tt> operations.
1.96 + *
1.97 + * <p>A <tt>BlockingQueue</tt> may be capacity bounded. At any given
1.98 + * time it may have a <tt>remainingCapacity</tt> beyond which no
1.99 + * additional elements can be <tt>put</tt> without blocking.
1.100 + * A <tt>BlockingQueue</tt> without any intrinsic capacity constraints always
1.101 + * reports a remaining capacity of <tt>Integer.MAX_VALUE</tt>.
1.102 + *
1.103 + * <p> <tt>BlockingQueue</tt> implementations are designed to be used
1.104 + * primarily for producer-consumer queues, but additionally support
1.105 + * the {@link java.util.Collection} interface. So, for example, it is
1.106 + * possible to remove an arbitrary element from a queue using
1.107 + * <tt>remove(x)</tt>. However, such operations are in general
1.108 + * <em>not</em> performed very efficiently, and are intended for only
1.109 + * occasional use, such as when a queued message is cancelled.
1.110 + *
1.111 + * <p> <tt>BlockingQueue</tt> implementations are thread-safe. All
1.112 + * queuing methods achieve their effects atomically using internal
1.113 + * locks or other forms of concurrency control. However, the
1.114 + * <em>bulk</em> Collection operations <tt>addAll</tt>,
1.115 + * <tt>containsAll</tt>, <tt>retainAll</tt> and <tt>removeAll</tt> are
1.116 + * <em>not</em> necessarily performed atomically unless specified
1.117 + * otherwise in an implementation. So it is possible, for example, for
1.118 + * <tt>addAll(c)</tt> to fail (throwing an exception) after adding
1.119 + * only some of the elements in <tt>c</tt>.
1.120 + *
1.121 + * <p>A <tt>BlockingQueue</tt> does <em>not</em> intrinsically support
1.122 + * any kind of "close" or "shutdown" operation to
1.123 + * indicate that no more items will be added. The needs and usage of
1.124 + * such features tend to be implementation-dependent. For example, a
1.125 + * common tactic is for producers to insert special
1.126 + * <em>end-of-stream</em> or <em>poison</em> objects, that are
1.127 + * interpreted accordingly when taken by consumers.
1.128 + *
1.129 + * <p>
1.130 + * Usage example, based on a typical producer-consumer scenario.
1.131 + * Note that a <tt>BlockingQueue</tt> can safely be used with multiple
1.132 + * producers and multiple consumers.
1.133 + * <pre>
1.134 + * class Producer implements Runnable {
1.135 + * private final BlockingQueue queue;
1.136 + * Producer(BlockingQueue q) { queue = q; }
1.137 + * public void run() {
1.138 + * try {
1.139 + * while (true) { queue.put(produce()); }
1.140 + * } catch (InterruptedException ex) { ... handle ...}
1.141 + * }
1.142 + * Object produce() { ... }
1.143 + * }
1.144 + *
1.145 + * class Consumer implements Runnable {
1.146 + * private final BlockingQueue queue;
1.147 + * Consumer(BlockingQueue q) { queue = q; }
1.148 + * public void run() {
1.149 + * try {
1.150 + * while (true) { consume(queue.take()); }
1.151 + * } catch (InterruptedException ex) { ... handle ...}
1.152 + * }
1.153 + * void consume(Object x) { ... }
1.154 + * }
1.155 + *
1.156 + * class Setup {
1.157 + * void main() {
1.158 + * BlockingQueue q = new SomeQueueImplementation();
1.159 + * Producer p = new Producer(q);
1.160 + * Consumer c1 = new Consumer(q);
1.161 + * Consumer c2 = new Consumer(q);
1.162 + * new Thread(p).start();
1.163 + * new Thread(c1).start();
1.164 + * new Thread(c2).start();
1.165 + * }
1.166 + * }
1.167 + * </pre>
1.168 + *
1.169 + * <p>Memory consistency effects: As with other concurrent
1.170 + * collections, actions in a thread prior to placing an object into a
1.171 + * {@code BlockingQueue}
1.172 + * <a href="package-summary.html#MemoryVisibility"><i>happen-before</i></a>
1.173 + * actions subsequent to the access or removal of that element from
1.174 + * the {@code BlockingQueue} in another thread.
1.175 + *
1.176 + * <p>This interface is a member of the
1.177 + * <a href="{@docRoot}/../technotes/guides/collections/index.html">
1.178 + * Java Collections Framework</a>.
1.179 + *
1.180 + * @since 1.5
1.181 + * @author Doug Lea
1.182 + * @param <E> the type of elements held in this collection
1.183 + */
1.184 +public interface BlockingQueue<E> extends Queue<E> {
1.185 + /**
1.186 + * Inserts the specified element into this queue if it is possible to do
1.187 + * so immediately without violating capacity restrictions, returning
1.188 + * <tt>true</tt> upon success and throwing an
1.189 + * <tt>IllegalStateException</tt> if no space is currently available.
1.190 + * When using a capacity-restricted queue, it is generally preferable to
1.191 + * use {@link #offer(Object) offer}.
1.192 + *
1.193 + * @param e the element to add
1.194 + * @return <tt>true</tt> (as specified by {@link Collection#add})
1.195 + * @throws IllegalStateException if the element cannot be added at this
1.196 + * time due to capacity restrictions
1.197 + * @throws ClassCastException if the class of the specified element
1.198 + * prevents it from being added to this queue
1.199 + * @throws NullPointerException if the specified element is null
1.200 + * @throws IllegalArgumentException if some property of the specified
1.201 + * element prevents it from being added to this queue
1.202 + */
1.203 + boolean add(E e);
1.204 +
1.205 + /**
1.206 + * Inserts the specified element into this queue if it is possible to do
1.207 + * so immediately without violating capacity restrictions, returning
1.208 + * <tt>true</tt> upon success and <tt>false</tt> if no space is currently
1.209 + * available. When using a capacity-restricted queue, this method is
1.210 + * generally preferable to {@link #add}, which can fail to insert an
1.211 + * element only by throwing an exception.
1.212 + *
1.213 + * @param e the element to add
1.214 + * @return <tt>true</tt> if the element was added to this queue, else
1.215 + * <tt>false</tt>
1.216 + * @throws ClassCastException if the class of the specified element
1.217 + * prevents it from being added to this queue
1.218 + * @throws NullPointerException if the specified element is null
1.219 + * @throws IllegalArgumentException if some property of the specified
1.220 + * element prevents it from being added to this queue
1.221 + */
1.222 + boolean offer(E e);
1.223 +
1.224 + /**
1.225 + * Inserts the specified element into this queue, waiting if necessary
1.226 + * for space to become available.
1.227 + *
1.228 + * @param e the element to add
1.229 + * @throws InterruptedException if interrupted while waiting
1.230 + * @throws ClassCastException if the class of the specified element
1.231 + * prevents it from being added to this queue
1.232 + * @throws NullPointerException if the specified element is null
1.233 + * @throws IllegalArgumentException if some property of the specified
1.234 + * element prevents it from being added to this queue
1.235 + */
1.236 + void put(E e) throws InterruptedException;
1.237 +
1.238 + /**
1.239 + * Inserts the specified element into this queue, waiting up to the
1.240 + * specified wait time if necessary for space to become available.
1.241 + *
1.242 + * @param e the element to add
1.243 + * @param timeout how long to wait before giving up, in units of
1.244 + * <tt>unit</tt>
1.245 + * @param unit a <tt>TimeUnit</tt> determining how to interpret the
1.246 + * <tt>timeout</tt> parameter
1.247 + * @return <tt>true</tt> if successful, or <tt>false</tt> if
1.248 + * the specified waiting time elapses before space is available
1.249 + * @throws InterruptedException if interrupted while waiting
1.250 + * @throws ClassCastException if the class of the specified element
1.251 + * prevents it from being added to this queue
1.252 + * @throws NullPointerException if the specified element is null
1.253 + * @throws IllegalArgumentException if some property of the specified
1.254 + * element prevents it from being added to this queue
1.255 + */
1.256 + boolean offer(E e, long timeout, TimeUnit unit)
1.257 + throws InterruptedException;
1.258 +
1.259 + /**
1.260 + * Retrieves and removes the head of this queue, waiting if necessary
1.261 + * until an element becomes available.
1.262 + *
1.263 + * @return the head of this queue
1.264 + * @throws InterruptedException if interrupted while waiting
1.265 + */
1.266 + E take() throws InterruptedException;
1.267 +
1.268 + /**
1.269 + * Retrieves and removes the head of this queue, waiting up to the
1.270 + * specified wait time if necessary for an element to become available.
1.271 + *
1.272 + * @param timeout how long to wait before giving up, in units of
1.273 + * <tt>unit</tt>
1.274 + * @param unit a <tt>TimeUnit</tt> determining how to interpret the
1.275 + * <tt>timeout</tt> parameter
1.276 + * @return the head of this queue, or <tt>null</tt> if the
1.277 + * specified waiting time elapses before an element is available
1.278 + * @throws InterruptedException if interrupted while waiting
1.279 + */
1.280 + E poll(long timeout, TimeUnit unit)
1.281 + throws InterruptedException;
1.282 +
1.283 + /**
1.284 + * Returns the number of additional elements that this queue can ideally
1.285 + * (in the absence of memory or resource constraints) accept without
1.286 + * blocking, or <tt>Integer.MAX_VALUE</tt> if there is no intrinsic
1.287 + * limit.
1.288 + *
1.289 + * <p>Note that you <em>cannot</em> always tell if an attempt to insert
1.290 + * an element will succeed by inspecting <tt>remainingCapacity</tt>
1.291 + * because it may be the case that another thread is about to
1.292 + * insert or remove an element.
1.293 + *
1.294 + * @return the remaining capacity
1.295 + */
1.296 + int remainingCapacity();
1.297 +
1.298 + /**
1.299 + * Removes a single instance of the specified element from this queue,
1.300 + * if it is present. More formally, removes an element <tt>e</tt> such
1.301 + * that <tt>o.equals(e)</tt>, if this queue contains one or more such
1.302 + * elements.
1.303 + * Returns <tt>true</tt> if this queue contained the specified element
1.304 + * (or equivalently, if this queue changed as a result of the call).
1.305 + *
1.306 + * @param o element to be removed from this queue, if present
1.307 + * @return <tt>true</tt> if this queue changed as a result of the call
1.308 + * @throws ClassCastException if the class of the specified element
1.309 + * is incompatible with this queue
1.310 + * (<a href="../Collection.html#optional-restrictions">optional</a>)
1.311 + * @throws NullPointerException if the specified element is null
1.312 + * (<a href="../Collection.html#optional-restrictions">optional</a>)
1.313 + */
1.314 + boolean remove(Object o);
1.315 +
1.316 + /**
1.317 + * Returns <tt>true</tt> if this queue contains the specified element.
1.318 + * More formally, returns <tt>true</tt> if and only if this queue contains
1.319 + * at least one element <tt>e</tt> such that <tt>o.equals(e)</tt>.
1.320 + *
1.321 + * @param o object to be checked for containment in this queue
1.322 + * @return <tt>true</tt> if this queue contains the specified element
1.323 + * @throws ClassCastException if the class of the specified element
1.324 + * is incompatible with this queue
1.325 + * (<a href="../Collection.html#optional-restrictions">optional</a>)
1.326 + * @throws NullPointerException if the specified element is null
1.327 + * (<a href="../Collection.html#optional-restrictions">optional</a>)
1.328 + */
1.329 + public boolean contains(Object o);
1.330 +
1.331 + /**
1.332 + * Removes all available elements from this queue and adds them
1.333 + * to the given collection. This operation may be more
1.334 + * efficient than repeatedly polling this queue. A failure
1.335 + * encountered while attempting to add elements to
1.336 + * collection <tt>c</tt> may result in elements being in neither,
1.337 + * either or both collections when the associated exception is
1.338 + * thrown. Attempts to drain a queue to itself result in
1.339 + * <tt>IllegalArgumentException</tt>. Further, the behavior of
1.340 + * this operation is undefined if the specified collection is
1.341 + * modified while the operation is in progress.
1.342 + *
1.343 + * @param c the collection to transfer elements into
1.344 + * @return the number of elements transferred
1.345 + * @throws UnsupportedOperationException if addition of elements
1.346 + * is not supported by the specified collection
1.347 + * @throws ClassCastException if the class of an element of this queue
1.348 + * prevents it from being added to the specified collection
1.349 + * @throws NullPointerException if the specified collection is null
1.350 + * @throws IllegalArgumentException if the specified collection is this
1.351 + * queue, or some property of an element of this queue prevents
1.352 + * it from being added to the specified collection
1.353 + */
1.354 + int drainTo(Collection<? super E> c);
1.355 +
1.356 + /**
1.357 + * Removes at most the given number of available elements from
1.358 + * this queue and adds them to the given collection. A failure
1.359 + * encountered while attempting to add elements to
1.360 + * collection <tt>c</tt> may result in elements being in neither,
1.361 + * either or both collections when the associated exception is
1.362 + * thrown. Attempts to drain a queue to itself result in
1.363 + * <tt>IllegalArgumentException</tt>. Further, the behavior of
1.364 + * this operation is undefined if the specified collection is
1.365 + * modified while the operation is in progress.
1.366 + *
1.367 + * @param c the collection to transfer elements into
1.368 + * @param maxElements the maximum number of elements to transfer
1.369 + * @return the number of elements transferred
1.370 + * @throws UnsupportedOperationException if addition of elements
1.371 + * is not supported by the specified collection
1.372 + * @throws ClassCastException if the class of an element of this queue
1.373 + * prevents it from being added to the specified collection
1.374 + * @throws NullPointerException if the specified collection is null
1.375 + * @throws IllegalArgumentException if the specified collection is this
1.376 + * queue, or some property of an element of this queue prevents
1.377 + * it from being added to the specified collection
1.378 + */
1.379 + int drainTo(Collection<? super E> c, int maxElements);
1.380 +}