| /* |
| * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| * |
| * This code is free software; you can redistribute it and/or modify it |
| * under the terms of the GNU General Public License version 2 only, as |
| * published by the Free Software Foundation. Oracle designates this |
| * particular file as subject to the "Classpath" exception as provided |
| * by Oracle in the LICENSE file that accompanied this code. |
| * |
| * This code is distributed in the hope that it will be useful, but WITHOUT |
| * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| * version 2 for more details (a copy is included in the LICENSE file that |
| * accompanied this code). |
| * |
| * You should have received a copy of the GNU General Public License version |
| * 2 along with this work; if not, write to the Free Software Foundation, |
| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| * |
| * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
| * or visit www.oracle.com if you need additional information or have any |
| * questions. |
| */ |
| |
| /* |
| * This file is available under and governed by the GNU General Public |
| * License version 2 only, as published by the Free Software Foundation. |
| * However, the following notice accompanied the original version of this |
| * file: |
| * |
| * Written by Doug Lea with assistance from members of JCP JSR-166 |
| * Expert Group and released to the public domain, as explained at |
| * http://creativecommons.org/publicdomain/zero/1.0/ |
| */ |
| |
| |
| package java.util.concurrent; |
| |
| |
| /** |
| * A synchronization aid that allows one or more threads to wait until |
| * a set of operations being performed in other threads completes. |
| * |
| * <p>A {@code CountDownLatch} is initialized with a given <em>count</em>. |
| * The {@link #await await} methods block until the current count reaches |
| * zero due to invocations of the {@link #countDown} method, after which |
| * all waiting threads are released and any subsequent invocations of |
| * {@link #await await} return immediately. This is a one-shot phenomenon |
| * -- the count cannot be reset. If you need a version that resets the |
| * count, consider using a {@link java.util.concurrent.CyclicBarrier CyclicBarrier}. |
| * |
| * <p>A {@code CountDownLatch} is a versatile synchronization tool |
| * and can be used for a number of purposes. A |
| * {@code CountDownLatch} initialized with a count of one serves as a |
| * simple on/off latch, or gate: all threads invoking {@link #await await} |
| * wait at the gate until it is opened by a thread invoking {@link |
| * #countDown}. A {@code CountDownLatch} initialized to <em>N</em> |
| * can be used to make one thread wait until <em>N</em> threads have |
| * completed some action, or some action has been completed N times. |
| * |
| * <p>A useful property of a {@code CountDownLatch} is that it |
| * doesn't require that threads calling {@code countDown} wait for |
| * the count to reach zero before proceeding, it simply prevents any |
| * thread from proceeding past an {@link #await await} until all |
| * threads could pass. |
| * |
| * <p><b>Sample usage:</b> Here is a pair of classes in which a group |
| * of worker threads use two countdown latches: |
| * <ul> |
| * <li>The first is a start signal that prevents any worker from proceeding |
| * until the driver is ready for them to proceed; |
| * <li>The second is a completion signal that allows the driver to wait |
| * until all workers have completed. |
| * </ul> |
| * |
| * <pre> {@code |
| * class Driver { // ... |
| * void main() throws InterruptedException { |
| * CountDownLatch startSignal = new CountDownLatch(1); |
| * CountDownLatch doneSignal = new CountDownLatch(N); |
| * |
| * for (int i = 0; i < N; ++i) // create and start threads |
| * new Thread(new Worker(startSignal, doneSignal)).start(); |
| * |
| * doSomethingElse(); // don't let run yet |
| * startSignal.countDown(); // let all threads proceed |
| * doSomethingElse(); |
| * doneSignal.await(); // wait for all to finish |
| * } |
| * } |
| * |
| * class Worker implements Runnable { |
| * private final CountDownLatch startSignal; |
| * private final CountDownLatch doneSignal; |
| * Worker(CountDownLatch startSignal, CountDownLatch doneSignal) { |
| * this.startSignal = startSignal; |
| * this.doneSignal = doneSignal; |
| * } |
| * public void run() { |
| * try { |
| * startSignal.await(); |
| * doWork(); |
| * doneSignal.countDown(); |
| * } catch (InterruptedException ex) {} // return; |
| * } |
| * |
| * void doWork() { ... } |
| * }}</pre> |
| * |
| * <p>Another typical usage would be to divide a problem into N parts, |
| * describe each part with a Runnable that executes that portion and |
| * counts down on the latch, and queue all the Runnables to an |
| * Executor. When all sub-parts are complete, the coordinating thread |
| * will be able to pass through await. (When threads must repeatedly |
| * count down in this way, instead use a {@link java.util.concurrent.CyclicBarrier CyclicBarrier}.) |
| * |
| * <pre> {@code |
| * class Driver2 { // ... |
| * void main() throws InterruptedException { |
| * CountDownLatch doneSignal = new CountDownLatch(N); |
| * Executor e = ... |
| * |
| * for (int i = 0; i < N; ++i) // create and start threads |
| * e.execute(new WorkerRunnable(doneSignal, i)); |
| * |
| * doneSignal.await(); // wait for all to finish |
| * } |
| * } |
| * |
| * class WorkerRunnable implements Runnable { |
| * private final CountDownLatch doneSignal; |
| * private final int i; |
| * WorkerRunnable(CountDownLatch doneSignal, int i) { |
| * this.doneSignal = doneSignal; |
| * this.i = i; |
| * } |
| * public void run() { |
| * try { |
| * doWork(i); |
| * doneSignal.countDown(); |
| * } catch (InterruptedException ex) {} // return; |
| * } |
| * |
| * void doWork() { ... } |
| * }}</pre> |
| * |
| * <p>Memory consistency effects: Until the count reaches |
| * zero, actions in a thread prior to calling |
| * {@code countDown()} |
| * <a href="package-summary.html#MemoryVisibility"><i>happen-before</i></a> |
| * actions following a successful return from a corresponding |
| * {@code await()} in another thread. |
| * |
| * @since 1.5 |
| * @author Doug Lea |
| */ |
| |
| @SuppressWarnings({"unchecked", "deprecation", "all"}) |
| public class CountDownLatch { |
| |
| /** |
| * Constructs a {@code CountDownLatch} initialized with the given count. |
| * |
| * @param count the number of times {@link #countDown} must be invoked |
| * before threads can pass through {@link #await} |
| * @throws java.lang.IllegalArgumentException if {@code count} is negative |
| */ |
| |
| public CountDownLatch(int count) { throw new RuntimeException("Stub!"); } |
| |
| /** |
| * Causes the current thread to wait until the latch has counted down to |
| * zero, unless the thread is {@linkplain java.lang.Thread#interrupt Thread#interrupt}. |
| * |
| * <p>If the current count is zero then this method returns immediately. |
| * |
| * <p>If the current count is greater than zero then the current |
| * thread becomes disabled for thread scheduling purposes and lies |
| * dormant until one of two things happen: |
| * <ul> |
| * <li>The count reaches zero due to invocations of the |
| * {@link #countDown} method; or |
| * <li>Some other thread {@linkplain java.lang.Thread#interrupt Thread#interrupt} |
| * the current thread. |
| * </ul> |
| * |
| * <p>If the current thread: |
| * <ul> |
| * <li>has its interrupted status set on entry to this method; or |
| * <li>is {@linkplain java.lang.Thread#interrupt Thread#interrupt} while waiting, |
| * </ul> |
| * then {@link java.lang.InterruptedException InterruptedException} is thrown and the current thread's |
| * interrupted status is cleared. |
| * |
| * @throws java.lang.InterruptedException if the current thread is interrupted |
| * while waiting |
| */ |
| |
| public void await() throws java.lang.InterruptedException { throw new RuntimeException("Stub!"); } |
| |
| /** |
| * Causes the current thread to wait until the latch has counted down to |
| * zero, unless the thread is {@linkplain java.lang.Thread#interrupt Thread#interrupt}, |
| * or the specified waiting time elapses. |
| * |
| * <p>If the current count is zero then this method returns immediately |
| * with the value {@code true}. |
| * |
| * <p>If the current count is greater than zero then the current |
| * thread becomes disabled for thread scheduling purposes and lies |
| * dormant until one of three things happen: |
| * <ul> |
| * <li>The count reaches zero due to invocations of the |
| * {@link #countDown} method; or |
| * <li>Some other thread {@linkplain java.lang.Thread#interrupt Thread#interrupt} |
| * the current thread; or |
| * <li>The specified waiting time elapses. |
| * </ul> |
| * |
| * <p>If the count reaches zero then the method returns with the |
| * value {@code true}. |
| * |
| * <p>If the current thread: |
| * <ul> |
| * <li>has its interrupted status set on entry to this method; or |
| * <li>is {@linkplain java.lang.Thread#interrupt Thread#interrupt} while waiting, |
| * </ul> |
| * then {@link java.lang.InterruptedException InterruptedException} is thrown and the current thread's |
| * interrupted status is cleared. |
| * |
| * <p>If the specified waiting time elapses then the value {@code false} |
| * is returned. If the time is less than or equal to zero, the method |
| * will not wait at all. |
| * |
| * @param timeout the maximum time to wait |
| * @param unit the time unit of the {@code timeout} argument |
| * @return {@code true} if the count reached zero and {@code false} |
| * if the waiting time elapsed before the count reached zero |
| * @throws java.lang.InterruptedException if the current thread is interrupted |
| * while waiting |
| */ |
| |
| public boolean await(long timeout, java.util.concurrent.TimeUnit unit) throws java.lang.InterruptedException { throw new RuntimeException("Stub!"); } |
| |
| /** |
| * Decrements the count of the latch, releasing all waiting threads if |
| * the count reaches zero. |
| * |
| * <p>If the current count is greater than zero then it is decremented. |
| * If the new count is zero then all waiting threads are re-enabled for |
| * thread scheduling purposes. |
| * |
| * <p>If the current count equals zero then nothing happens. |
| */ |
| |
| public void countDown() { throw new RuntimeException("Stub!"); } |
| |
| /** |
| * Returns the current count. |
| * |
| * <p>This method is typically used for debugging and testing purposes. |
| * |
| * @return the current count |
| */ |
| |
| public long getCount() { throw new RuntimeException("Stub!"); } |
| |
| /** |
| * Returns a string identifying this latch, as well as its state. |
| * The state, in brackets, includes the String {@code "Count ="} |
| * followed by the current count. |
| * |
| * @return a string identifying this latch, as well as its state |
| */ |
| |
| public java.lang.String toString() { throw new RuntimeException("Stub!"); } |
| } |
| |
