86 lines
2.7 KiB
Java
86 lines
2.7 KiB
Java
/*
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* Copyright (c) 2004, Oracle and/or its affiliates. All rights reserved.
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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.
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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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*
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* @summary Thiseclass is used to synchronize execution off two threads.
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* @author Swamy Venkataramanappa
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*/
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import java.util.concurrent.Semaphore;
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public class ThreadExecutionSynchronizer {
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private boolean waiting;
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private Semaphore semaphore;
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public ThreadExecutionSynchronizer() {
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semaphore = new Semaphore(1);
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waiting = false;
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}
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// Synchronizes two threads execution points.
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// Basically any thread could get scheduled to run and
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// it is not possible to know which thread reaches expected
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// execution point. So whichever thread reaches a execution
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// point first wait for the second thread. When the second thread
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// reaches the expected execution point will wake up
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// the thread which is waiting here.
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void stopOrGo() {
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semaphore.acquireUninterruptibly(); // Thread can get blocked.
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if (!waiting) {
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waiting = true;
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// Wait for second thread to enter this method.
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while(!semaphore.hasQueuedThreads()) {
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try {
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Thread.sleep(20);
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} catch (InterruptedException xx) {}
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}
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semaphore.release();
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} else {
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waiting = false;
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semaphore.release();
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}
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}
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// Wrapper function just for code readability.
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void waitForSignal() {
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stopOrGo();
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goSleep(50);
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}
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void signal() {
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stopOrGo();
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goSleep(50);
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}
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private static void goSleep(long ms) {
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try {
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Thread.sleep(ms);
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} catch (InterruptedException e) {
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e.printStackTrace();
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System.out.println("Unexpected exception.");
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}
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}
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}
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