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Java example source code file (Suspend.java)

This example Java source code file (Suspend.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

failure, interruptedexception, runnable, runtimeexception, suspend, thread, threadgroup

The Suspend.java Java example source code

/*
 * Copyright (c) 1999, 2013, Oracle and/or its affiliates. All rights reserved.
 * 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.
 *
 * 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.
 */

/**
 * @test
 * @bug 4176355 7181748
 * @summary Suspending a ThreadGroup that contains the current thread has
 *          unpredictable results.
 */

public class Suspend implements Runnable {

    private static volatile int count = 0;
    private static final ThreadGroup group = new ThreadGroup("");
    private static final Thread first = new Thread(group, new Suspend());
    private static final Thread second = new Thread(group, new Suspend());

    public void run() {
        while (true) {
            try {
                Thread.sleep(100);
                if (Thread.currentThread() == first) {
                    if (second.isAlive()) {
                        group.suspend();
                    }
                } else {
                    count++;
                }
            } catch (InterruptedException e) {
            }
        }
    }

    public static void main(String[] args) throws Exception {
        // Launch two threads as part of the same thread group
        first.start();
        second.start();

        // Wait for the thread group suspend to be issued
        while (!first.isAlive() || !second.isAlive()) {
            Thread.sleep(100);
        }
        Thread.sleep(1000);
        // Suppose, the thread group is now suspended

        count = 0;
        Thread.sleep(1000);

        // Increment of the count indicates that the second thread is still running
        boolean failed = (count > 1);
        first.stop();
        second.stop();
        if (failed) {
            throw new RuntimeException("Failure.");
        }
    }
}

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