Java example source code file (PreserveDispatchThread.java)

This example Java source code file (PreserveDispatchThread.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

awt, componentadapter, event, exception, failed, frame, interruptedexception, object, override, preservedispatchthread, runnable, runtimeexception, testdialog, testeventqueue

The PreserveDispatchThread.java Java example source code

/*
 * Copyright (c) 2010, 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 6424157
  @author Artem Ananiev: area=eventqueue
  @run main PreserveDispatchThread
*/

import java.awt.*;
import java.awt.event.*;

public class PreserveDispatchThread {

    private static volatile Frame f;
    private static volatile Dialog d;

    private static volatile boolean isEDT = true;

    public static void main(String[] args) throws Exception {
        f = new Frame("F");
        f.setSize(320, 340);
        f.setLocationRelativeTo(null);
        f.setVisible(true);

        try {
            test1();
            if (!isEDT) {
                throw new RuntimeException("Test FAILED (test1): event dispatch thread is changed");
            }

            test2();
            if (!isEDT) {
                throw new RuntimeException("Test FAILED (test2): event dispatch thread is changed");
            }

            test3();
            if (!isEDT) {
                throw new RuntimeException("Test FAILED (test3): event dispatch thread is changed");
            }
        } finally {
            if (d != null) {
                d.dispose();
            }
            f.dispose();
        }
    }

    /*
     * Tests that push/pop doesn't change the dispatch thread if
     * called on EDT.
     */
    private static void test1() throws Exception {
        EventQueue.invokeAndWait(new Runnable() {
            @Override
            public void run() {
                TestEventQueue teq = new TestEventQueue();
                EventQueue seq = Toolkit.getDefaultToolkit().getSystemEventQueue();
                try {
                    seq.push(teq);
                    d = new TestDialog();
                    d.setVisible(true);
                    checkEDT();
                } finally {
                    teq.pop();
                }
                checkEDT();
            }
        });
    }

    /*
     * Tests that push/pop doesn't change the dispatch thread if
     * called on the main thread.
     */
    private static void test2() throws Exception {
        TestEventQueue teq = new TestEventQueue();
        EventQueue seq = Toolkit.getDefaultToolkit().getSystemEventQueue();
        try {
            seq.push(teq);
            EventQueue.invokeAndWait(new Runnable() {
                @Override
                public void run() {
                    checkEDT();
                    d = new TestDialog();
                    d.setVisible(true);
                    checkEDT();
                }
            });
        } finally {
            teq.pop();
        }
    }

    private static final Object test3Lock = new Object();
    private static boolean test3Sync = false;

    /*
     * A complex test: several nested invokeLater() are called and
     * in every runnable a check for EDT is performed. At the ent
     * of the test we wait for all the runnables to be processed
     * and the dialog is disposed; otherwise the last EDT check can
     * be later than this method returns and the whole test is passed.
     */
    private static void test3() throws Exception {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                d = new Dialog(f, true);
                d.setSize(240, 180);
                d.setLocationRelativeTo(f);
                EventQueue.invokeLater(new Runnable() {
                    @Override
                    public void run() {
                        d.setVisible(true);
                        checkEDT();
                    }
                });
                EventQueue.invokeLater(new Runnable() {
                    @Override
                    public void run() {
                        TestEventQueue teq = new TestEventQueue();
                        EventQueue seq = Toolkit.getDefaultToolkit().getSystemEventQueue();
                        try {
                            seq.push(teq);
                            checkEDT();
                            EventQueue.invokeLater(new Runnable() {
                                @Override
                                public void run() {
                                    d.dispose();
                                    checkEDT();
                                    synchronized (test3Lock) {
                                        test3Sync = true;
                                        test3Lock.notify();
                                    }
                                }
                            });
                        } finally {
                            teq.pop();
                        }
                        checkEDT();
                    }
                });
                checkEDT();
            }
        });
        synchronized (test3Lock) {
            while (!test3Sync) {
                try {
                    test3Lock.wait();
                } catch (InterruptedException ie) {
                    break;
                }
            }
        }
        // Make sure all the nested invokeLater/invokeAndWait are processed
        EventQueue.invokeAndWait(new Runnable() {
            @Override
            public void run() {
            }
        });
    }

    private static void checkEDT() {
        isEDT = isEDT && EventQueue.isDispatchThread();
    }

    private static class TestEventQueue extends EventQueue {
        public TestEventQueue() {
            super();
        }
        public void pop() {
            super.pop();
        }
    }

    private static class TestDialog extends Dialog {
        private volatile boolean dialogShown = false;
        private volatile boolean paintCalled = false;
        public TestDialog() {
            super(f, true);
            setSize(240, 180);
            setLocationRelativeTo(f);
            addComponentListener(new ComponentAdapter() {
                @Override
                public void componentShown(ComponentEvent e) {
                    if (paintCalled) {
                        dispose();
                    }
                    dialogShown = true;
                }
            });
        }
        @Override
        public void paint(Graphics g) {
            if (dialogShown) {
                dispose();
            }
            paintCalled = true;
        }
    }

}