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1   /*
2    * Copyright (c) 2000, 2001, Oracle and/or its affiliates. All rights reserved.
3    * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4    *
5    * This code is free software; you can redistribute it and/or modify it
6    * under the terms of the GNU General Public License version 2 only, as
7    * published by the Free Software Foundation.
8    *
9    * This code is distributed in the hope that it will be useful, but WITHOUT
10   * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11   * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
12   * version 2 for more details (a copy is included in the LICENSE file that
13   * accompanied this code).
14   *
15   * You should have received a copy of the GNU General Public License version
16   * 2 along with this work; if not, write to the Free Software Foundation,
17   * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18   *
19   * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20   * or visit www.oracle.com if you need additional information or have any
21   * questions.
22   *
23   */
24  
25  package sun.jvm.hotspot.utilities;
26  
27  /** This class abstracts the notion of a worker thread which is fed
28      tasks in the form of Runnables. */
29  
30  public class WorkerThread {
31    private volatile boolean done = false;
32    private MessageQueueBackend mqb;
33    private MessageQueue mq;
34  
35    public WorkerThread() {
36      mqb = new MessageQueueBackend();
37      mq = mqb.getFirstQueue();
38      new Thread(new MainLoop()).start();
39    }
40  
41    /** Runs the given Runnable in the thread represented by this
42        WorkerThread object at an unspecified later time. */
43    public void invokeLater(Runnable runnable) {
44      mq.writeMessage(runnable);
45    }
46  
47    /** Can be used to dispose of the internal worker thread. Note that
48        this method may return before the internal worker thread
49        terminates. */
50    public void shutdown() {
51      done = true;
52      mq.writeMessage(new Runnable() { public void run() {} });
53    }
54  
55    class MainLoop implements Runnable {
56      private MessageQueue myMq;
57  
58      public MainLoop() {
59        myMq = mqb.getSecondQueue();
60      }
61  
62      public void run() {
63        while (!done) {
64          Runnable runnable = (Runnable) myMq.readMessage();
65          try {
66            runnable.run();
67          } catch (Exception e) {
68            e.printStackTrace();
69          }
70        }
71      }
72    }
73  }