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Java > Open Source Codes > org > jboss > util > WaitSemaphore


1 /*
2   * JBoss, Home of Professional Open Source
3   * Copyright 2005, JBoss Inc., and individual contributors as indicated
4   * by the @authors tag. See the copyright.txt in the distribution for a
5   * full listing of individual contributors.
6   *
7   * This is free software; you can redistribute it and/or modify it
8   * under the terms of the GNU Lesser General Public License as
9   * published by the Free Software Foundation; either version 2.1 of
10   * the License, or (at your option) any later version.
11   *
12   * This software is distributed in the hope that it will be useful,
13   * but WITHOUT ANY WARRANTY; without even the implied warranty of
14   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15   * Lesser General Public License for more details.
16   *
17   * You should have received a copy of the GNU Lesser General Public
18   * License along with this software; if not, write to the Free
19   * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
20   * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
21   */
22 package org.jboss.util;
23
24 /**
25  * Wait exclusive semaphore with wait - notify primitives
26  *
27  * @author <a HREF="mailto:simone.bordet@compaq.com">Simone Bordet</a>
28  * @version $Revision: 1958 $
29  */
30 public class WaitSemaphore
31    extends Semaphore
32    implements WaitSync
33 {
34    // Constants -----------------------------------------------------
35 private final static int MAX_USERS_ALLOWED = 1;
36
37    // Attributes ----------------------------------------------------
38 private int m_waiters;
39
40    // Static --------------------------------------------------------
41
42    // Constructors --------------------------------------------------
43 public WaitSemaphore()
44    {
45       super(MAX_USERS_ALLOWED);
46    }
47
48    // Public --------------------------------------------------------
49 public void doWait() throws InterruptedException JavaDoc
50    {
51       synchronized (this)
52       {
53          release();
54          ++m_waiters;
55          waitImpl(this);
56          --m_waiters;
57          acquire();
58       }
59    }
60
61    public void doNotify() throws InterruptedException JavaDoc
62    {
63       synchronized (this)
64       {
65          if (getWaiters() > 0)
66          {
67             acquire();
68             notify();
69             release();
70          }
71       }
72    }
73
74    public int getWaiters()
75    {
76       synchronized (this)
77       {
78          return m_waiters;
79       }
80    }
81
82    // Object overrides ---------------------------------------------------
83 public String JavaDoc toString()
84    {
85       return super.toString() + " - " + m_waiters;
86    }
87
88    // Package protected ---------------------------------------------
89
90    // Protected -----------------------------------------------------
91
92    // Private -------------------------------------------------------
93
94    // Inner classes -------------------------------------------------
95 }
96
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