ExecQueue


1   package org.sapia.ubik.rmi.server.command;
2   
3   import org.sapia.ubik.net.Timer;
4   import org.sapia.ubik.rmi.server.ShutdownException;
5   
6   import java.util.ArrayList  ;
7   import java.util.LinkedList  ;
8   import java.util.List  ;
9   
10  
11  /**
12   * Models a queue of <code>Executable</code> instances.
13   *
14   * @author Yanick Duchesne
15   * <dl>
16   * <dt><b>Copyright:</b><dd>Copyright &#169; 2002-2003 <a HREF="http://www.sapia-oss.org">Sapia Open Source Software</a>. All Rights Reserved.</dd></dt>
17   * <dt><b>License:</b><dd>Read the license.txt file of the jar or visit the
18   *        <a HREF="http://www.sapia-oss.org/license.html">license page</a> at the Sapia OSS web site</dd></dt>
19   * </dl>
20   */
21  public class ExecQueue {
22    private LinkedList   _queue    = new LinkedList  ();
23    private boolean    _shutdown;
24  
25    /**
26     * Constructor for CommandQueue.
27     */
28    public ExecQueue() {
29      super();
30    }
31  
32    /**
33     * Adds an <code>Executable</code> to this queue.
34     *
35     * @param toExecute an <code>Executable</code>.
36     */
37    public synchronized void add(Executable toExecute) {
38      if (_shutdown) {
39        throw new ShutdownException();
40      }
41  
42      _queue.add(toExecute);
43      notifyAll();
44    }
45  
46    /**
47     * Removes all the <code>Executable</code> from this queue and
48     * returns them; if the queue is empty, this method blocks until
49     * a new item is added.
50     *
51     * @return a <code>List</code> of <code>Executable</code>.
52     */
53    public synchronized List   removeAll()
54      throws InterruptedException  , ShutdownException {
55      while (_queue.size() == 0) {
56        if (_shutdown) {
57          notify();
58          throw new ShutdownException();
59        }
60  
61        wait();
62      }
63  
64      List   toReturn = new ArrayList  (_queue);
65      _queue.clear();
66  
67      return toReturn;
68    }
69  
70    /**
71     * Shuts down this instance.
72     *
73     * @param timeout a timeout in millis. If this queue still has pending
74     * objects after the timeout is reached, this method returns.
75     */
76    public synchronized void shutdown(long timeout) throws InterruptedException   {
77      _shutdown = true;
78      notifyAll();
79  
80      Timer timer = new Timer(timeout);
81  
82      while (_queue.size() > 0) {
83        wait(timeout);
84  
85        if (timer.isOver()) {
86          break;
87        }
88      }
89    }
90  
91    /**
92     * Returns this queue's size.
93     *
94     * @return this queue's size (the number of items in this queue).
95     */
96    public int size() {
97      return _queue.size();
98    }
99  
100   /**
101    * Removes the first <code>Executable</code> from this queue and returns it.
102    *
103    * @return an <code>Executable</code>.
104    */
105   public synchronized Executable remove()
106     throws InterruptedException  , ShutdownException {
107     while (_queue.size() == 0) {
108       if (_shutdown) {
109         notify();
110         throw new ShutdownException();
111       }
112 
113       wait();
114     }
115 
116     return (Executable) _queue.remove(0);
117   }
118 }
119
A to Z: JavaDoc & Examples Daily Java News & Articles Open Source Projects Open Source Codes Free Computer Books Remove Frame
Popular Tags