BlockingQueue


1   /*
2    * Copyright � 2004, Rob Gordon.
3    */
4   package org.oddjob.util;
5   
6   import java.util.LinkedList  ;
7   
8   /**
9    *
10   * @author Rob Gordon.
11   */
12  public class BlockingQueue {
13  
14      private final LinkedList   list = new LinkedList  ();
15      private boolean closed = false;
16      private boolean wait = false;
17      
18      synchronized public void enqueue(Object   o) {
19          if (closed) {
20              throw new ClosedException();
21          }
22          list.add(o);
23          notify();
24      }
25  
26      synchronized public Object   dequeue() {
27          while (!closed && list.size() == 0) {
28              try {
29                  wait();
30              }
31              catch (InterruptedException   e) {
32                  // ignore
33              }
34          }
35          if (list.size() == 0) {
36              return null;
37          }
38          return list.removeFirst();
39      }
40      
41      synchronized public int size() {
42          return list.size();
43      }
44      
45      synchronized public void close() {
46          closed = true;
47          notifyAll();
48      }
49      
50      synchronized public void open() {
51          closed = false;
52      }
53      
54      public static class ClosedException extends RuntimeException   {
55          ClosedException() {
56              super("Queue closed.");
57          }
58      }
59  }
60

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