ThreadPool


1   /*
2    * Copyright (c) 2004, Rob Gordon.
3    */
4   package org.oddjob.util;
5   
6   
7   /**
8    * Very basic implementation of a thread pool.
9    * 
10   * @author Rob Gordon.
11   */
12  public class ThreadPool {
13  
14      private BlockingQueue queue = new BlockingQueue();
15      private boolean closed = true;
16  
17      private int poolSize = 3;
18      
19      
20      public void setPoolSize(int poolSize) {
21          this.poolSize = poolSize;
22      }
23      
24      public int getPoolSize() {
25          return poolSize;
26      }
27      
28      synchronized public void start() {
29          if (!closed) {
30              throw new IllegalStateException  ("Pool already started.");
31          }
32          closed = false;
33          for (int i = 0; i < poolSize; ++i) {
34              new PooledThread().start();
35          }
36      }
37  
38      synchronized public void execute(Runnable   job) {
39          if (closed) {
40              throw new PoolClosedException();
41          }
42          queue.enqueue(job);
43      }
44      
45      private class PooledThread extends Thread   {
46          
47          public void run() {
48              while (true) {
49                  Runnable   job = (Runnable  ) queue.dequeue();
50                  if (job == null) {
51                      break;
52                  }
53                  try {
54                      job.run();
55                  } catch (Throwable   t) {
56                      // ignore
57                  }
58              }
59          }
60      }
61  
62      public void close() {
63          closed = true;
64          queue.close();
65      }
66      
67      private static class PoolClosedException extends RuntimeException   {
68          PoolClosedException() { 
69              super ("Pool closed.");
70          }
71      }
72  }
73
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