resourceuser.java

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/**
 *  
 *  Concurrency utilities (JSR-166) example
 **/
package semaphore;

import java.net.*;
import java.io.*;
import java.util.concurrent.*;

/**
 *  Use resources from a pool and return them at random times
 **/
public class ResourceUser implements Runnable {
  private ResourcePool pool;
  private int threadId;
  private int runCount;
  private long hold;
  private long pause;

  /**
   *  Constructor
   *
   * @param pool The pool to get the resource from
   * @param threadId The id number of this thread
   * @param runCount The number of times to run the test loop
   * @param hold How long to hold the resource before releasing it
   * @param pause How long to wait before trying to re-aquire the resource
   **/
  public ResourceUser(ResourcePool pool, int threadId, int runCount,
      long hold, long pause) {
    this.pool = pool;
    this.threadId = threadId;
    this.runCount = runCount;
    this.hold = hold;
    this.pause = pause;
  }

  /**
   *  Request a resource from the pool and 
   *  return them after a random time period
   **/
  public void run() {
    for (int i = 0; i < runCount; i++) {
      try {
        /*  Get the resource from the pool  */
        System.out.println("[" + threadId + "] trying to get resource");
        Integer resource = pool.getResource();
        System.out.println("[" + threadId + "] aquired resource");

        Thread.sleep(hold);
        System.out.println("[" + threadId + "] releasing resource");
        pool.putResource(resource);
        Thread.sleep(pause);
      } catch (InterruptedException ie) {
        //  Silently ignore
      }
    }
  }

  /**
   *  Main entry point
   *
   * @param args The command line arguments
   **/
  public static void main(String[] args) {
    /*  Create a resource pool with two resources in it  */
    ResourcePool pool = new ResourcePool(2);

    /*  Use the Executors utility class to get a new FixedThreadPool.
     */
    ExecutorService threadExecutor = Executors.newFixedThreadPool(3);

    /*  Create three new resource users and start them using the previously
     *  initialised thread pool
     */
    ResourceUser r1 = new ResourceUser(pool, 1, 5, 400, 500);
    ResourceUser r2 = new ResourceUser(pool, 2, 5, 400, 500);
    ResourceUser r3 = new ResourceUser(pool, 3, 5, 400, 500);
    threadExecutor.execute(r1);
    threadExecutor.execute(r2);
    threadExecutor.execute(r3);

    /*  Clean up the thread pool so the program terminates cleanly  */
    threadExecutor.shutdown();
  }
}