TestBarrier.java

import java.io.*;

/**
 * A testing harness for the Barrier class.
 *
 * Proper output is that we should see is that all threads 
 * output an 'A' before reaching the barrier and then a 'B'
 * after proceeding through the barrier. Therefore, output
 * should appear as a series of 'A's followed by an equal count
 * of 'B's. (There should not be an intermingling of 'A's and 'B's.
 */

public class TestBarrier  
{
	public static final int THREAD_COUNT = 5;

        public static void main(String args[]) throws java.io.IOException {
		System.out.println("Proper output is that we should see is that all threads");
 		System.out.println("output an 'A' before reaching the barrier and then a 'B'");
 		System.out.println("after proceeding through the barrier. Therefore, output");
 		System.out.println("should appear as a series of 'A's followed by an equal count");
 		System.out.println("of 'B's. (There should not be an intermingling of 'A's and 'B's.");
		System.out.println("\n\nPress Enter to begin the test:");
		(new BufferedReader(new InputStreamReader(System.in))).read();

		// initialize the barrier to the number of threads
		// waiting upon the barrier
          Barrier barrier = new BarrierImpl(THREAD_COUNT);

		Thread[] workers = new Thread[THREAD_COUNT];
		for (int i = 0; i < workers.length; i++) { 
			workers[i] = new Thread(new Worker(barrier));
			workers[i].start();
		}

		try {
			for (int i = 0; i < workers.length; i++)
				workers[i].join();
		}
		catch (InterruptedException ie) { }

		System.out.println("\n\nPress Enter to begin the freeAll() test:");
          (new BufferedReader(new InputStreamReader(System.in))).read();
	
		barrier = new BarrierImpl(THREAD_COUNT + 1);
		workers = new Thread[THREAD_COUNT];
          for (int i = 0; i < workers.length; i++) {
               workers[i] = new Thread(new Worker(barrier));
               workers[i].start();
          }

		try {
			Thread.sleep(3000);
		}
		catch (InterruptedException ie) { }
		barrier.freeAll();

        }
}

/**
 * A worker using the Barrier
 */
class Worker implements Runnable 
{
	private Barrier partA;

	public Worker(Barrier partA) {
		this.partA = partA;
	}

	/**
	 * Each thread will do some work for awhile, and then
	 * invoke waitForOthers(). A thread may proceed when all
	 * other threads have arrived at the barrier.
	 */
	public void run() {
		System.out.println("A");
		SleepUtilities.nap();

		partA.waitForOthers();

		System.out.println("B");
	}
}