//listing 6

// A simple example that uses an Executor.

import java.util.concurrent.*;

class SimpExec {

public static void main(String args[]) {

long start = System.currentTimeMillis();

CountDownLatch cdl1 = new CountDownLatch(500000);

CountDownLatch cdl2 = new CountDownLatch(500000);

CountDownLatch cdl3 = new CountDownLatch(500000);

CountDownLatch cdl4 = new CountDownLatch(500000);

ExecutorService es = Executors.newFixedThreadPool(4);

//ExecutorService es = Executors.newCachedThreadPool();

System.out.println("Starting");

// Start the threads.

es.execute(new MyThread(cdl1, "A"));

es.execute(new MyThread(cdl2, "B"));

es.execute(new MyThread(cdl3, "C"));

es.execute(new MyThread(cdl4, "D"));

try {

cdl1.await();

cdl2.await();

cdl3.await();

cdl4.await();

} catch (InterruptedException exc) {

System.out.println(exc);

}

if (!es.isTerminated())

es.shutdown();

System.out.println("Done");

long end = System.currentTimeMillis();

System.out.println(end-start);

}

}

class MyThread implements Runnable {

String name;

CountDownLatch latch;

MyThread(CountDownLatch c, String n) {

latch = c;

name = n;

new Thread(this);

}

public void run() {

for (int i = 0; i < 500000; i++) {

System.out.println(name + ": " + i);

latch.countDown();

}

}

}