CountDownLatchDemo.java

package com.codecafe.concurrency.countdownlatch;

import java.util.concurrent.CountDownLatch;

public class CountDownLatchDemo {

  public static void main(String[] args) throws InterruptedException {
    // Let us create task that is going to
    // wait for four threads before it starts
    CountDownLatch latch = new CountDownLatch(4);

    // Create 4 worker threads and start them
    Thread worker1 = new Thread(new Task(1000, latch), "WORKER-1");
    Thread worker2 = new Thread(new Task(2000, latch), "WORKER-2");
    Thread worker3 = new Thread(new Task(3000, latch), "WORKER-3");
    Thread worker4 = new Thread(new Task(4000, latch), "WORKER-4");

    worker1.start();
    worker2.start();
    worker3.start();
    worker4.start();

    // The main task waits for four threads
    latch.await();

    // Main thread has started
    System.out.println(Thread.currentThread().getName() + " has finished");
  }

}