Application.java

public class Application 
{
    public static void main(String[] args) throws Exception 
    {        
        System.out.println(" main thread has started ");
        CountDownLatch countDownLatch = new CountDownLatch(4);

        WorkerThread workerThread1 = new WorkerThread("thread1", countDownLatch);
        WorkerThread workerThread2 = new WorkerThread("thread2", countDownLatch);
        WorkerThread workerThread3 = new WorkerThread("thread3", countDownLatch);
        WorkerThread workerThread4 = new WorkerThread("thread4", countDownLatch);

        new Thread(workerThread1).start();
        new Thread(workerThread2).start();
        new Thread(workerThread3).start();
        new Thread(workerThread4).start();

        System.out.println(" all the worker threads have been started. next calling await() method ");
        countDownLatch.await();

        System.out.println(" Resume the main thread after executing all worker threads");
    }
}