VolatileTest.java

/**
 * @author <a href="mailto:l.weinan@gmail.com">Weinan Li</a>
 */
public class Lock {
    volatile boolean waiting = true;

    public void test() {
        new Thread(new Runnable() {
            public void run() {
                while (waiting) ;
                System.out.println("Thread 1 finished.");
            }
        }).start();

        new Thread(new Runnable() {
            public void run() {
                // Sleep for a bit so that thread 1 has a chance to start
                try {
                    Thread.sleep(100);
                } catch (InterruptedException ignored) {
                }
                System.out.println("Thread 2 shutdown...");
                waiting = false;
            }
        }).start();
    }

    public static void main(String[] args) {
        new Lock().test();
    }
}

---

import java.util.concurrent.CountDownLatch;

/**
 * @author <a href="mailto:l.weinan@gmail.com">Weinan Li</a>
 */
public class Volatile {
    volatile boolean waiting = true;
    CountDownLatch lock = new CountDownLatch(1);

    public void test() {
        new Thread(new Runnable() {
            public void run() {
                try {
                    lock.await();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                System.out.println("Thread 1 finished.");
            }
        }).start();

        new Thread(new Runnable() {
            public void run() {
                // Sleep for a bit so that thread 1 has a chance to start
                try {
                    Thread.sleep(100);
                } catch (InterruptedException ignored) {
                }
                System.out.println("Thread 2 shutdown...");
                lock.countDown();
            }
        }).start();
    }

    public static void main(String[] args) {
        new Volatile().test();
    }
}