Java Wait Nofify Example

waitnofify.java

import java.util.ArrayList;
import java.util.List;
import static java.lang.String.format;

public class NotifyTest {

	static final class NotifiableRunner extends Thread {

		private final int id;
		// The mutex upon which this thread will wait and respond to notify
		private final Lock lock;
		// Variable that determines whether the Thread should continue running
		private boolean keepalive = true;

		// Switch to false and the run() method will terminate

		public NotifiableRunner(int id, Lock lock) {
			super();
			this.id = id;
			this.lock = lock;
		}

		public void makewait() {
			synchronized (lock) {
				try {
					lock.wait();
				} catch (InterruptedException e) {
					e.printStackTrace();
				}
			}
		}

		@Override
		public void run() {
			while (isKeepalive()) {
				makewait();
				System.out.println(id);
			}
		}

		public boolean isKeepalive() {
			return keepalive;
		}

		public void setKeepalive(boolean keepalive) {
			this.keepalive = keepalive;
		}
	}

	private static final class Lock {
	}

	public static void main(String[] args) {
		final Lock lock = new Lock();

		List<NotifiableRunner> list = new ArrayList<NotifyTest.NotifiableRunner>();

		for (int i = 0; i < 4; i++) {
			System.err.println(format("creating %d", i));
			NotifiableRunner e = new NotifiableRunner(i, lock);
			e.start();
			list.add(e);
		}

		System.out.println("created threads");
		sleepytime(1000);
		System.out.println("notifying threads");

		notifyThreads(lock);
		sleepytime(1000);
		notifyThreads(lock);
		sleepytime(1000);

		System.out.println("finishing");
		terminateThreads(lock, list);

	}

	private static void terminateThreads(final Lock lock,
			List<NotifiableRunner> list) {
		for (NotifiableRunner nr : list) {
			nr.setKeepalive(false);
		}

		synchronized (lock) {
			lock.notifyAll();
		}
	}

	private static void notifyThreads(final Lock lock) {
		for (int i = 0; i < 4; i++) {
			synchronized (lock) {
				System.err.println(format("notifying %d", i));
				lock.notify();
			}
		}
	}

	private static void sleepytime(int millis) {
		try {
			Thread.sleep(millis);
		} catch (InterruptedException e) {
			e.printStackTrace();
		}
	}
}