public abstract class SomeClass implements Runnable {

private Object lock = new Object ();

public void lock () {

synchronized (lock) {

try {

System.out.print ( "1");

lock.wait ();

} Catch (InterruptedException e) { }

}

}

public void unlock () {

synchronized (lock) {

lock.notify ();

System.out.print ( "2");

}

}

public static void main (String s []) {

new Thread (new SomeClass () {

public void run () {

lock ();

}

}). Start ();

new Thread (new SomeClass () {

public void run () {

unlock ();

}

}). Start ();

}

}

(Java)