Deadlocker.java

import java.util.concurrent.Semaphore;

public class Deadlocker {

    public static void main(String[] args) {
        new Thread(new Runnable() {
            public void run() {
                while (true) {
                    try {
                        one();
                        System.out.println("one");
                    } catch (InterruptedException e) {}
                }
            }
        }).start();
        new Thread(new Runnable() {
            public void run() {
                while (true) {
                    try {
                        two();
                        System.out.println("two");
                    } catch (InterruptedException e) {}
                }
            }
        }).start();
    }

    private static final Semaphore foo = new Semaphore(1);
    private static final Semaphore bar = new Semaphore(1);

    private static void one() throws InterruptedException {
        foo.acquire();
        bar.acquire();
        bar.release();
        foo.release();
    }

    private static void two() throws InterruptedException {
        bar.acquire();
        foo.acquire();
        foo.release();
        bar.release();
    }

}