cs4003 - 2

DeadLock.java

class Monitor {
	String name;
	public volatile boolean locked = false;

	public Monitor(String name) {
		this.name = name;
	}

	public String getName() {
		return this.name;
	}

	public synchronized void ping(Monitor mon) {
		try {
			while (this.isLocked()) {
				wait();
			}
		} catch(InterruptedException e) {
			Thread.currentThread().interrupt();
		}

		System.out.println(this.name + " (ping): pinging " + mon.getName());
		mon.lock();
		System.out.println(this.name + " (ping): asking " + mon.getName() + " to confirm");
		mon.confirm(this);
		System.out.println(this.name + " (ping): got confirmation");

		mon.unlock();
		notifyAll();
	}

	public synchronized void confirm(Monitor mon) {
		System.out.println(this.name + " (confirm): confirm to " + mon.getName());
	}

	public synchronized void lock() {
		System.out.println(this.name + " (lock)");
		this.locked = true;
	}

	public synchronized void unlock() {
		System.out.println(this.name + " (unlock)");
		this.locked = false;
	}

	public boolean isLocked() {
		System.out.println(this.name + " (isLocked): " + this.locked);
		return this.locked;
	}
}


class Runner extends Thread {
	Monitor m1, m2;

	public Runner(Monitor m1, Monitor m2) {
		this.m1 = m1;
		this.m2 = m2;
	}

	public void run() {
		m1.ping(m2);
	}
}


public class DeadLock {
	public static void main(String args[]) {
		int i = 1;
		System.out.println("Starting..." + (i++));
		Monitor girl = new Monitor("Girl");
		Monitor boy = new Monitor("Boy");
		(new Runner(girl, boy)).start();
		(new Runner(boy, girl)).start();
	}
}