/*

Deadlock. Two threads, two locks on different objects in different order.

Thread 1 locks on 2 then 1, thread 2 locks on 1 then 2. In lock 1 assign to var a, in lock 2 assign to b.

Print a and b inside inner lock, and after inner lock.

See multiple states and some deadlocks.

Possible messages:

22 22 33 33

22 23 33 33

33 33 22 22

33 23 22 22

deadlock

*/

public class threads_37_deadlock {

public static void main(String[] args) {

Thread thread2 = new Thread(new MyRunnable2(2));

thread2.start();

Thread thread3 = new Thread(new MyRunnable3(3));

thread3.start();

try {

thread2.join();

thread3.join();

} catch (InterruptedException e) {

System.out.println(e);

}

System.out.println("Done!");

}

}

class MyRunnable2 implements Runnable {

static int a;

static int b;

static Object monitor1 = new Object();

static Object monitor2 = new Object();

int id;

MyRunnable2(int id) {

this.id = id;

}

public void run() {

synchronized(monitor1) {

a = id;

synchronized(monitor2) {

b = id;

System.out.println("Thread" + id + " inner lock: a = " + a + ", b = " + b);

}

System.out.println("Thread" + id + " outer lock: a = " + a + ", b = " + b);

}

}

}

class MyRunnable3 implements Runnable {

int id;

MyRunnable3(int id) {

this.id = id;

}

public void run() {

synchronized(MyRunnable2.monitor2) {

MyRunnable2.b = id;

synchronized(MyRunnable2.monitor1) {

MyRunnable2.a = id;

System.out.println("Thread" + id + " inner lock: a = " + MyRunnable2.a + ", b = " + MyRunnable2.b);

}

System.out.println("Thread" + id + " outer lock: a = " + MyRunnable2.a + ", b = " + MyRunnable2.b);

}

}

}