/*

Two threads, two locks on different objects, but not nested. No deadlocks.

Thread 1: lock 1, assign and print a, lock 2 - assign and print b.

Thread 2: lock 2, assign and print b, lock 1 - assign and print a.

See multiple states, but no deadlocks.

Message order: all permutations:

- 1 1 2 2

- 1 2 1 2

- 1 2 2 1

- 2 1 1 2

- 2 1 2 1

- 2 2 1 1

Since for each thread run the actual output may be very different, there are 38 solutions.

*/

public class threads_38_two_locks {

public static void main(String[] args) {

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

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

thread2.start();

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;

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

}

synchronized(monitor2) {

b = id;

System.out.println("Thread" + id + " inner 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;

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

}

synchronized(MyRunnable2.monitor1) {

MyRunnable2.a = id;

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

}

}

}