Writing a program with 2 threads which prints alternatively

Question

I got asked this question recently in an interview.

Write a program with two threads (A and B), where A prints 1 , B prints 2 and so on until 50 is r

Answer 1

May be this is still relevant:

public class MyRunnable implements Runnable {
    public static int counter = 0;
    public static int turn = 0;
    public static Object lock = new Object();

    @Override
    public void run() {
        while (counter < 50) {
            synchronized (lock) {
                if (turn == 0) {

                    System.out.println(counter + " from thread "
                            + Thread.currentThread().getName());
                    turn = 1;
                    try {
                        lock.wait();
                    } catch (InterruptedException e) {
                        Thread.currentThread().interrupt();
                    }
                } else {
                    turn = 0;
                    lock.notify();
                }

            }
        }
    }
}

and then the main function

public static void main(String[] args) {
        Thread threadA = new Thread(new MyRunnable());
        Thread threadB = new Thread(new MyRunnable ());
        threadA.start();
        threadB.start();
}