public class Main implements Runnable {

  public static int a, b;

​

  public static void main(String[] args) {

    a = 100;

    b = 100;

​

    // Check the total amount shared between a and b before the transfers

    System.out.println("Total before: " + (a + b));

​

    // Run threads which will transfer amounts between a and b

    Thread thread1 = new Thread(new Main());

    Thread thread2 = new Thread(new Main());

    thread1.start();

    thread2.start();

​

    // Wait for the threads to finish running

    try {

      thread1.join();

      thread2.join();

    } catch (InterruptedException e) {

      e.printStackTrace();

    }

​

    // Check the total amount shared between a and b after the transfers

    // It should be the same amount as before

    System.out.println("Total after: " + (a + b));

  }

​

  public void run() {

    for (int i = 0; i < 10000000; i++) {

      transfer();

    }

  }

​

  public static synchronized void transfer() {

    // Choose a random amount to transfer

    int amount = (int) (5.0 * Math.random());

​

    // Transfer between a and b

    if (a > b) {

      a -= amount;

      b += amount;

    } else {

      a += amount;

      b -= amount;

    }