public class Counter implements Runnable {
     
  private int counter = 0;
  private final int rounds = 100000;
  
  public void run () {
    // try {
    for(int i = 0; i < rounds; i++) {
      synchronized(this) {counter++;}
    }
    // } catch (InterruptedException e) {
    // System.out.println ("Interrupted!");
    // }
  }
     
  public static void main (String[] args) {
    try {
      Counter c = new Counter ();
     
      // Create two threads that run our run () method.
      Thread t1 = new Thread (c, "thread1");
      Thread t2 = new Thread (c, "thread2");
     
      t1.start (); t2.start ();
     
      // Wait for the threads to finish.
      t1.join (); t2.join ();
     
      // Print the counter
      System.out.println(c.counter);
    } catch (InterruptedException e) {
      System.out.println ("Interrupted!");
    }
  }
}