public class Count2000 implements Runnable {
  static int count = 0;
  public static void main(String[] args) {
    Count2000 me = new Count2000();
    me.startTwoThreads();
  } 
  private void startTwoThreads() {
    Thread firstThread = new Thread(this);
    Thread secondThread = new Thread(this);
    firstThread.start();
    secondThread.start();
  }
  // add 1 to a static, shared variable (named count) 1000 times
  private void countUp() {
    for(int i = 0; i < 1000; i++) {
      // With the next line uncommented, the final total will be 2000
      // With it commented, the final total is usually much smaller, and
      //   it can even be *less* than the count shown by the 
      //   FIRST terminating thread
      // Note the program runs slower when synchronized

      //synchronized(this)
      {
        int x = count;
        try {
          // simulate computing a result (0 to 2 ms)
          Thread.sleep((int)(Math.random() * 3));
        } catch ( InterruptedException e ) {
          // it would be *very* surprising if the exception were thrown...
          e.printStackTrace();
        }
        count = x + 1;
        // the following also creates bad counts, but only on multi-core systems
        //   and the error amount is much smaller
        //count += 1;
      }
    }
  }
  public void run() {
    System.out.println("Running a thread.");
    countUp();
    // display result when thread terminates
    System.out.println("Thread terminating with count = " + count);
  }
}