gistfile1.txt

class test1 implements Runnable {
  long start;
  long stop;
  static long sum = 0;
  static Object lock;
  
  public test1(long start, long stop, AtomicLong sum) {
    this.start = start;
    this.stop = stop;
    this.sum = sum;
  }

  public void run() {
    synchronize(lock) {
      for(int i = start; i < stop; i++) {
        sum += i;
      }
    }
  }

  public static void main(String[] args) throws Exception {
    Thread t1 = new Thread(new test1(0,5000));
    Thread t2 = new Thread(new test1(5001,10000));
    t1.start();
    t2.start();
    t1.join();
    t2.join();
    System.out.println(sum);
  }
}