creating a deadlock.

[mitti sharma]

I have to create a dead lock in the following code that has two worker threads that carry out the addition.
my assignment says it can be done by adding one line of code.
i was able to do it by changing the order of arguments(In w2 i changed it from s,a to a,s)

Worker w1 = new Worker (s,a);
Worker w2 = new Worker (a,s);

but as i said i have to add code line not alter the orignal one,so
can someone suggest me if there are other ways to put this in deadlock?

 
public static int sumArrays(int[] a1, int[] a2)
{
  int value = 0;
  int size = a1.length;
 
  if (size == a2.length) {
    // get lock on a1
    synchronized(a1) {
 
      Thread.yield();
      synchronized(a2) {
 
        for (int i=0; i<size; i++)
          value += a1[i] + a2[i];
      }
    }
  }
  return value;
}
 
}   

-----------------------------------------------------

  public class Worker extends Thread {
  int [] a1;
  int [] a2;
 
  public Worker (int [] a1, int [] a2) {
       this.a1 = a1;
       this.a2 = a2;
  }
 
  public void run() {
      ArraySumUtil.sumArrays(a1, a2);
 

  }
 
  public static void main (String [] args) {
      // set up some arrays
      int size = 100;
      int [] s = new int[size];
      int [] a = new int[size];
 
      for (int i=0; i< size; i++) {
          s[i] = i;
          a[i] = i*2;
      }
 

      // set up workers
      Worker w1 = new Worker (s,a);
      Worker w2 = new Worker (s,a);
 

      w1.start();
      w2.start();
 
      try {
          w1.join();
          w2.join();
      }
      catch (InterruptedException e) {}
 
      System.out.println("done.");
 

  }
 

}