Dan's thread question

[Veena Pointi]

class A extends Thread {
  private C c1;
  public A(String s1, C c1) {super(s1); this.c1 = c1;}
  public void run() {
    for (int i = 0; i < 3; i++) {
      System.out.print(currentThread().getName() + c1.getI());
    }
  }
}
class C {
  private int i;
  public synchronized int getI() {
    int oldValue = i;
    Thread.yield();
    i += 1;
    return oldValue;
  }
  public static void main (String[] args) {
    C c = new C();
    Thread t1 = new A("X", c);
    Thread t2 = new A("Y", c);
    t1.start();
    t2.start();
  }
}

Possible o/p
Prints: X0Y1X2Y3X4Y5. Prints: X0X1X2Y3Y4Y5
From the o/p it is clear that X & Y are taking turn even when getI() method is synchronized.Does Thread.yield() method inside getI() causes to give up lock ,held by thread X?
Thanks
Veena

[Alex Stojan]

Hello,
Since the yield() method moves the currently running thread to the Ready state I don't think the thread releases the lock. My understanding is that the threads X and Y are taking turns simply because they are two threads running at the same time. Since the getI() method is synchronized after one thread completes it the other thread might get hold of the C object and enter the getI() method. I think the yield() method does not affect the order of Xs and Ys, and I think that any order is possible here.
Thanks,
Alex Stojan