Context switching / Threads

Question

Hello !
The following program is for 3 Threads which do context switching.
Often we get '0' zero for the low priority thread when we run this program.
MY QUESTION IS WHY DO WE GET ZERO ?
As far as my understanding is concerned; even if preemptive multitasking is done by the threads,
the low priority thread should have run through few iterations and thus giving some value other
than zero '0'.
Secondly most of the time we get negative values for the high priority thread. Why is that ?
Is it because of the fact that volatile sets the variable 'running' to some different value ?
The speed of my processor is 1.5GHz.
GOD BLESS YOU.
NADEEM.
// Demonstrates threads priorities.
class Clicker implements Runnable {
  int click = 0;
  String name ;
  Thread t ;
  private boolean running = true ;
  public Clicker(String tname, int p) {
   name = tname ;
   t = new Thread(this, name);
   t.setPriority(p);
   System.out.println("Current Thread is " + t + " " + t.getPriority());
  public void start() {
   t.start();
  public void run() {
   while (running) {
    click++;
  public void stop() {
   running = false ;
class HLPriority {
public static void main(String args[]) {
   System.out.println("Active Count : " + Thread.activeCount());
   Thread.currentThread().setPriority(Thread.MAX_PRIORITY);
   Clicker hi = new Clicker("Hi", Thread.NORM_PRIORITY + 2);
   Clicker lo = new Clicker("Lo", Thread.NORM_PRIORITY - 2);
   System.out.println("Active Count : " + Thread.activeCount());
   lo.start();
   hi.start();
   try {
     System.out.println("Sleeping Thread : " + Thread.currentThread());
     Thread.sleep(10000);
   } catch (InterruptedException e) {
     System.out.println("Main Thread interrupted : " + e);
    hi.stop();
    lo.stop();
   try {
    hi.t.join();
    lo.t.join();
   } catch (InterruptedException e) {
     System.out.println("Interrupted Exception caught : " + e);
   System.out.println("Low priority thread  : " + lo.click);
   System.out.println("Hi  priority thread  : " + hi.click);
}

Answer 1

Hello !
The following program is for 3 Threads which do
context switching.
Often we get '0' zero for the low priority thread when
we run this program.
MY QUESTION IS WHY DO WE GET ZERO ?Presumably because the low priority thread gets no CPU time.
>
As far as my understanding is concerned; even if
preemptive multitasking is done by the threads,
the low priority thread should have run through few
iterations and thus giving some value other
than zero '0'.You can't make ANY assumptions about when or how much CPU time a given thread will get. Why don't you let your main thread sleep longer--a minute or 5 or ten--and see if LO gets some cycles then.
Secondly most of the time we get negative values for
the high priority thread. Why is that ?count = Integer.MAX_VALUE;
count++; // --> Integer.MIN_VALUE (-2^31)
I guess 10 seconds is enough time for a thread in a tight loop to count to 2 billion.
Is it because of the fact that volatile sets the
variable 'running' to some different value ?Volatile does nothing of the sort, and, in any case, isn't even in your code.
GOD BLESS YOU.I didn't sneeze.