Threads

[MannY Gates]

There are two threads. Can anyone explain what's happening? The threads are executed in a manner that only after one thread is completely executed the next thread is executed and not interchanging the execution.

public class MyThread implements Runnable {
     private String str = "This is ";
      private int[] array = {1,2,3,4,5,6,7,8,9,10};
  
     public static void main(String args[]) {
       MyThread z = new MyThread();
       (new Thread(z)).start();
        (new Thread(z)).start();
     }
 
     public  void  run() {
       for(int w = 0;w < 10;w++) {
         System.out.println(str +  array[w] + ".");
       }
     }
   }

Output is:

This is 1.
This is 2.
This is 3.
This is 4.
This is 5.
This is 6.
This is 7.
This is 8.
This is 9.
This is 10.
This is 1.
This is 2.
This is 3.
This is 4.
This is 5.
This is 6.
This is 7.
This is 8.
This is 9.
This is 10.

[Barry Gaunt]

Why should the threads interchange their orders of execution?

[MannY Gates]

hmmm, but I guess when you increase the array elements which I did... One thred should not dominate the cpu time. They should share the cpu as both have equal priority.

[Barry Gaunt]

Possibly, but why should they?

[MannY Gates]

You have a point Barry... This means we can't possibly predict the output it can be anything right? What if such questions come on certifications?

[Barry Gaunt]

That option is usually among the choices. Now try to find out what you can do to force the execution to interchange amongst the threads.

[Barry Gaunt]

MannY? You sleepin?

[MannY Gates]

Oh Sorry barry... I got your point...

[Barry Gaunt]

Um... oh never mind.

[MannY Gates]

Hey Barry please check my private message.

[Jeroen Wenting]

Originally posted by MannY Gates:
You have a point Barry... This means we can't possibly predict the output it can be anything right? What if such questions come on certifications?

You can indeed not predict the order of execution.
Make the loops longer.
When they get to a few hundred cycles you'll start to see them alternating in a seemingly random manner.

On your machine and JVM the Thread scheduler just didn't swap out the first thread before it completed. On a slower machine it may well do so.

[MannY Gates]

Yes I agree with you Jeroen.
Thanks for pitching in.