Trying to learn about threads

Question

Hi guys,
I'm trying to learn more about threads......i've written a small program for a better understand, but i don't understand the order of the output i'm getting:
public class testme {
public static void main(String[] args) {
Theshape mover = new Theshape("go");
     mover.start();
System.out.println ("checkpoint 1");
System.out.println ("checkpoint 2");
     }//main
}//class testme
class Theshape extends Thread {
public int count;
public String thego;
Theshape (String gg){
     thego= gg;
count=0;
}//constructor
public void run(){
try {
do{
System.out.println (thego);
sleep(1000);
System.out.println ("johnny");
count=count+1;
}while(count<8);
} catch (InterruptedException e) {}
}//run          
}//class theshape
........the output i get is:
checkpoint 1
checkpoint 2
go
johnny
go
johnny
go
johnny
go
johnny
go
johnny
go
johnny
go
johnny
go
johnny
I would like to know why "checkpoint 1" and "checkpoint 2" is printed first, even though the call to the run method is made before the two statements. i would have thought that the two checkpoint statements would be printed last.
Can anyone help?
Thanks,
Zaf

Answer 1

After you've issued the 'mover.start()' call, a new thread pops into existence. The first thread (your main thread) continues to run while the second thread prepares itself to start up. On your machine, this startup takes a (little) while, so your main thread is able to print those two line just before the other thread is able to print something. That's all there is to it. If you put a 'Thread.sleep(1234)' between those two println statements in your main thread, the output would probably be a bit different. Give it a try.
kind regards,
Jos