I don't know about threads in Java. I like to know what is happening in this code because each time it runs, it produces a different output:

public class TwoThreadsDemo{
    public static void main(String[] args)
    {
        new SimpleThread("Java Programmer").start();
        new SimpleThread("Java Programmer").start();
    }
}

class SimpleThread extends Thread{
    public SimpleThread(String str)
    {
      super(str);
    }

    public void run()
    {
        for (int i=0;i<10;i++)
        {

           System.out.println(i + " " + getName());  

            try
            {
                sleep((long)(Math.random()*1000));
            }
            catch(InterruptedException e)
            {

            }

        }
        System.out.println("Done!" + getName());
    } 

}