Some question on thread

Question

i think threads are unpredictable.say, the following code. some questions on the code.
public class Rpcraven{
     public static void main(String argv[]){
     Pmcraven pm1 = new Pmcraven("One");
     pm1.run(); // line1
     Pmcraven pm2 = new Pmcraven("Two");
     pm2.run();  // line 2
class Pmcraven extends Thread{
private String sTname="";
Pmcraven(String s){
     sTname = s;
public void run(){
     for(int i =0; i < 2 ; i++){
          try{
           sleep(1000);
          }catch(InterruptedException e){}
          yield();
          System.out.println(sTname);
}question 1 > note line 1 and line 2 . does this two threds are staarted at the same time ? or line 1 first and line 2 second as in the code ? this is very much important to me.
question 2 > ok, whoever goes first , now lets come to the try-catch block . there is sleep() who will sleep first ? so i need to know which thread is going to sleep first ? bcoz then i can say who will get the yield() method.
i find difficult to predict the output of this thred.
Output of One One Two Two.
one more thing, threads are always called by start() method ( run() is called implicitly) . here start() is not usued . still the code is working . how ?

Answer 1

question 1 > note line 1 and line 2 . does this two
threds are staarted at the same time ? or line 1 first
and line 2 second as in the code ? this is very much
important to me.If it's important, you are doing something wrong...
First, you shouldn't call the threads' run() method, that doesn't "start" the thread, it just calls run(). Use start() instead.
The threads are sort of started in order, but probably not in the way you think.
Think of it like this: there is a list of threads in the JVM. start() puts the thread in the list. After that, the CPU of your computer can run any thread in the list, for as long as it feels like. The CPU might run thread 1 for a few instructions, then thread 2 for a while, or it might start with thread 2, ... If you have a multi-CPU machine, the threads are run at the same time. It's unpredictable, except when you do explicit synhcronization or waiting.
question 2 > ok, whoever goes first , now lets come to
the try-catch block . there is sleep() who will sleep
first ? so i need to know which thread is going to
sleep first ?This is unpredictable. You can't know it. It will vary from run to run.
If you need two threads to do something in a predictable order, you'll need to do synchronization and waiting.
one more thing, threads are always called by start()
method ( run() is called implicitly) . here start()
is not usued . still the code is working . how ?You are not starting the threads, you are calling their run() methods sequentially.