public class FirstThread extends Thread
{
    private int i;
    public void run(){
        for(;i<100 ; i++){
            System.out.println(getName()+" "+i);
        }
    }
    public static void main(String[] args){
        for(int i=0;i<100;i++){
            System.out.println(Thread.currentThread().getName()+" "+i);
            if(i==20){
                new FirstThread().start();
                new FirstThread().start();
            }
        }
    }
}