Difference in thread execution in Java

See the execution of two similar programs in Java. One inherits from Thread and another implements the interface Runnable :

Program 1:

public class PingPong extends Thread{
private String msg;
private int delay;

PingPong(String s,int tempo){
    msg = s;
    delay = tempo;
}

public void run(){
    try{
        for (int i=1;i<=10;i++){
            System.out.println(msg+ " " + i);
            Thread.sleep(delay);
        }
    }
    catch (Exception e){
        System.err.println("Deu pau!");
        return;
    }
}

public static void main(String[] args) {
    PingPong ping = new PingPong("ping",500);
    ping.start();

    PingPong pong = new PingPong("pong",1000);
    pong.start();

    System.out.println("*** FIM DO PROGRAMA PRINCIPAL ***");
}}

It generates the following output:

Andwehaveprogram2:

publicclassPingPong2implementsRunnable{privateStringmsg;privateintdelay;PingPong2(Strings,inttempo){msg=s;delay=tempo;}publicvoidrun(){try{for(inti=1;i<=10;i++){System.out.println(msg+" " + i);
                Thread.sleep(delay);
            }
        }
        catch (Exception e){
            System.err.println("Deu pau!");
            return;
        }
    }

    public static void main(String[] args) {
        Runnable ping = new PingPong2("ping",500);
        Runnable pong = new PingPong2("pong",1000);

        new Thread(ping).start();
        new Thread(pong).start();
        System.out.println("*** FIM DO PROGRAMA PRINCIPAL ***");
    }
}  

Generating the following output:

Becausetheoutputinprogram1doesnotprint"ping1" because in the implementation of the run() method, on-screen printing is done before putting the thread to sleep )?