Thread Program four in Java

public class Thread_Demo extends Thread{

public void run(){
System.out.println("Some text");
}
public static void main(String[] args) throws InterruptedException{


Thread_Demo t=new Thread_Demo();
Thread_Demo td1=new Thread_Demo();

t.start();

System.out.println("ISALIVE :"+t.isAlive());
t.sleep(500);
System.out.println("ISALIVE :"+t.isAlive());
//t.destroy();
t.resume();
System.out.println("ISALIVE :"+t.isAlive());
}

}