Karel the robot

l got this error message when trying to start karel program:

Code:

---

Exception in thread "main" java.lang.NullPointerException
        at acm.program.Program.main(Program.java:917)
        at stanford.karel.Karel.main(Karel.java:202)

---

Code:

---

CODE:
import stanford.karel.*;


public class CollectNewspaperKarel extends SuperKarel {

        public void run() {
                  move();
                  turnRight();
                  move();
                  turnLeft();
                  move();
                  pickBeeper();
        }

}

---