Download UNIT1 – LCPS Karel example

Lab08
Hurdle Racing
Objective
Polymorphism. The if-else control structure.
Background
The hurdles shown below are all one-block tall hurdles. A beeper marks the finish line. An object of the
Racer class can traverse that race-course using the algorithm:
while(!arg.nextToABeeper())
if(arg.frontIsClear())
arg.move();
else
arg.jumpRight();
If there’s no hurdle, then move, otherwise jump over the hurdle. The else-clause jumpRight() is executed
when the condition frontIsClear() is false.
Now let's change the race-course so that instead of one-block tall
hurdles we must jump over hurdles of any height. We do not
change the algorithm above! The method arg.jumpRight() is a
perfectly good command—in the abstract—to jump hurdles of
any height. All we need to do is to write our own jumpRight().
In object-oriented programming we look around for a class that
does approximately what we want (i.e. Racer) and the extend it.
When we extend a class, we give the new class the powers that we really want—namely, how to jump
hurdles of different heights.
What about jumping hurdles of differing widths? Again, our original algorithm still works! All we have
to do is to write a new subclass that knows how to jump these new kinds of hurdles.
Racer
SteepleChaseRacer
BoxTopRacer
Each of the classes SteepleChaseRacer and BoxTopRacer will extend Racer and override jumpRight().
Specification
Consult the Unit 1 API for more information regarding the SteepleChaseRacer and BoxTopRacer classes.
Create Unit1\SteepleChaseRacer.java and Unit1\BoxTopRacer.java.
Implement
SteepleChaseRacer and BoxTopRacer classes as described above, then compile.
both
the
Load Unit1\Lab08.java. Compile and run. With maps “hurdle1”, “hurdle2”, and “hurdle3”, use an object
of type Racer. With maps “steeple1”, “steeple2”, and “steeple3”, use a SteepleChaseRacer object. With
maps “boxtop1”, “boxtop2”, and “boxtop3”, use a BoxTopRacer object.