Re: Understanding Classes

markspace <>
Tue, 21 Jul 2009 08:48:29 -0700
brian void wrote:

So would I just put all of the KarelJumps and KarelColor methods
inside SuperKarel? Do I just make one large object?

To answer literally, yes, your only recourse here is to make one big class.


Tomas Mikula had a good point, what you are doing seems to be just
adding methods to classes. Your classes for jumping and colors seem
over-kill. So there's one idea, if you are totally stuck on how to do
what you asked.

This doesn't seem like a "new" question, but if you're asking about
decomposing classes, Java does not have multiple inheritance. You
simulate multiple inheritance with composition and interfaces.

class Robot {
     ... has some methods

interface Jumping {
    ... more methods

interface Colors {
   ... more methods

class RobotJumping implements Jumping {
    ... implementation

class RobotColors implements Colors {
   ... implementation

class Karel extends Robot implements Jumping, Colors {

   private Jumping jump = new RobotJumping();
   private Colors colors = new RobotColors();

   ... implement Jumping and Colors in terms of the
   classes above, by hand.


Unfortunately you have to now type all methods exposed by the interfaces
Jumping and Colors and implement them. It's better than just one huge
class, because the Karel class is "thin" and just delegates to other
classes. It can be a PITA because it's still lines of code you have to
type, test and maintain.

Many IDEs will write the methods for you for Jumping and Colors. You'll
still have to implement the method bodies yourself though.

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