Re: Understanding Classes

From:
alexandre_paterson@yahoo.fr
Newsgroups:
comp.lang.java.programmer
Date:
Wed, 22 Jul 2009 16:22:36 -0700 (PDT)
Message-ID:
<074db482-34cd-41cf-b2ba-6598a4ab0a14@24g2000yqm.googlegroups.com>
On Jul 21, 1:37 pm, brian void <brian.voi...@gmail.com> wrote:
....

But then if I want to make Karel jump I have to create and instance of
KarelJumps rather the SuperKarel. But because KarelJumps is a
different object then KarelColor I couldn't use any of its methods.

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


If your SuperKarel can actually jump and color (is it colorizing stuff
, does he have a color, is it colorizable?) then, yup, it's going to
be
"one object" responding to such messages (jump / color / etc.) (not
with
the way you modelled it that said, see what markspace suggested to
you).

But from your code you won't necessarily always refer to your
SuperKarel
as a SuperKarel.

If you have, amongst other, those interfaces:

interface Jumping {
    ... more methods

}

interface Colors {
   ... more methods

}

Then in your code you may have lines like this:

  Jumping j = findClosestJumpableRobot();
  j.jump();

(you re referring to your SuperKarel simply as a Jumping object,
because that's all your care about here)

  Colors c = findFirstColorizableRobotAtSprayDistance();
  c.colorize();

The cool thing is that you may have the following:

  Kangaroo implements Animal, Jumping {
   ...
  }

and then:

  Jumping j = findClosestJumpableThing();

and that line may return you either a Kangaroo or
a SuperKarel or something that can respond to the
"jump()" message but that hasn't been identified
yet in your customer's problem space.

That's the beauty of OO :)

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