RE: Interfaces, abstract classes. Why?

["Jones, Ashley C" <Ashley.Jones@bellsouth.com>]

to expand on Steve's example

Lets say you are working on a project called zoo
and you write code which when you are looking at a certain animal
you can hear its typical noise.  

Lets say different people are writing each animal.  You would create an
interface( or Abstract class) called Animal, which would define the method
makeNoise and
tell each programmer that they had to implement Animal.  That way you would
know
that in your code all you have to do is call the method Animal.makeNoise()
and you wouldn't have to figure out what the animal is first. 

-----Original Message-----
From: Steve Ardis [mailto:scardis@yahoo.com]
Sent: Wednesday, April 02, 2003 2:37 PM
To: ajug-members@ajug.org
Subject: Re: Interfaces, abstract classes. Why?



Interfaces allow you to keep logical layers of your
code from knowing about a specific implementation. 
For example, it allows me to write client code that
adheres to a contract defined by an interface.  As
long as my code only directly references the
interface, I can determine at runtime the
implementation class to use (do a Google search on
Factory Method).

An abstract class allows for things like OO's
polymorphism to occur.  By defining an "Animal" class,
I can define an abstract method "makeNoise()" - it is
up to the "Dog" and "Cat" subclasses of "Animal" to
determine what happens when "makeNoise()" is called.

Hope this helps



--- Jennifer Fisher <jenniferfisher@programmer.net>
wrote:
> Hi all.  I hope someone can help me understand
> better.
> 
> What are the uses for interfaces and abstract
> classes?  Why would one need them in a project and
> what for?
> 
> Thank you in advance.
> 
> 
> 
> 
> 
> Jennifer Fisher
> Developer, Gaye Systems
> IITP 2.0
> 
> -- 
>
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