RE: Understanding Implements

I'm working toward the "ah-HA!" here, and I deeply appreciate the discussion
to date...

I'm missing the advantage of the extra layer of abstraction involved in
using interface Noisable.  Since every class that implements Noisable will
be required to have a makeSound() method anyway, what does the empty
interface bring to the table?

If this is way too "newbie" tell me to go away and read some more.  I will
do the right thing, I promise!

Buck 

> -----Original Message-----
> From: Joe Teff 
> Sent: Wednesday, March 21, 2001 10:20 AM
> To:   JAVA400-L@midrange.com
> Subject:      RE: Understanding Implements
> 
> The following is an interface, stored in a .java source file and compiled
> the same as classes:
> 
> public interface Noisable {
>    public void makeSound();
> }
> 
> Notice that the method only contains the signature and no implementation.
> Methods in an interface are abstract. The interface only requires that you
> supply the method(s) listed. There is no inheritence here.
> 
> This class will implement that interface:
> 
> public class Airplane implements Noisable {
>    // various methods and data
>    public void makeSound() {
>       // code to here to make airplane noise
>    }
> }
> 
> This class will not compile unless I code all methods listed in the
> interface, hence the "contract" reference.
> 
> Now lets make an application that generates sounds:
> 
> public class GenerateSounds {
>    public static void blareItOut( Noiseable obj ) {
>       obj.makeSound();
>    }
> }
> 
> I can call GenerateSounds.blareItOut(xxx) where xxx is an object created
> from any class that implements Noisable. The actual code to make the noise
> is coded into each class's makeSound() method, thus each one will do it
> slightly different. blareItOut() doesn't care how the code works, it just
> cares that the appropriate method is there. It doesn't even care what kind
> of object (class) it even is. The only thing it knows is that it has to
> have a makeSound() method that it can call.
> 
> Joe Teff
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