Hi,

You are right, that an abstract class can be a substitude for an
interface in some cases.

Note however, that interfaces allow multiple inheritance where classes
don't.

Ciao,
Ingo

No, can't.
You can not create class even with two "extended" parents, but you may
"implement" as many interfaces as you like.

Interfaces are something like drawing pencils and classes like
painting colors. Even Van Gogh used pencils ... and you say we should
not use interfaces!

I bet this is homework. Oh well, I've already written the reply.

Not in Java, no. The things you can't put in interfaces -- specifically,
instance variables -- mean that you can inherit, ie, implement,
multiple interfaces without having to solve some knotty efficiency
issues.

Premise false.

På Wed, 28 Feb 2007 14:49:04 +0100, skrev sundarvenkata  
<sundarvenkata@gmail.com>:

Only parially, because the single class inheritance it shares with  
Smalltalk and C# (among others) means you can only inherit in one  
continous line. For the purposes of the type system, an interface is a  
class with only public abstract methods and public static fields. But the  
methods only have a signature, not any implementation you can delegate to  
so they avoid the "diamond" problem of multiple inheritance. So unlike  
classes that allow implementations, you can have many interfaces  
implemented by a class. (You still have a variant of the diamond problem  
if two interfaces use different semantics for the same method signature  
though.

Yes, it would be like adding byte, short, char and int when all can fit  
inside a long. :P