Comparing abstract base class and Interface

[Tony Johansson]

Hello!

If you compare an abstract baseclass and an Interface and you only look at
the datamembers what exactly is that
differ or is the same. For example can you have datamember in both or just
in one of these.

//Tony

[Casper B]

Re: Comparing abstract base class and Interface

It's a good question, one that everyone ask themselves when learning Java.

You have probably heard the saying "Program to interfaces, not
implementations " countless times. In this regard, an interface does not
qualify to just the java interface construct, but covers also abstract
classes.

One clear disadvantage of an abstract class, is that naturally you have
already used your single inheritence option. However, you often meet
abstract base classes in frameworks where some default behavior is
needed (event handling, required initiations etc.).

As you probably know, interfaces are Java's way of providing a multiple
inheritance feature. But the feature is implemented through composition
rather than inheritance. This is where a bunch of well-defined design
patterns like Strategy and Decorator comes to play.

/Casper