Using abstract classes and Interfaces

Question

If I have three classes

class A

class B extends A

class C extends A

Would using abstract classes or interfaces give me any type of errors or affect the way I implement the program?

Answer 1

Unless you need to share implementation, favor interfaces.

If you need to share implementation, think carefully if an abstract class is the right way to accomplish this.

Inheritance is a powerful tool, but can easily create an unmaintainable mess (I have been guilty here).

But to answer your question - no, there is nothing inherent in this setup that would cause an "error".

Answer 2

You should generally prefer interfaces whenever you can. Java's lack of multiple inheritance quickly becomes a limiting factor if you use classes for that.

Answer 3

Yes. Abstract classes trade a shorter way of reusing implementation for the flexibility to provide multiple interfaces to the same object.

Unless you're playing code-golf, choosing the flexibility of interfaces is usually the better option.