Question

Possible Duplicate:
Interface vs Abstract Class (general OO)

I’m not exactly clear on the difference.

Thanks

Answer 1

They are quite similar but there are some important technical differences:

• An abstract class allows you to provide a default implementation for some of the methods but an interface does not allow you to provide any implementations.
• You can implement multiple interfaces but you can only inherit from one abstract class.

These differences affect how the two techniques should be used:

• You should use an interface to define a contract.
• An abstract class can be useful to reuse code… but be aware that it is not the only way to reuse code. You should also consider other approaches such as containment.