When to use an interface instead of an abstract class and vice versa?

Question

This may be a generic OOP question. I wanted to do a generic comparison between an interface and an abstract class on the basis of their usage.

When wou

Answer 1

When to prefer an abstract class over interface?

1. If one plans on updating a base class throughout the life of a program/project, it is best to allow that the base class be an abstract class
2. If one is trying to build a backbone for objects that are closely related in a hierarchy, it is highly beneficial to use an abstract class

When to prefer an interface over abstract class?

1. If one is not dealing with a massive hierarchical type of framework, interfaces would be a great choice
2. Because multiple inheritance is not supported with abstract classes(diamond problem), interfaces can save the day