Can you explain the difference between abstract classes and interfaces in object-oriented programming, and when would you use one over the other?

Abstract Classes vs Interfaces in Object-Oriented Programming

Abstract classes and interfaces are both important concepts in object-oriented programming. Here is a breakdown of the main differences between the two:

Abstract Classes:

• Abstract classes can have both abstract (non-implemented) and concrete (implemented) methods.
• Abstract classes can have instance variables.
• Subclasses extend only one abstract class.
• Abstract classes are good when some methods have a common implementation among subclasses.

Interfaces:

• Interfaces can only have abstract methods (methods without implementation).
• Interfaces cannot have instance variables.
• Subclasses can implement multiple interfaces.
• Interfaces are used to define a contract for classes that implement them.

When to Use One Over the Other:

Use abstract classes when you have a common functionality to implement across a set of related classes. Use interfaces when you want to enforce a contract that multiple unrelated classes can implement. In general, favor interfaces over abstract classes to promote loose coupling and easier maintainability.