Question

When would you choose to use an abstract class instead of an interface

Answer 1

from my understanding abstract interfaces are more a way to link things that do not have too many commonalities (classes that do not have a blatant inheritance relationship) they just provide general directions regarding what type of behavior should be implemented while abstract classes promote more code re-use and shared fields.

Answer 2

I would use an abstract class when there is ...

1. a shared state or implementation (common base of functionality)
2. partial implementations (if some methods need a default implementation and needs to be abstract for subclasses to override)
3. Hierarchical Relationships (is-a relationships)

Don't use an abstract class when...

1. Multiple classes need to implement the same set of methods but are unrelated in their inheritance hierarchy.
2. You need to define a pure contract without any shared state or implementation.

It really comes down to whether you need shared implementation (abstract class) or just behavioral specification (interface).

Answer 3

You'd use an abstract class when you need to provide shared implementation details or fields along with method declarations for subclasses. Abstract classes are ideal for creating a base class with common functionality. In contrast, interfaces are better when you only need to define a contract (method signatures) without shared implementation.

Answer 4

An abstract class is preferred over an interface when you need a class that allows the sharing of common code functionality, with an inheritance concept in between classes like the is-a relationship, whereas interfaces implement the common functionality between closely related classes. Abstract classes are useful when you want to update a common behavior in the base abstract class it updates the inheriting classes as well.