Interface vs Abstract Class
Interfaces:A class may inherit several interfaces.
Abstract Class:A class may inherit only one abstract class.
Interfaces:An interface cannot provide any code, just the signature.
Abstract Class:An abstract class can provide complete, default code and/or just the details that have to be overridden.
Interfaces:An interface cannot have access modifiers for the subs, functions, properties etc everything is assumed as public
Abstract Class:An abstract class can contain access modifiers for the subs, functions, properties
Core VS Peripheral
Interfaces:Interfaces are used to define the peripheral abilities of a class. In other words both Human and Vehicle can inherit from a IMovable interface.
Abstract Class:An abstract class defines the core identity of a class and there it is used for objects of the same type.
Usage in Application
Interfaces:If various implementations only share method signatures then it is better to use Interfaces
Abstract Class:If various implementations are of the same kind and use common behaviour or status then abstract class is better to use.
Interfaces:Requires more time to find the actual method in the corresponding classes.
Abstract Class:Compare to Interface it is very fast
Fields and Constants
Interfaces:No fields can be defined in interfaces
Abstract Class:An abstract class can have fields and constrants defined
Main Limitation of Interface
If we add a new method to an Interface then we have to track down all the implementations of the interface and define implementation for the new method
in all derived class.
Main Limitation of Abstract Class
A class may inherit only one abstract class.