What's Abstract class , what's the use of it . What's interface , how it appears to a important part of Service layer.

Question

Accepted Answer

Abstract class is a class that cannot be instantiated, while interface is a contract that defines methods.

Abstract class can have both abstract and non-abstract methods, while interface can only have abstract methods.
Abstract class can have instance variables, while interface cannot.
Abstract class is used for code reusability and polymorphism, while interface is used for achieving abstraction and loose coupling.
In service layer, interface is used to define the contract between the service and the client, while the implementation is done in the concrete class.

Accepted Answer

Abstract class is used for code reusability and polymorphism, while interface is used for achieving abstraction and loose coupling

Popular interview questions of Software Engineer