What is Abstract Class

In programming languages, an abstract type is a type in a nominative type system that cannot be instantiated directly; a type that is not abstract – which can be instantiated – is called a concrete type. Every instance of an abstract type is an instance of some concrete subtype.

Why Abstract Class?

Consider using abstract classes if any of these statements apply to your situation:

• You want to share code among several closely related classes.
• You expect that classes that extend your abstract class have many common methods or fields or require access modifiers other than public (such as protected and private).
• You want to declare non-static or non-final fields. This enables you to define methods that can access and modify the state of the object to which they belong.