Inner Classes

Question 1

What is a nested class?

Answer 1

A class that is declared inside another class.

Question 2

Why do we use nested classes?

Answer 2

Logical grouping: if one class is useful only to one other class, then we can nest them together in one file.
Encapsulation: Nested classes increase encapsulation.
Code Clarity: Makes the code more readable, only top-level classes are exposed. Helper classes are kept hidden.

Question 3

What is a nested interface?

Answer 3

A nested interface is an interface that is declared inside another interface. By default it is static. It is also known as a static interface.

Question 4

Can an Interface be defined in a Class?

Answer 4

Yes we can define a Static Nested interface within a class. Only the enclosing class can access it.