Nested classes in Java

Java allows to define a class inside another class. When a class is nested inside a another class, it is said as nested class.

When nested classes can be used ?

If a class needs to be used only in a single other class, you can nest that class inside the other class.
If we need to increase the encapsulation or hiding data, we can use nested classes. By making the nested class as private, we can hide the nested class from the outer world.
Nested classes also increases readability of a program when properly grouped.

class Outer_class{

class Inner_class{

//statements

}