JAVA

use of nested class in java

In Java, it is possible to define a class within another class, such 
classes are known as nested classes. They enable you to logically group 
classes that are only used in one place, thus this increases the use of 
encapsulation, and creates more readable and maintainable code.

Java Nested and Inner Class

class OuterClass {
    // ...
    class NestedClass {
        // ...
    }
}

nested class in java 8

A regular nested class cannot access members of its outer class. But a nested class marked as an inner class can.