What is use of static inner class in Java?

Inner classes cannot declare static members other than compile-time constants .

1) First and most important difference between Inner class and nested static class is that Inner class require instance of outer class for initialization and they are always associated with instance of enclosing class . On the other hand nested static class is not associated with any instance of enclosing class.

Java static nested class A static class is a class that is created inside a class, is called a static nested class in Java. It cannot access non-static data members and methods . It can be accessed by outer class name. It can access static data members of the outer class, including private.

Nested classes that are declared static are called static nested classes. A nested class is a member of its enclosing class. Non-static nested classes (inner classes) have access to other members of the enclosing class , even if they are declared private.