What are different types of inner classes ?

Nested top-level classes

If you declare a class within a class and specify the static modifier, the compiler treats the class just like any other top-level class.

Any class outside the declaring class accesses the nested class with the declaring class name acting similarly to a package. eg, outer.inner. Top-level inner classes implicitly have access only to static variables.There can also be inner interfaces. All of these are of the nested top-level variety.

Member classes

Member inner classes are just like other member methods and member variables and access to the member class is restricted, just like methods and variables. This means a public member class acts similarly to a nested top-level class.

The primary difference between member classes and nested top-level classes is that member classes have access to the specific instance of the enclosing class.

Local classes

Local classes are like local variables, specific to a block of code. Their visibility is only within the block of their declaration. In order for the class to be useful beyond the declaration block, it would need to implement a more publicly available interface.

Because local classes are not members, the modifiers public, protected, private, and static are not usable.

Anonymous classes

Anonymous inner classes extend local inner classes one level further.

As anonymous classes have no name, you cannot provide a constructor.