- It is a way of logically grouping classes that are only used in one place.
- It increases encapsulation.
- Nested classes can lead to more readable and maintainable code.
Increased encapsulation—Consider two top-level classes, A and B, where B needs access to members of A that would otherwise be declared
private. By hiding class B within class A, A's members can be declared private and B can access them. In addition, B itself can be hidden from the outside world.More readable, maintainable code—Nesting small classes within top-level classes places the code closer to where it is used.
As with class methods and variables, a static nested class is associated with its outer class. And like static class methods, a static nested class cannot refer directly to instance variables or methods defined in its enclosing class — it can use them only through an object reference.
Instance inner class
A non-static inner class has the outer class as an instance variable, which means it can only be instantiated from such an instance of the outer class:
An anonymous inner class can come useful when making an instance of an object which certain "extras" such as overloading methods, without having to actually subclass a class. In below example we are using Thread using anonymous inner class.
- Anonymous class is declared and initialized simultaneously.
- Anonymous class must extend or implement to one and only one class or interface resp.
- As anonymouse class has no name, it can be used only once.
Below example explains mainly we have 3 type of inner classes.
