Defination
A class declared inside a class is known as nested class.
Syntax
Class Outer_Class_Name{
...
...
Class Inner_Class_Name{
...
...
}
}
| Types of nested classes There are two types of nested classes non-static inner classes and static nested classes.
 |
Difference between non-static inner classes and static nested classes in Java?
Non-static inner classes have access to other members of the enclosing class, even if they are declared private.
Static nested classes do not have access to other members of the enclosing class.
Difference between narmal classes and nested classes in Java?
A nested class is a member of its enclosing class.
As a member of the
OuterClass, a nested class can be declared private, public, protected, or package private.
(Recall that outer classes can only be declared
public or package private.)Advantage of nested classes?
Why Use Nested Classes?
Compelling reasons for using nested classes include the following:- It is a way of logically grouping classes that are only used in one place: If a class is useful to only one other class, then it is logical to embed it in that class and keep the two together. Nesting such "helper classes" makes their package more streamlined.
- It increases 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. - It can lead to more readable and maintainable code: Nesting small classes within top-level classes places the code closer to where it is used.
static nested class
A static class that is created inside a class is known as static nested class.
- It can access static data members of outer class including private.
- It cannot refer directly to instance variables or methods defined in its enclosing class: it can use them only through an object reference.
- static nested class cannot access non-static (instance) data members directly.
