Types of Nested classes

There are two types of nested classes non-static and static nested classes.The non-static nested classes are also known as inner classes.

• Static nested class
• Non-static nested class (inner class)
1. Member inner class
2. Anonymous inner class
3. Local inner class

Static nested class:-

For example, to create an object for the static nested class, use this syntax:

OuterClass.StaticNestedClass nestedObject =new OuterClass.StaticNestedClass();

Non-static nested class (inner class)

To instantiate an inner class, you must first instantiate the outer class. Then, create the inner object within the outer object with this syntax:

OuterClass.InnerClass innerObject = outerObject.new InnerClass();

//Example:-Static nested class

package staticnested;

public class OuterClass {

           

            String fname="Govind";//non static member

            static String mname="Ballabh";//static member

            private static String lname="khan";//private and static member

           

            public  void myPageName()//non static member

            {

                        System.out.println("Java Technology");

            }

           

            static class StaticNestedClass

            {

                        public void displayName()

                        {

                                    //System.out.println("FirstName="+fname);

                                    System.out.println("Middle Name="+mname);

                                    System.out.println("Last Name="+lname);

                                    //myPageName();//compile time error bcz it is non static method

                                   

                        }

            }

}

=================================================================================

package staticnested;

public class OuterClassMain {

               

                public static void main(String[] args) {

                                OuterClass.StaticNestedClass oc=new OuterClass.StaticNestedClass();

                                oc.displayName();

}

}

o/p:---------------

Middle Name=Ballabh

Last Name=khan

//Example:-Non static nested class

package NonStaticNested;

public class OuterClass {

                   

                    String fname="Govind";//non static member

                                static String mname="Ballabh";//static member

                                private static String lname="khan";//static with private member

                               

                                public  void myPageName()//non static member

                                {

                                                System.out.println("Java Technology");

                                }

                               

                                 class NonStaticNestedClass

                                {

                                                public void displayName()

                                                {

                                                                System.out.println("FirstName="+fname);

                                                                System.out.println("Middle Name="+mname);

                                                                System.out.println("Last Name="+lname);

                                                                myPageName();

                                                }

                                }

                }

==================================================================================

package NonStaticNested;

public class OuterClassMain {

               

                public static void main(String[] args) {

                               

                                OuterClass oc=new OuterClass();

                                OuterClass.NonStaticNestedClass ons= oc.new NonStaticNestedClass();

                    ons.displayName();

                }

}

o/p:------------------------

FirstName=Govind

Middle Name=Ballabh

Last Name=khan

Java Technology

Difference between static and inner(non-static nested) classes

§   Static nested classes do not directly have access to other members(non-static variables and methods) of the enclosing class because as it is static, it must access the non-static members of its enclosing class through an object. That is, it cannot refer to non-static members of its enclosing class directly.

§      Non-static nested classes (inner classes) has access to all members(static and non-static variables and methods, including private) of its outer class and may refer to them directly in the same way that other non-static members of the outer class do.