Java | Static VS Non-Static Nested Classes

Static VS Non-Static Nested Classes

     1.      The instance of static nested class is created without the reference of outer class, which means it does not having enclosing instance

The instance of non-static nested class is created with the reference of object of outer class, in which it has defined , this means it has enclosing instance

    2.      Static nested classes does not need reference of outer class. Non-static nested class requires the outer class reference . you can’t create instance of inner class without creating instance of outer class

   3.      Another difference between static and non-static nested classes is that you can’t access non-static members example: methods and fields into nested static class directly, if you do, you will get error like non-static member can’t be used in static context. While inner class can access both static and non-static no of order classes

If you make a nested class non-static then it also referred as inner class

Class outer

     {

 Private static String message =  ”hello”;

//static nested class

            Private static class MessagePrinter

                        {

//onlystatic member of outer class is directly accessible in nested static class

                        Public void PrintMessage()

                                    {

//compile time error if message field is not static

            System.out.println(“message from nested static class : “ + message);

                                    }

                        }

//non-static nested class also called inner class

            Private class inner

                        {

//both static and non-static member of outer class is accessible in the inner class

                        Public void display()

                                    {

           

System.out.println(“message from non-static nested  class : “ + message);

                                    }

                        }

//create static and non-static nested classes

            Public static void main(String[] args)

                        {

//creating instance of nested static class

            Outer.MessagePrinter printer = new outer. MessagePrinter();

//calling non-static method of nested static class

                        Printer. printMessage();

//creating instance of  non-static nested class

                        Outer.Inner inner = outer.new Inner();

//calling non-static method of inner class

                        Inner.display();

//we can also combine above steps

                        Outer.Inner nonstaticIner = new Outer.new inner();

                        Non-staticIner.display();

                        }

            }

Output :    

                       message from nested static class : hello

                       message from nested static class : hello