inner class

[yogesh srinivasan]

Hi,

In a mock test i was seeing the following question

which is true regarding Inner Class

the right ANSWERES where

a) An instance of a top level nested class can be created with out an instace of its enclosing class

b) to create an instance of a member class an instance of its enclosing class is required


I'm not able to relate the ans (a)


IT would be great if any one could explain it with an example........!!!1

[Priyam Srivastava]

An instance of a top level nested class can be created with out an instace of its enclosing class

it means if you are creating the object of inner class within any method of outer enclosing class you don't need the instance of Outer class.

Consider this example::

class Outer {
   class Inner {}
   public void createInner() {
      Inner in = new Inner(); //no need for Outer Reference
   }
   public static void main(String[] args) {
     Outer out = new Outer();
     out.createInner();
   }
}

[Burkhard Hassel]

Howdy Yogesh!

Sorry, but the example of Priyam is completely wrong. It is a regular inner class, not a top level nested class. And despite the comment "no outer ref. needed" it IS needed, as you can see in the main method.

A "top level nested class" is just the same as a "static inner class".

The first terminus is official and more correct since these static inner classes aren't real inner classes at all.


Do you still need an example or do you understand this already?

Bu.

[Priyam Srivastava]

oops!!! mistake accpeted !! thanks for a reminder..

i should have written this::

class Outer {
  static class Inner{}
}
 
class MakeInner {
   public static void main(String[] args) {
     Outer.Inner in = new Outer.Inner(); //No need for Outer reference !!
   }
}

[Burkhard Hassel]

[yogesh srinivasan]

Hi Burkhard Hassel

A "top level nested class" is just the same as a "static inner class".

Need some more explanation for the above statement as i cant relate them.... ;


More over i need to know wat is the need for static class...and how the constructors behave for this context when compared to a normal class
[ August 06, 2007: Message edited by: yogesh srinivasan ]