Innner class in Interface

[Malatesh Karabisti]

interface MyInterface {
class  MyInnerClass {    }
}

Above code compiles without any error and looks fine. I know in an interface all the variables are implicitly public final static and all methods are abstract and coderanch.

Can any body please explain the inner class declared in the interface are by default static ?

[Ankit Garg]

non-static inner classes cannot have static members in them but static inner classes can, try to create a static variable in MyInnerClass and see if it compiles ...

[Malatesh Karabisti]

public  class Test1 
{ public static void main(String[] args) 
    { System.out.println("Hello World!"); }
}

interface MyInterface {
class  MyInnerClass { 
static int a=10;
int b=10;
}
}

Above code compiles fine,in which the inner class has both static and instance variables

[Javin Paul]

Its good to know about it but what could be the usage of this having an interface and then having an Inner class ?

Based on my experience I only prefer Inner class if its closely related to outer class and not required in any other places or not shared , while interface is
to define contract for various implementation.

[Malatesh Karabisti]

As per my knowledge this is bad desgn.In fact I thought it is highly impossiable to write a inner class in a Interface. I found out this one while exploring. I just want to find out how this works and what is the purpose behind this