Can a nonstatic member type be used without association with an instance of the enclosing class?

user10082400 :

Can a nonstatic member type be used without association with an instance of the enclosing class?

For example

class Outer {    
    class Inner {       

    }    
}

public class Demo {
    public static void main(String args[]) {

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

    }    
}

In Outer.Inner inner = o.new Inner(), does Outer.Inner use Innerwithout association to an instance of the enclosing class?

Is there other example where a nonstatic member type can be used without association with an instance of the enclosing class?

Thanks

Sweeper :

does Outer.Inner use Inner without association to an instance of the enclosing class?

In a sense, yes, because Outer.Inner refers to a type. And you never need instances in order to use types.

I think you mistakenly thought that Outer.Inner shouldn't work because there are an infinite number of different types called Inner, created with different instances of Outer. You might have thought that if I have two different instances of Outer, o1 and o2, they will create different Inner types.

But this is entirely not true. You can totally do something like this:

Outer o1 = new Outer();
Outer o2 = new Outer();
Outer.Inner inner1 = o1.new Inner();
Outer.Inner inner2 = o2.new Inner();
inner2 = inner1;

So Outer.Inner is just one type. It just so happens to be that an instance of this type requires an instance of Outer in order to be created.