Inherit an inner class

[ying lam]

Hi,

Can you please tell me how can I inherit from an inner class of another class?

 

public class A {
    
public class InnerA {
}

}

But how can I create an inner class in B which inherits from InnerA?

public class B{ 
    A a;

public class innerB extends InnerA {

}

}

 

I get an error saying "No enclosing instance of type A is assessible to invoke the super constructor and explicitly qualify its super constructor innvocation with an instance of A.

Thank you.

[W. Joe Smith]

Being the extreme expert in Java that I am (all of 2 months) I don't think you can can have a class inherit from an inner class if it is not also an inner class of the same class (if at all). Since an inner class has its lifecycle defined by the outer class and classes that inherit from it would have the same status, I believe. Again, I am not an expert but this is the way it appears to me. I could be wrong.

[Campbell Ritchie]

Try changing it to a nested class (labelled "static"). That might work.

[Paul Clapham]

Well, for a start you have to extend A.InnerA, since that's the official name of the class.

[Henry Wong]

Yes, it is possible for an inner class of one class to extend the inner class of another class -- but it is convoluted, so don't do it.

Why? An inner class doesn't exist outside the context of an outer class. So, when an inner class inherits from another inner class, you have to have both the outer classes in context. The syntax is also weird too.

Henry

[Henry Wong]

The syntax is also weird too.

But if you are interested, it looks something like this....

public class A {
    public class InnerA {

    }
}

public class B {
    public class InnerB extends A.InnerA {
        public InnerB (A a) {
            a.super();
        }
    }
}

And instantiations of the inner classes look something like this...

A.InnerA a = new A().new InnerA();
B.InnerB b = new B().new InnerB(new A());

Henry

[Henry Wong]

BTW, forgot to mention.... If the outer classes inherit from each other, then it is less convoluted.

public class B extends A {
    public class InnerB extends A.InnerA {
        public InnerB () {

        }
    }
}

Henry

[Ankit Garg]

Just take a look here...