Java: anonymous class as subclass from existing implementing an interface?

Question

I have interface IA, interface IB extends IA and class A implements IA.

Now I want to create an anonymous class which extends from A and implements IB.

How would that look like? I thought about something like this:

new A() implements IB { /* ... */ }

( Error: Type mismatch: cannot convert from A to IB )

or:

new IB() extends A { /* ... */ }

( Error: Syntax error on token(s), misplaced construct(s) )

Or is it not possible to create something like that as an anonymous class?

I think your design is wrong.Class A already offers the functionality of IA and you want it to implement also IB that extends IA? Class A should just implement IB — Cratylus
– Cratylus, Commented Oct 20, 2010 at 14:23
Class A should not (and does not and can not) implement IB (because it must not be abstract). — Albert
– Albert, Commented Oct 20, 2010 at 14:32

Jim Downing · Accepted Answer · 2010-10-20 14:06:29Z

4

I suppose you could create an abstract, named inner class that combined the two and extend that with your anonymous class.

   private static abstract class AB extends A implements IB {};
    ...
   new AB() {};

Bit clumsy, but I don't think you can implement both.

answered Oct 20, 2010 at 14:06

Jim Downing

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