Question

I understand multiple inheritance and interface to an extent. Is it possible to use Multiple inheritance to achieve my requirement?

I have classes A,B,C,D which implements interface InterA, InterB, InterC, InterD respectively. I want a class ABCD which should have all the methods of A, B, C, D. Then I want the declared methods in InterA, InterB, InterC, InterD available at class ABCD.

I have implementations of methods in InterA, InterB, InterC, InterD already defined in classes A,B,C,D, which I don’t want to define again in class ABCD. How can I do this in Java?

Answer 1

Since there is no multiple inheritance in Java you have to resort to aggregation:

class ABCD implements InterA, InterB, InterC, InterD
{
   A implA;
   B implB;
   C implC;
   D implD;

   ABCD(A pimplA, B pimplB, C pimplC, D pimplD)
   {
     implA = pimplA;
     implB = pimplB;
     implC = pimplC;
     implD = pimplD;
  }


  // @overidde methods from InterA as return implA ->method();
  // @overidde methods from InterB as return implB ->method();
  // @overidde methods from InterC as return implC ->method();
  // @overidde methods from InterD as return implD ->method();
}

That way you just have to create some instances of A, B, C and D and pass them at the construction of ABCD. Then ABCD just have to call their methods.

By doing that you will reuse the implementations of A, B, C and D.