Question

Suppose I have abstract class A and abstract class B which inherits from A, and I create an object of class A as shown:

abstract class A {
   void func1();
}

abstract class B extends A {
   void func2();
}

A objectA = new A() {
   func1(){
      //implementation
   }
};

Is there a way for me to do something like this:

B objectB = new B(objectA) {
   func2(){
      //implementation
   }
};

so that objectB gets the implementation of A’s functions from objectA?

Answer 1

I understand what you want to do. Such things are possible in Ruby for example. In Java it’s not possible that way because

new A() { 
   func1(){  } 
}; 

is not of type A but an anonymous subclass of A which is not a superclass of B. The compiler generates some $1 class for that.

But in general try another approach: “Favor composition over inheritance”. Then are able to combine func1 and func2 somewhere just by using two Strategy classes. So if B is not using any state of A you could delegate to objectA (which has to be final then):

B objectB = new B() { 
   func1(){ 
     objectA.func1()
   } 
   func2(){ 
     //implementation 
   } 
}; 

This is similar to bashflyng’s answer, but more direct.