How to override methods with an interface in java

Question

I have an interface I, two classes A & B that implement it and a list with generic type the interface I, so it can contain both objects of type A & B.

class A implements I
class B implements I
List<I> myList

I would like to write (in a separate class) two methods process( A a ) and process( B b ) so I can loop through the list and for each element call process( i ) and java will automatically (unbox?) the object and invoke the correct method.

class D{
    processList(){
        for( I i : myList ){
            process( i ); // invoke either process(A) or process(B) based on instanceof
        }
    }
    public void process(A a){...}
    public void process(B b){...}
}

I know I can do this by invoking 'instanceof' on each element in the list and then if-else to call the different methods, but there must be a better way.

In a MVC scenario, classes A and B are in the Model, while class D is in the Controller, thus the need for separation.

Can anyone help?

Answer 1

there must be a better way.

There is. Add the method process() to the interface I . Then you can call process on the items while you iterate the List<I> -

List<I> list = new ArrayList<>(); 
// populate list with A and B instances, then
for (I i : list) {
  i.process();
}

Obviously A and B must then provide concrete implementations of process() .