Implementing one interface using multiple classes

Question

This question was asked to me in an interview. Tired of googling here I am.

I have an interface with 100 methods. I don't want to implement all those 100 methods in a single class. Is there any way I could implement these 100 methods by using more than one class and not repeating the implementation ?

For Example : Class A implements first 10 methods(only). Class B implements next 10 methods(only) and so on.

Note : 1. All the classes which implements the interface must be concrete.

As far as my knowledge on java this isn't possible. He mentioned about adapter when he asked me this question. That made me think that there's a way to do it.

Can anybody clarify me on this ?

Answer 1

Write an adapter with empty implementation of the 100 methods

 class Adapter{
    //write your empty implementations here as similar to KeyListener in Java
    // They have written a keyAdapter and make use of key adapter.

    }

ie) class Adapter implements interface1{
    public void method1(){}
    public void method2(){}
     .....
}

You can extend the adapter class in some other class and just override the methods.

class A extedns Adapter{
    public void method1(){
}
}

ie)

Answer 2

The concept you describe is called partial classes and Java does not have such a concept.

Here is a similar answer: A way to implement partial classes in java