Invoking interface object methods

Question

I have a interface Appendable in which I have a method appendTo(Appendable obj) . Classes TextMessage and EncMessage extend class Message , which implements Appendable .In TextMessage I have to implement method appendTo(Appendable obj) so that if obj is an instance of TextMessage the method is supposed to change its data members. But I can't access TextMessage set methods.So my question is how can I access and use them?

Answer 1

You could implement appendTo of TextMessage like this :

void appendTo (Appendable obj) {
  if (obj instanceof TextMessage) {
    TextMessage msg = (TextMessage) obj;
    msg.setXXX (...);
    ...
  }
}

I had to make some assumptions without actually seeing your code.