Suppose I have

class Data{
...
}

class DData extends Data{
...
}

interface A {
  Data getData();
}

interface DA{
  DData getData();
}

What I want from DA is to focus on a special kind of Data, while it
still can be used as A. But it does not compile. How can I fixed it?

Can I do this:

interface A {
  void getData(Data data);
}

interface DA{
  void getData(DData data);
}