How to implement function in interface with generic argument types?-CodePudding

public interface Page<T> {
  T nextPage();
}

And it's implementation

public class ConcretePageA implements Page<TypeA> {
  public TypeA nextPage() {
    // do stuff
  }
}

Then I have an interface that consumes Page

public interface Source {
  <T> int getData(Page<T> page)
}

And its implementation

public class ConcreteSourceA implements Source {
  public int getData(Page<TypeA> page) {   //error: getData in ConcreteSourceA clashes with getData in Source
    // do stuff
  }
}

I tried this but it won't work either

public class ConcreteSourceA implements Source {
  public <TypeA> getData(Page<TypeA> page) { // error: expect com.foo.TypeA but got TypeA
    // do stuff
  }
}

When I do the above I get a compile error saying

getData in ConcreteSourceA clashes with getData in Source

I know I am doing something wrong, but how do i fix it while still having multiple implementations that uses different types?

Am I just doing this wrong in the first place? Is Generics not the right way to go about this?

CodePudding user response：

It looks like you want to make Source generic much like Page is - like so:

public interface Source<T> {
  int getData(Page<T> page);
}

You can then define implementations that only implement certain specializations of that like

public class ConcreteSourceA implements Source<TypeA> {
  public int getData(Page<TypeA> page) {
    // do stuff
    return 0;
  }
}