Question

Is it necessary to parametrize the entire interface for this scenario, even though Bar is only being used in a single method?

public interface IFoo<T>{

    void method1(Bar<T> bar);

    //Many other methods that don't use Bar....

}  

public class Foo1 implements IFoo<Yellow>{

    void method1(Bar<Yellow> bar){...};

    //Many other methods that don't use Bar....

}


public class Foo2 implements IFoo<Green>{

    void method1(Bar<Green> bar){...};

    //Many other methods that don't use Bar....

}

Answer 1

No, it’s not necessary from a syntactic standpoint. You can also do this:

public interface IFoo {

  <T> void method1(Bar<T> bar);

  /* Many other methods that don't use Bar…  */

}

Or this:

public interface IFoo {

  void method1(Bar<?> bar);

  /* Many other methods that don't use Bar…  */

}

The correct choice depends on the semantics of IFoo and what its implementations are likely to do with the Bar instances they receive through method1.