Forcing Java generic parameters to be of the same type

Question

How can a similar functionality be achieved without errors?

class A {
   void f(K x) {}
}

void foo(A a, X x) {
    a.f(x); // AN         


        

Answer 1

Keeping in mind the PECS rule, and given the way you are using X, you should be specifying as a lower instead of upper bound:

void foo(A a, X x)

This way no compiler errors are produced, and you have the most general signature applicable.