Wait what?

package de.pelikompendium;

class A {
    public void f(A p) {
        System.out.println("A.f(A)");
    }
}

class B extends A {
    public void f(A p) {
        System.out.println("B.f(A)");
    }

    public void f(B p) {
        System.out.println("B.f(B)");
    }
}

class A2 {
    public void f(A2 p) {
        System.out.println("A2.f(A2)");
    }

    public void f(B2 p) {
        System.out.println("A2.f(B2)");
    }
}

class B2 extends A2 {
    public void f(A2 p) {
        System.out.println("B2.f(A2)");
    }

    public void f(B2 p) {
        System.out.println("B2.f(B2)");
    }
}

public class Main {
    public static void main(String[] args) {
        A a = new B();
        B b = new B();
        A2 a2 = new B2();
        B2 b2 = new B2();

        a.f(b); // B.f(A)
        a2.f(b2); // B2.f(B2)
    }
}