exam poo

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

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

public class Main {

    public static void main(String[] args) {
        A a = new B();
        a.f(new B());
        System.out.println(A.class.isInstance(new B()));
    }
}