public class Test {

    public static void main(String[] args) {
        C obj = new D(); // the object is actually a D
        A a = obj.method(); // actually calls the method returning a B
        System.out.println(a.getClass()); // its a B
    }
}

class A {
}

class B extends A {
}
// B is sub-class
// B is 'narrower'

class C {

    A method() {
        return new A();
    }
}

class D extends C {
//Overriding method() in father class A

    B method() {
        return new B();
    }
}