Question

Assume that I have these three classes:

class Foo {
    void fn() {
        System.out.println("fn in Foo");
    }
}

class Mid extends Foo {
    void fn() {
        System.out.println("fn in Mid");
    }
}

class Bar extends Mid {
    void fn() {
        System.out.println("fn in Bar");
    }

    void gn() {
        Foo f = (Foo) this;
        f.fn();
    }
}

public class Trial {
    public static void main(String[] args) throws Exception {
        Bar b = new Bar();
        b.gn();
    }
}

Is it possible to call a Foo‘s fn()? I know that my solution in gn() doesn’t work because this is pointing to an object of type Bar.

Answer 1

It’s not possible in Java. You can use super but it always uses the method in immediate superclass in type hierarchy.

Also note that this:

Foo f = (Foo) this;
f.fn();

is the very definition of polymoprhism how virtual call works: even though f is of type Foo, but at runtime f.fn() is dispatched to Bar.fn(). Compile-time type doesn’t matter.