Inheritance and polymorphism in Java

Question

I have 2 classes: Triangle and RightAngledTr. RightAngledTr inherits from Triangle. The code is as follows:

The Triangle class:

class Triangle {
    public void draw() { 
        System.out.println(“Base::draw\n“);
    }

    public void computeCentroid(Triangle t) {
        System.out.println Base::centroid\n“);
    }
}

The RightAngledTr class:

class RightAngledTr extends Triangle {
    public void draw() { 
        System.out.println(“RightAngle::draw\n“);
    }

    public void computeCentroid(RightAngled t) {
        System.out.println(RtAngle::centroid\n“);
    }
}

In my Driver program I have the following lines of code:

Triangle tr= new RightAngledTr ();
RightAngledTr rtr= new RightAngledTr ();
tr.computeCentroid(rtr);
tr.draw();
rtr.computeCentroid(tr);

The output I expected was:

Base::centroid
Base::draw
Base::centroid

However, the output I got was:

Base::centroid
RightAngle::draw
Base::centroid

My question is, why does tr.computeCentroid(rtr) call the Triangle class' method when tr.draw() calls the RightAngleTr class' method?

It doesn't make sense. Liskov substitution principle doesn't seem to apply.

Answer 1

The signatures of the computeCentroid() method are different. You are therefore not overriding, but overloading.