Question

Can someone explain me the execution of this program??
I know what extends keyword does. But still I’m unable to figure out what will be the result and why??

public class Maryland extends State {
    Maryland() { /* null constructor */ }
    public void printMe() { System.out.println("Read it."); }
    public static void main(String[] args) {
        Region mid = new State();
        State md = new Maryland();
        Object obj = new Place();
        Place usa = new Region();
        md.printMe();
        mid.printMe();
        ((Place) obj).printMe();
        obj = md;
        ((Maryland) obj).printMe();
        obj = usa;
        ((Place) obj).printMe();
        usa = md;
        ((Place) usa).printMe();
        }
    }

class State extends Region {
    State() { /* null constructor */ }
    public void printMe() { System.out.println("Ship it."); }
    }

    class Region extends Place {
    Region() { /* null constructor */ }
    public void printMe() { System.out.println("Box it."); }
    }

    class Place extends Object {
    Place() { /* null constructor */ }
    public void printMe() { System.out.println("Buy it."); }
}

Answer 1

Run it and you’ll see the result. What else you need?

Read it.
Ship it.
Buy it.
Read it.
Box it.
Read it.