This programming style makes me dizzy

Computer Science Level 3

What is the output of this Java program?

import java.util.*;
import java.lang.*;
import java.io.*;


class Mammal{ 
    void eat(Mammal m){
        System.out.println("Mammal eats food");
        }
    } 
class Cattle extends Mammal{
    void eat(Cattle c){
        System.out.println("Cattle eats hay"); 
        } 
    }
class Horse extends Cattle{
    void eat(Horse h){
        System.out.println("Horse eats hay"); 
        } 
    } 

public class Main{
    public static void main(String[] args){ 
        Mammal h = new Horse();
        Cattle c = new Horse(); 
        c.eat(h); 
        }
    }

I am not a Java person myself. A friend sent me this. You could help him by adding a solution.

Mammal eats food Cattle eats hay Horse eats hay

1 solution

Stojan Samojlovski
Sep 2, 2016

So the first is $Mammal$ reference that points to some instance of $Horse$ object.That means that first object named ('h') can access the method in class $Horse$ when ever it is called but still refer to $Mammal$ .
The second declaration is where $Cattle$ reference points to some instance of $Horse$ object. That means simply like in the first , that object named ('c') can access the method from class $Horse$ if it is called.
So in the example we have call from object reference $Cattle$ where the method has as it's argument reference of class $Mammal$ .
By the concept of inheritance when some class $B$ extends from some class $A$ , class $B$ can access all public and protected members and methods.
In our example the second object named ('c') must call the method which has as argument reference of class $Mammal$ and it also extends all methods which are public from that class (in our example it inherits the method $eat()$ where the argument is reference from class $Mammal$ and that method is in class $Mammal$ ) therefore output must be: "Mammal eats food" .

Thanks! I will send this solution to my friend

Agnishom Chattopadhyay - 4 years, 9 months ago

Keep me updated for his response.

Stojan Samojlovski - 4 years, 9 months ago

This programming style makes me dizzy

1 solution

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