Test Classes in Java

Question

I have an assignment that looks like this:

Write a class called Animal with a default sound() method. Create child classes with the sound() method for the following animals:pig, sheep, duck, cow.

Create another class called AnimalTest that reads the command line user input and creates the appropriate Animal child class based on the type of animal, and then calls the animal’s sound() method. Take some time to reflect on which class to create.

Do I write a test class that creates Animal child classes? How do you create animal classes from the Test Class? YouTube isn't too helpful on this.

This is my code:

PARENT CLASS

public class Animal {
    void animal() {
        System.out.println("I am an animal");
    }
    public void sound() {
        System.out.println("An animal makes a sound based on the animal that it is.");
    }
    
    public static void main(String[] args) {
        Animal mypig = new Animal();
        mypig.sound();
    }
}

ONE OF FOUR CHILD CLASSES (others basically repeats)

public class cow extends Animal{
    public cow() {
        System.out.println("I am a cow");
    }
    public void sound() {
        System.out.println("cow says “moo”");
    }
}

MAIN CLASS

public class Main {
    pig p = new pig();
    sheep s = new sheep();
    duck d = new duck();
    cow c = new cow();
}

ANIMAL TEST CLASS

import java.util.Scanner;

public class AnimalTest {
    
    //create main class
    public static void main(String[] args) {
        
        //create scanner
        Scanner scan = new Scanner(System.in);

        //get scanner input
        String input = scan.nextLine(); 
    }
}

I tried looking for test classes on YouTube but existing videos were only showing how to test existing classes.

Answer 1

AnimalTest is just a name your professor recommmended for the class that holds the main method (I believe there might have been some confusion, as you might have thought it was a special class type).

So, your Animal Test class should look something like this:

import java.util.Scanner;

public class AnimalTest{
    public static void main(String[] args) {
        Animal animal = null; // create an animal object
        Scanner scanner = new Scanner(System.in);
        String input = scanner.nextLine();
        if(input.equals("pig")){ // assign a specific object instance based on the input
            animal = new Pig();
        }else if(input.equals("sheep")){
            animal = new Sheep();
        }else if(input.equals("cow")){
            animal = new Cow();
        }            
        animal.sound();       
    }
}

Your Animal class only needs the sound() method, which will be overrider by the child clases

class Animal {
    void sound(){
        System.out.println("Animal Sound");
    }    
}

Finally, your animal child classes should appear as follows (The @Override is an java annotation utilized when replacing method implementation from parent clases).

class Pig extends Animal{
    @Override
    void sound (){
        System.out.println("Pig says oink !!");
    }
}

If you found this answer useful, consider marking it as the accepted answer. Good luck.