Question

Define an interface FarmAnimal that contains two methods: getName() and talk(), each returns a string. Declare an abstract class FarmAnimalBase that implements the interface FarmAnimal. In the class FarmAnimalBase, define a private final instance variable name (type: String), a public constructor that initializes the value of the instance variable name, and a public method getName() that returns the value of the instance variable name. Note that we do not implement the method talk() declared in the interface FarmAnimal, that’s the very reason we have to declare the class FarmAnimalBase as an abstract class. Make three classes, Cat, Dog, and Cow, that inherit from FarmAnimalBase. Each of the inherited classes has a constructor that initializes the value of the instance variable. Each of the inherited classes also implements a method (prototype: public String talk();), which contains only one line of code. For class Cat, return "Meow! Meow!"; for class Dog, return "Arf! Arf!"; and for class Cow, return "Moo! Moo!";

Supply a test program FarmAnimalTest that tests these classes and methods. Specifically, create three objects, one each from the classes Cat, Dog, and Cow using the names - "Missy", "Lassy", and "Nossy". Then put all these three objects into an ArrayList<FarmAnimal> farmAnimals of FarmAnimal objects. And finally, show the farm animal names and sounds they make. The output should look exactly like the following:

Missy: Meow! Meow! Lassy: Arf! Arf! Nossy: Moo! Moo!

Submit all six source code files: FarmAnimal.java, FarmAnimalBase.java, Cat.java, Dog.java, Cow.java, and FarmAnimalTest.java

Answer 1

All the required files are given below in their respective tables.

FarmAnimal.java

public interface FarmAnimal {       public String getName();    public String talk(); }

FarmAnimalBase.java

public abstract class FarmAnimalBase implements FarmAnimal{       private String name;       public FarmAnimalBase(String name)    {        this.name = name;    }       @Override    public String getName()    {        return name;    }       }

Cat.java

public class Cat extends FarmAnimalBase {       public Cat(String name)    {        super(name);    }    @Override    public String talk() {               return "Meow! Meow!";    } }

Dog.java

public class Dog extends FarmAnimalBase{    public Dog(String name)    {        super(name);    }    @Override    public String talk() {        return "Arf! Arf!";    } }

Cow.java

public class Cow extends FarmAnimalBase{    public Cow(String name)    {        super(name);    }    @Override    public String talk() {        return "Moo! Moo!";    }       }

FarmAnimalTest.java

import java.util.ArrayList; public class FarmAnimalTest {       public static void main(String[] args)    {        FarmAnimalBase cat = new Cat("Missy");        FarmAnimalBase dog = new Dog("Lassy");        FarmAnimalBase cow = new Cow("Nossy");               ArrayList<FarmAnimal> farmAnimals = new ArrayList<FarmAnimal>();        farmAnimals.add(cat);        farmAnimals.add(dog);        farmAnimals.add(cow);               for(FarmAnimal animal : farmAnimals)        {            System.out.println(animal.getName() + ": " + animal.talk());        }    } }

OUTPUT