Question

*Code in Java*

Write a Java program called to demonstrate Inheritance and Polymorphism

1. Create a base class called Person, that has fields, constructors, and anything else you think you may need as you go along. It should also have a method called speak(), to make the person say their name (using System.out.println)
2. Create any two subclasses of the Person class. Each subclass must have the following:
   • At least one new field, with getter/setter methods
   • A default constructor that sets its fields to default values, and also all the fields of it's base class to default values
   • A parameterized constructor that accepts all fields from both the base (Person) and new subclass fields
   • A speak method, that says something specific that an object of that class would say. (make it up)
3. In a main method, create a Person object, and one object of each subclass (2 objects), and stick all 3 objects in either an ArrayList or an array. Then just loop through (iterate) the ArrayList or array, and call the speak method for each object  

Answer 1

import java.util.*;

class Person

{

    private String name;

    private int age;

   

    // constructor

    Person()

    {

        this.name = "";

        this.age = 0;

    }

   

    // constructor

    Person(String name, int age)

    {

        this.name = name;

        this.age = age;

    }

   

    // setter method

    public void setName(String name)

    {

        this.name = name;

    }

   

    public void setAge(int age)

    {

        this.age = age;

    }

   

    // getter method

    public String getName()

    {

        return this.name;

    }

   

    public int getAge()

    {

        return this.age;

    }

   

    // to make the person say their name (using System.out.println)

    public void speak()

    {

        System.out.println("My name is " + this.getName());

    }

}

class Dog extends Person

{

    private String type;

    private String voice;

   

    Dog()

    {

        // call the constructor of parent class

        super();

       

        this.type = "Dog";

        this.voice = "";

    }

   

    Dog(String name, int age, String voice)

    {

        // call the constructor of parent class

        super(name, age);

       

        this.type = "Dog";

        this.voice = voice;

    }

   

    // setter method

    public void setVoice(String voice)

    {

        this.voice = voice;

    }

   

    // getter method

    public String getVoice()

    {

        return this.voice;

    }

}

class Cat extends Person

{

    private String type;

    private String voice;

   

    Cat()

    {

        // call the constructor of parent class

        super();

       

        this.type = "Cat";

        this.voice = "";

    }

   

    Cat(String name, int age, String voice)

    {

        // call the constructor of parent class

        super(name, age);

        

        this.type = "Cat";

        this.voice = voice;

    }

   

    // setter method

    public void setVoice(String voice)

    {

        this.voice = voice;

    }

   

    // getter method

    public String getVoice()

    {

        return this.voice;

    }

}

public class Test

{

    public static void main(String[] args)

    {

        ArrayList<Person> arr = new ArrayList<Person>();

       

        arr.add( new Person("Chandler Bing", 35) );

        arr.add( new Dog("Rocky", 11, "Woof") );

        arr.add( new Cat("Tinker", 12, "Meow") );

       

        // traverse the ArrayList

        for( Person ob : arr )

            ob.speak();

    }

}

Sample Output