Java Polymorphism Programming - Animal Class with Bird and Cat Subclasses for Specific Sounds

Java Polymorphism: Exercise-1 with Solution

Write a Java program to create a base class Animal (Animal Family) with a method called Sound(). Create two subclasses Bird and Cat. Override the Sound() method in each subclass to make a specific sound for each animal.

In the given exercise, here is a simple diagram illustrating polymorphism implementation:

Polymorphism: Animal Class with Bird and Cat Subclasses for Specific Sounds

In the above diagram, we have a base class Animal with the makeSound() method. It serves as the superclass for two subclasses, Bird and Cat. Both subclasses override the makeSound() method to provide their own sound implementations.

Sample Solution:

Java Code:

// Animal.java
// Base class Animal

public class Animal {
    public void makeSound() {
        System.out.println("The animal makes a sound");

// Bird.java
// Subclass Bird

public class Bird extends Animal {
    public void makeSound() {
        System.out.println("The bird chirps");
// Cat.java
// Subclass Cat

public class Cat extends Animal {
    public void makeSound() {
        System.out.println("The cat meows");
// Main.java
// Main class

public class Main {
    public static void main(String[] args) {
        Animal animal = new Animal();
        Bird bird = new Bird();
        Cat cat = new Cat();

        animal.makeSound(); // Output: The animal makes a sound
        bird.makeSound();   // Output: The bird chirps
        cat.makeSound();    // Output: The cat meows

Sample Output:

The animal makes a sound
The bird chirps
The cat meows


Flowchart: Base class Animal
Flowchart: Subclass Bird
Flowchart: Subclass Cat
Flowchart: Main class

Java Code Editor:

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Java: Tips of the Day

Hashset vs Treeset:

HashSet is much faster than TreeSet (constant-time versus log-time for most operations like add, remove and contains) but offers no ordering guarantees like TreeSet.


  • the class offers constant time performance for the basic operations (add, remove, contains and size).
  • it does not guarantee that the order of elements will remain constant over time
  • iteration performance depends on the initial capacity and the load factor of the HashSet.
  • It's quite safe to accept default load factor but you may want to specify an initial capacity that's about twice the size to which you expect the set to grow.


  • guarantees log(n) time cost for the basic operations (add, remove and contains)
  • guarantees that elements of set will be sorted (ascending, natural, or the one specified by you via its constructor) (implements SortedSet)
  • doesn't offer any tuning parameters for iteration performance
  • offers a few handy methods to deal with the ordered set like first(), last(), headSet(), and tailSet() etc

Important points:

  • Both guarantee duplicate-free collection of elements
  • It is generally faster to add elements to the HashSet and then convert the collection to a TreeSet for a duplicate-free sorted traversal.
  • None of these implementations are synchronized. That is if multiple threads access a set concurrently, and at least one of the threads modifies the set, it must be synchronized externally.
  • LinkedHashSet is in some sense intermediate between HashSet and TreeSet. Implemented as a hash table with a linked list running through it, however,it provides insertion-ordered iteration which is not same as sorted traversal guaranteed by TreeSet.

So a choice of usage depends entirely on your needs but I feel that even if you need an ordered collection then you should still prefer HashSet to create the Set and then convert it into TreeSet.

  • e.g. SortedSet<String> s = new TreeSet<String>(hashSet);

Ref: https://bit.ly/3d3waGh


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