Tutorials References Exercises Videos Menu
Create Website Get Certified Upgrade

Java Tutorial

Java HOME Java Intro Java Get Started Java Syntax Java Output Java Comments Java Variables Java Data Types Java Type Casting Java Operators Java Strings Java Math Java Booleans Java If...Else Java Switch Java While Loop Java For Loop Java Break/Continue Java Arrays

Java Methods

Java Methods Java Method Parameters Java Method Overloading Java Scope Java Recursion

Java Classes

Java OOP Java Classes/Objects Java Class Attributes Java Class Methods Java Constructors Java Modifiers Java Encapsulation Java Packages / API Java Inheritance Java Polymorphism Java Inner Classes Java Abstraction Java Interface Java Enums Java User Input Java Date Java ArrayList Java LinkedList Java HashMap Java HashSet Java Iterator Java Wrapper Classes Java Exceptions Java RegEx Java Threads Java Lambda

Java File Handling

Java Files Java Create/Write Files Java Read Files Java Delete Files

Java How To

Add Two Numbers Count Words Reverse a String

Java Reference

Java Keywords Java String Methods Java Math Methods

Java Examples

Java Examples Java Compiler Java Exercises Java Quiz Java Certificate


Java Polymorphism


Java Polymorphism

Polymorphism means "many forms", and it occurs when we have many classes that are related to each other by inheritance.

Like we specified in the previous chapter; Inheritance lets us inherit attributes and methods from another class. Polymorphism uses those methods to perform different tasks. This allows us to perform a single action in different ways.

For example, think of a superclass called Animal that has a method called animalSound(). Subclasses of Animals could be Pigs, Cats, Dogs, Birds - And they also have their own implementation of an animal sound (the pig oinks, and the cat meows, etc.):

Example

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

class Pig extends Animal {
  public void animalSound() {
    System.out.println("The pig says: wee wee");
  }
}

class Dog extends Animal {
  public void animalSound() {
    System.out.println("The dog says: bow wow");
  }
}

Remember from the Inheritance chapter that we use the extends keyword to inherit from a class.

Now we can create Pig and Dog objects and call the animalSound() method on both of them:

Example

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

class Pig extends Animal {
  public void animalSound() {
    System.out.println("The pig says: wee wee");
  }
}

class Dog extends Animal {
  public void animalSound() {
    System.out.println("The dog says: bow wow");
  }
}

class Main {
  public static void main(String[] args) {
    Animal myAnimal = new Animal();  // Create a Animal object
    Animal myPig = new Pig();  // Create a Pig object
    Animal myDog = new Dog();  // Create a Dog object
    myAnimal.animalSound();
    myPig.animalSound();
    myDog.animalSound();
  }
}

Try it Yourself »

Why And When To Use "Inheritance" and "Polymorphism"?

- It is useful for code reusability: reuse attributes and methods of an existing class when you create a new class.