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COMPUTER SOFTWARE APPLICATION - CITS

Polymorphism in Java

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

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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”);
}

}

Creating, Implementing And Extending Interfaces

An interface in Java is syntactically similar to a class but can have only abstract methods declaration and constants
as members.

In other words, an interface is a collection of abstract methods and constants (i.e. static and final fields). It is used
to achieve complete abstraction.
Every interface in Java is abstract by default. So, it is not compulsory to write abstract keyword with an interface.
Once an interface is defined, we can create any number of separate classes and can provide their own
implementation for all the abstract methods defined by an interface.
A class that implements an interface is called implementation class. A class can implement any number of
interfaces in Java. Every implementation class can have its own implementation for abstract methods specified in
the interface as shown in the below figure

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CITS : IT&ITES - Computer Software Application - Lesson 109 - 115 CITS : IT&ITES - Computer Software Application - Lesson 109 - 115