Page 398 - CITS - Computer Software Application -TT

COMPUTER SOFTWARE APPLICATION - CITS

10 }
Output:
Inside the Child Class

Concept of Abstract classes and methods

Data abstraction is the process of hiding certain details and showing only essential information to the user.
Abstraction can be achieved with either abstract classes or interfaces (which you will learn more about in the next
chapter).
The abstract keyword is a non-access modifier, used for classes and methods:
• Abstract class: is a restricted class that cannot be used to create objects (to access it, it must be inherited
from another class).
• Abstract method: can only be used in an abstract class, and it does not have a body. The body is provided
by the subclass (inherited from).
An abstract class can have both abstract and regular methods:
abstract class Animal {
public abstract void animalSound();
public void sleep() {

System.out.println(“Zzz”);
}
}
From the example above, it is not possible to create an object of the Animal class:

Animal myObj = new Animal(); // will generate an error
to access the abstract class, it must be inherited from another class. Let’s convert the Animal class we used in the
Polymorphism chapter to an abstract class:
Example

Get your own Java Server
// Abstract class
abstract class Animal {
// Abstract method (does not have a body)
public abstract void animalSound();

// Regular method
public void sleep() {
System.out.println(“Zzz”);
}

}
// Subclass (inherit from Animal)
class Pig extends Animal {
public void animalSound() {
// The body of animalSound() is provided here
System.out.println(“The pig says: wee wee”);

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