Encapsulation and Abstraction ppt

Encapsulation and

Abstraction

Chapter 4

Objects contain data and methods to send and

receive messages. Data members of objects can have

a different scope or visibility. You use access

specifier to define the scope of data member and

method.

This chapter introduces the concept of abstraction

and encapsulation. It discusses the implementation

of encapsulation by using access specifiers. It also

explains the concept of using methods. In addition,

the chapter also discusses the static variables and

static functions.

In this chapter, you will learn to:

 Define abstraction and encapsulation

 Implement encapsulation by using access

specifiers

 Use methods

 Use static variables and static functions

Objectives

¤NIIT Encapsulation and Abstraction 4.3

Abstraction and encapsulation are important features of any OOPs language. Abstraction

involves extracting only the relevant information. Encapsulation involves packaging one

or more components together.

Consider the following example:

An automobile salesperson is aware that different people have different preferences.

Some people are interested in the speed of a car, some in its price, some in the engine, and

the some in its style. Although all of them want to buy a car, each of them is interested in

a specific attribute or feature. The salesman knows all the details of a car, but he presents

only the relevant information to a potential customer. As a result, the salesman practices

abstraction and presents only relevant details to customer.

In other words, abstraction means ‘looking for what you want’ in an object or a class.

Consider abstraction from the perspective of a programmer who wants a user to be able to

add items to a list. However, the detail of how a particular task in a program is

accomplished is hidden. Abstraction does not mean that information is unavailable. It

means that all the information exists, but only the relevant information is provided to the

user.

Encapsulation literally means ‘to enclose in or as if in a capsule’. Encapsulation is defined

as the process of enclosing one or more items within a physical or logical package. It

involves preventing access to nonessential details.

For example, when you plug in the cord of the vacuum cleaner and turn on the switch, the

vacuum cleaner starts. You do not see the complex processes needed to actually convert

electricity into suction power. In other words, the exact working of the cleaner has been

encapsulated. Therefore, encapsulation is also explained as information hiding or data

hiding because it involves hiding many of the important details of an object from the user.

Abstraction and encapsulation are different but related features. Abstraction enables you

to make the relevant information visible. Encapsulation enables you to package

information to implement the desired level of abstraction. Therefore, encapsulation assists

abstraction by providing a means of suppressing the nonessential details. Encapsulation

allows some information to be hidden but it also allows some information to be visible.

Introducing Abstraction and Encapsulation

Defining Abstraction

Defining Encapsulation