Introduction to Object Oriented Programming (OOP) ~ A2Z Computer

Class

A class is a user defined blueprint or prototype from which objects are created. It represents the set of properties or methods that are common to all objects of one type.

Object

It is a basic unit of Object Oriented Programming and represents the real life entities. A typical Java program creates many objects, which as you know, interact by invoking methods. An object consists of :

State : It is represented by attributes of an object. It also reflects the properties of an object.
Behavior : It is represented by methods of an object. It also reflects the response of an object with other objects.

Let us consider an example of real world class to understand the way different characteristics and common behaviours are embedded in its objects.

The syntax to create an object in Java:

ClassName ObjectName = new ClassName();

How to create objects of the above mentioned class?

Object 1:

TelevisionSet objSony = new TelevisionSet();

Object 2:

TelevisionSet objLG = new TelevisionSet();

Let us take an example to understand as how software class and objects will be used for programming purpose.

In the structure shown above, the class ‘Rectangle’ is designed with the data members (i.e. states or attributes) – ‘length and breadth’ and member functions –‘input(), calculate() and display()’. The objects can be created as shown below:

Object 1

Rectangle Area = new Rectangle();

Object 2

Rectangle Perimeter = new Rectangle();

The structure shown above, states when the objects Area and Perimeter are created then each object will automatically possess the data members and member function described within the class Rectangle. The allocation of data members pertaining to each object can be different but the function to be carried on them will be common.

Hence,

Area.input() : will accept length and breadth of object Area

Area.calculate () : will perform calculations by using length and breadth of object Area.

Area.display() : will display the result of calculation of object Area.

Similarly, we can show the above tasks for the object Perimeter.

Principles of Object Oriented Programming (OOP)

1) Data Abstraction

The ‘Data Abstraction’ is defined as an act of representing the essential features without knowing background details.

2) Encapsulation

Wrapping of data and functions of an object as a unit that can be used together in a specific operation is known as ‘Encapsulation’.

3) Inheritance

Inheritance is the process in which objects of one class can link and share some common properties from the objects of another class.

4) Polymorphism

Polymorphism is the process of using a function for more than one purpose. It allows the use of different internal structures of the objects by keeping the same external interface.

The advantages of OOP

· Data values are secured.

· Mishandling of data is protected.

· Error detection and correction become easier.

· Easier in coding complex programs.

Some examples of OOP

Java, C++, Small Talk, Eiffel, Python are some of the Object Oriented Programming Languages.

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