Understanding OOP Concepts: OOP, Class & Object

In this article, I’m going to talk about OPP, Class & Object. OOP provides a clear modular structure for programs. Let’s try to get the basic idea:

Table of Contents

  1. What is OOP?
  2. Understanding Class
  3. Understanding Object
  4. Example in Java
  5. Example in PHP

What is OOP?

Object-oriented programming is a programming methodology constructed around objects. OOP is associated with concepts such as class, object, Inheritance, Encapsulation, Abstraction, Polymorphism etc.

Figure 1: Concepts of OOP

Before going to understand class & object, let’s have a look at the following figure:

Figure 2: Image is taken from javatutorial.net

Understanding Class

Class is a blueprint or template that defines the data and behavior of a type. It is a collection of properties and methods.

According to Figure 2, Car is a class. In the Car class, we may define the car brand, model etc. These are called properties/states/attributes. We’ll learn more about properties in the next article.

Note: When a class is defined, no memory is allocated.

Understanding Object

An object can be considered as an instance of a Class. It is a bundle of some characteristics and behavior.

According to Figure 2,  Audi is an object of the Car class.

Note: When an object is created, memory is allocated.

Example in Java

This is the Car class in Java:

public class Car {
  // properties, methods, etc.

and this is the object of Car:

Car audi = new Car();

Example in PHP

Let’s write the Car class and Audi object in PHP:

// class
class Car {
  // properties, methods, etc.

// object
$audi = new Car ();

I’ll explain the properties and methods in the next article in detail.

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Md Obydullah is a software engineer and full stack developer specialist at Laravel, Django, Vue.js, Node.js, Android, Linux Server, and Ethichal Hacking.