Definition

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Full form of OOPS is Object Oriented Programming Structure/System.It is a programming system which is based on concept of objects.Each of these objects are used to perform specific actions

It is also said to be a programming paradigm methodology,here programming paradigm means a method to solve problems using programming language.So OOP is a method which use object to write programs and solve problems.

There are 6 main concept or we can say pillars of OOPS,these are:-

Let us understand each concept one by one in detail.

Object

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It is defined as a real life entity,whatever we see in real life is termed as an object.These entities have some properties and task to perform.It is a basic unit of object-Oriented Programming language.



An object is also said to an instance of class,that is ,it will follow all the prototype defined by the class.There can be mutliple instance of a class in a program.

An object consists of:-

1. unique Identity:Each object has unique Identity,that enable object to interact with other objects
2. Behavior: It tells what object does.It can be used a response for one object to other objects
3. State/Properties/Attributes: It tells how the object will look like.

Let us understand this real-life entity by an example:-

In implementing this real-world object in software form,all these Attributes are represented through data items known as member variables and Behavior are represented through methods known as member methods.

Classes

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A class is one of the basic concepts of OOPS,it is the collection of objects.Without a class object is nothing.

A class is declared by use of the class keyword. The class body is enclosed between curly braces { and }. The data or variables, defined within a class are called instance variables.The code is contained within methods of a class.

It has some properties and tasks,and each object must follow these prototypes defined in the class.

Let us understand this by example



From the above example,we can observe that each objects named as agam and raman,follow attributes of a class such as name,roll number,joining data and methods of a class such as read(),write().

Syntax :

From the above syntax we can say that "Class is a collection of data and methods."

Example : If we have to build a building then we require a structure por blueprint to build it. So this building is an object and that blueprint is a class.
So to define object what object knows and what object does we use class.

Polymorphism

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If a function behaves differntly for different objects then this is known as polymorphism.It is one of the OOPs concept in java in which methods and variables can have different forms.

Function overloading is an example of polymorphism.

Let us discuss about method overloading defination and example given below

Method Overloading

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The functions having the same name but have different numbers of parameters passed to it, which can have different data types like int, double, float and used to return different values are known as overloaded method. This process is known as function overloading

Consider the above two declarations :

The above mentioned two methods have the same name but different parameter declaration if you call min() with int parameter then min() method that expects int parameter will be invoked and if you call min() with double parameters the min() method that expects double parameters will be invoked. This referred to as method overloading and method min() is said to be overloaded

Encapsulation

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Encapsulation in Java is wrapping the data (variables) and code acting on data (method) together as a single unit.

Real world example of encapsulation :

Steps to achieve Encapsulation

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• Declare the variable of a class as private


• Provide public setter and getter methods to modify and view the variable values.

In encapsulation the variables of a class (data) will be hidden from other classes and can be accessed only through the methods of their current class. This method is called data hiding

Abstraction

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It is one of the OOPs concept in which we show only essential parts and hide the implementiion details.The non-essential parts are not displayed to the users.

Let us understand this by an example:

The above example is of ATM machine.In an ATM machine,we peform function like withdraw cash,deposit cash,check balance,print bills,and so on.Since it performs a lot of actions,it doesn’t show us the process. It hiddes its process by showing only the main things like getting inputs and giving the output.

Inheritance

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It is one of the OOPs concept in which we acquire the properties of one class to another class.

It has one parent class known as base class and can have more than one child class which is known as derived class,and Inheritance allows child classes to inherit properties from parent class.

Let us understand by an example:-

In the above example here animal class is a parent class,and these dog class,cow class and cat class are child classes which are derived from animal class,and these child classes inherit some common properties and Behavior from animal class.