Features of object oriented programming language

In Object Oriented Programming program or an application is divided and organised using the objects. Objects are the parts of a program using which we organise different tasks that are meant to be achieved by the application. In OOP several modules and task are again organised using the objects.

Objects are integral part of any object oriented programming languages and as Java is OOP language it fully supports the concept of objects. But there are some other features of OOP.

Features of Object Oriented Programming (JAVA)

Any language which is object oriented has following set of features including Java:

1.     Abstraction: Abstraction means releasing only essential and useful features and hiding other unwanted feature or internal implementation. Abstraction is not a practical phenomenon but it is a purely logical concept. In OOP the phenomenon of Abstraction is achieved through the use of encapsulation, yet another feature of OOP.

Ex: To understand the concept of Abstraction let’s take an example of calculator. You are not aware of the internal implementation of calculator but still you can perform all the calculations required by and which are supported by the calculator. In this all the internal implementation or unnecessary details which are not required and are not meant to be for user are hidden but all the essential features only of calculations are exposed to user.

2.      Encapsulation: Encapsulation means the wrapping of internal implementation which includes functionality and data, as single unit. In Java one of the members of Java programming language ‘class’ is used to encapsulate the internal implementation (data and functionality).

3.      Polymorphism:  Polymorphism means performing multiple tasks of same type with same name. Polymorphism allows us to use the already written method more than once and thus decreases maintenance overhead.

Ex:  In a program of calculation area of different shapes like square, rectangle, circle etc we can use method with name as ‘CalculateArea’.

4.     Inheritance: Inheritance is the process by which we can reuse the features implemented in one class, for another class. By implementation we can reduce the number of lines in our code so it avoids time and maintenance problem also.

Ex: In a specific application we can define one class as ‘User’ and we can extend the features of this class to other class like ‘NormalUser’, ‘Editor’, ‘Administrator’ etc. Here some of the features like username and password can be extended newly defined classes like ‘NormalUser’, ‘Editor’, ‘Administrator’. In this case class ‘User’ is called as parent class and other newly defined classes which are inheriting the features of this class are called as child classes.

5.     Class: Class is very important concept in Java. Class acts as blue print for the object. It provides the structure and other support for the object. By using the structure defined in class we can define new members of the class which are called as objects. Class serve as data type for the object as keyword ‘int’ serve as data type for 10 or any other integer value. The class is defined type in Java and it is not available in other OOP languages.

In Java java.lang.Object will be parent for other classes by default.

How to define a class in java?

Like any other programming language java also has specific syntax to declare each member of Java programming language. So the syntax for declaring a class in java is:

[Modifier(s)] class [extends] implements[interface(s)]

6.     Object: An object is instance of class. We can create as many instances as we want (specifically required by application). Object is used to instantiate the class; without object class is nothing in a real application. We create reference in memory to store the entities which are defined in class. Thus class provides structure to create an entity and an object represents that particular entity in memory and in real time. Object has state and behaviour.

How to create an Object in java?

The syntax to create object in Java is:

=new

OR

new

In above declaration syntax the first represents the class for which we are going to create the object.

represents reference variable using which

 The new object will be stored in memory and it can be used to later to reference the object in different contexts.

Ex: This example shows how to create and class and object in Java:

Class  Human{             //This statement in Java is responsible for creating a class.

String name;

String nationality;

String gender;

int age;

}

Human h1=new Human();      //This statement in Java is responsible for creating a object of class Human.

So in above example we have just declares the class and created new member of or instance of class which will be represented by reference h1 in later part of the program. The ‘new’ keyword in above code snippet is defined keyword in Java and is used to create instances of class or a new object. This is not a complete Java program and this program just aims to provide you insight to the Object and class and how object and class are created in Java.

There some rules that every programmer should follow while writing the class and objects in java; but we will see those rules in later parts.