Introduction to Object Oriented Programming Language

With the improvement in technology, the trends of programming languages have shifted towards the Object Oriented Programming(OOP). Here I tried to explain classes and Objects in java.

Object oriented programming means any kind of programming language which uses some object oriented concepts. In OOP, programmer not only define the data types of data structure but also the functions to be performed. In this way, data structure becomes an object which includes data and function. Examples of Object oriented languages are C++, Java etc.

Main concepts of OOP

Some of the main concepts of Object Oriented Programming are:

1.    Classes

2.    Data Abstraction

3.    Information Hiding

4.    Inheritance

5.    Polymorphism

6.    Encapsulation

Java classes

I will explain the concept of classes in java here. A class is a blueprint or prototype from which objects are created. This section defines a class that models the state and behavior of a real-world object. It intentionally focuses on the basics, showing how even a simple class can cleanly model state and behavior. A class contain data members and functions. A class defines all the common properties of object that belong to it.

Example of class in java

For example you want to write a class of car in java. As I stated earlier class is simply a prototype of real world object. So first think about the car for which you have to write a class.

A car has some properties, like car is of red color, car has some price and other in the same way. These properties are data members for which you have to write functions or operations or some action of real world. Like if you want to know car color, you have to write a function which will return color of the cars. That's it. Here a sample of class is given below:

public class car{

String color;

double price;

String model;

String getCarColor(){

}

double getCarPrice(){

}

}

 Defining a class

Variable types in a class

A class can contain any of the following variable types.

• Local variables: Variables defined inside methods, constructors or blocks are called local variables. The variable will be declared and initialized within the method and the variable will be destroyed when the method has completed.
• Instance variables: Instance variables are variables within a class but outside any method. These variables are initialized when the class is instantiated. Instance variables can be accessed from inside any method, constructor or blocks of that particular class.
• Class variables: Class variables are variables declared with in a class, outside any method, with the static keyword.

A class can have any number of methods to access the value of various kinds of methods. In the above example, barking(), hungry() and sleeping() are methods.