OOP

OOPs stands for Object oriented  Programming. Previously we used to follow the procedural programming paradigm while developing the software which makes it hard to add the new functionality at  the maintenance phases. Even it was harder to test the module in the procedurally developed code because the coded modules were so tightly coupled. Even there was not even any chance to reuse the existing modules to decrease the coding efforts. Then there came the concept of the 

Object Oriented Programming which was totally based on the real life entities and scenerios. OOPs enables to program the real world objects and easily play with them in our application development scenerios. OOPs focuses on the relevant data of the real world object and forces to concentrate on the various functionalities effecting the states of the data. 

OOPs revolve around the four concepts:
1. Encapsulation
2. Polymorphism
3. Abstraction
4. Inheritance

In OOPs, these concepts are implemented through a class definition and achieved through the object creation process, programmatically.

Read more at :

www.roseindia.net/java/beginners/oop-in-java.shtml