[转] Explain Java Encapsulation & Polymorphism & Inheritance

• Encapsulation - Hiding the implementation details of a

Class. Once a class is Encapsulated then we Cannot directly
access that class members. We can achieve encapsulation
like the following,

Eg: public class <class Name> {
private <member_1>;
private <member_2>;
}

In the above example members of the public class declared
as private. So any other class members cannot directly
access the members of that class, and those are stored as a
Single Unit. That is Encapsilation.

Real Time Example - Medical Capsule (Different medicines
packed as in single Capsule)

• Polymorphism - Ability to process an Object differently

depending upon thier Data Type or Class.

In simple words, One function - different implementations.

There two types of Polymorphism :

1) Compile time Polymorphism - The compiler know that the
way of execution of the program , means - which method
have to be invoked at compilation time. It is achieved by

Method Overloading - Same method name, may be different
parameters, may be different data type, may be different
return type. Method Overloading perform only inside of the
class.

2) Run-Time Polymorphism - The compiler doesn't know the
way of execution of the program. It will take the decision
for execute the program at Run-Time. It is achieved by

Method Overriding - Same Method name, same signatures,
similar DataType, Return type also should be the same.
Method Overriding perform at Subclass.

Real time Example - A man perform multiple role.
He is Employee of his office,He is father of his Childrens,
He is Husband of his wife, He is Son of his Parents.

• Inheritance - A class of object can inherit the properties

and methods of an another class of object. Advantage :
reusabilty of code and accessibilty of properties and
methods of derived class by subclass.

Real Time example - Father - Son Relationship.


I hope you will get idea about all those things.

If any issue let me know imm'tly.

Regards,

S.Sivadasan
Coromandel Infotech India Ltd.,
sivadasan.s@c2il.com

Chennai.