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by PRO FE S S OR

E N C A P S U L A T I O N

AN OBJECT-ORIENTED PILLAR

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In Object-Oriented Language, ENCAPSULATION refers to part of a program that is written within a block that has a boundary, and contains:

procedures, functions or sub-routines (methods) as well as

attributes (variables).

In Object-Oriented language that block is represented by a class.

A class in Java encapsulates methods and attributes.

Global variables as known in other languages do not exist in Object-Oriented Programming. Variables are contained withint its own class. By the same token, there are no global methods in Object-Oriented languages. All variables and methods are all encapsulated within a class.

So we can then say that Encapsulation allows any class to contain methods and attributes that can only be used within the class, or accessed by instances (Objects) of that class.

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Why ENCAPSULATION ?

You probably wonder if we don't have Global Variables, how can a variable can be used or accessed if it's outside its class. An Object which is an instance of a class may refer to variables or objects of another class, and this is what we know as coupling. In Object-oriented language, a high coupling is not desirable. De-coupling then becomes a goal when programming. Keeping the separation among objects when all possible is an ideal situation.

By encapsulating the program into classes it's easier to keep this separation (de-coupling) among objects and that's why is the most important feature in Object-Oriented Programming.

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Example of JAVA class showing Encapsulation:

class Capsule
{ // beginning of class

double kms;
private final double factor=1.6;
void convert(double tmpMiles)
{
kms = tmpMiles*factor;
} } // ending of class

// The Capsule class above uses curly braces for its beginning and ending bounds.
// Attributes "kms" and "factor" and method "convert" are within the class. (Encapsulation)