Sunday, February 22, 2015

Objection Orientation: Polymorphism, Abstraction, Encapsulation, and Inheritance

Developers who are new to object-oriented programming often struggle to understand the long-winded explanations that are scattered across the interwebs.  The intent of this post is to ease the pain (hopefully) by summarizing the main concepts of object orientation in a concise and precise format by providing a definition, two examples, and a brief explanation of its benefits.

Polymorphism

Definition:  Polymorphism is the concept where a parent type can have many sub-types.

Example #1:  ArrayList and LinkedList are sub-types of the parent type List.

Example #2:  Car, Motorcyle, and Bus are sub-types of the parent type Vehicle.

Benefits:  Polymorphism allows you to use a single parent type to interact with all possible sub-types.  It also helps to decouple your code.  When you are working with a List object, you can freely swap out the underlying implementation from an ArrayList to a LinkedList and vice-versa.

Abstraction

Definition:  Abstraction is the generalization of common functionality across different objects.

Example #1:  List is an abstraction of ArrayList and LinkedList because it generalizes the common functionality of adding and removing elements.

Example #2:  Vehicle is an abstraction of Car, Motorcyle, and Bus because it generalizes the common functionality of accelerating and braking.

Benefits:  Abstraction allows you to interact with different objects via a common interface.

Encapsulation

Definition:  Encapsulation is the packing (hiding) of data and implementation details into a class or function.

Example #1:  Data and implementation details about a car are encapsulated (packed, hidden) into a Car class.  Access to its data can be controlled via public, protected, and private modifiers.

Example #2:  The functionality to accelerate and brake a car is encapsulated (packed, hidden) into functions.  Access to these functions can be controlled via public, protected, and private modifiers.

Benefits:  Encapsulation allows you to hide implementation details and protect against mis-use by other classes.  It also helps to decouple your code.  For example, I could modify the formula in the accelerate function without breaking any code dependencies on that function.

Inheritance

Definition:  Inheritance is the re-use of a base class's functionality by a sub-class.

Example #1:  Car is a sub-class that inherits the functionality of its base class Vehicle, including the data (currentHeading, velocity, weight) and functions (turn, accelerate, brake).

Example #2:  A Car can turn because it inherited the functionality from its base class Vehicle.

Benefits:  Inheritance allows you to re-use functionality and reduce duplicate code.

Polymorphism, abstraction, encapsulation, and inheritance are distinctly different concepts, but together they support the paradigm of object orientation.  I hope this post cleared up any misunderstandings of these four pillars object orientation!

1 comment:


  1. Once extensive comprehensive extensive wide range has used an company, it will end and quit and trend trader software efficiency. Therefore, any extensive comprehensive extensive wide range can only be used once. Business accessibility rules like stop-loss or take-profit levels, accessibility lot size and falling can be pre-specified before business is used.

    ReplyDelete