Basic Concepts of OO

7/29/2019 Basic Concepts of OO

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Basic Concepts of

Object Orientation

Object-Oriented Analysis

CIM2566

Bavy LI


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Basic Concepts of OO 2Prepared by: Bavy LI

What is Object-Orientation?

Object-orientation is the use ofobjects andclasses in analysis, design, and programming.

The use of objects distinguishes object-orientation from other techniques such as traditional structured methods (process-based:

data and function are separate)

knowledge based systems (logic programming:Prolog)mathematical methods (functional programming:

Scheme).


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Why did OO Arise?

Modeling in analysis and software design andlanguages for programming originally focusedon process. But many results indicated the

process approach was problematic and led tothe software crisis.

Hierarchical Functional Decomposition

Top-Down Design (TDD)

What are the advantages/disadvantages of TDD?


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Why does Organization need

Object-Orientation? Organizationally, OO provides a superior means

of: Problem/Business Analysis and Requirements

Better Software Development/Modern programmingpractice

Superior Software Engineering Metrics

Web Presence and Utilization

Software Reuse Software Use

Enterprise Engineering


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Terminology 1

OOA Object Oriented Analysisanalyzing your problem by decomposition into

objects OOD Object Oriented Designdesigning your code into objects

OOP Object Oriented Programmingprogramming using the concepts of object

orientation


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Terminology 2

Class a design (like a blueprint for a house) of an object that

contains data and methods

Object an instance (like a particular house with a street

address) of a class with a unique identity

Abstraction only exposing the important, relevant qualities of an

object or system


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Terminology 3

Attribute

a named property of an object capable of holding

state, as similar as instance variables or datamembers

Method

an operation on an object, also called a function or

operation


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What are the Primary Object-

Oriented Languages Today? C++ added classes to C as early as 1985

A hybrid object-oriented languages with powerfulfeatures including multiple inheritance, exceptions,

templates, operator overloading etc

Java was created as a simplification of C++ thatcould run on any machine, providing a write-once/run anywhere capability.

EJB 2.0 is the new standard for the J2EE, orJava 2 Platform, Enterprise Edition


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What are the Primary Object-

Oriented Methodologies Today? The Unified Modeling Language, orUML,

has become the industry standard design

and analysis notation, which lends itself toa methodology.


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What are the Benefits Of Object-

Orientation? Reuse, quality, an emphasis on modeling the

real world, a consistent OOA/OOD/OOPpackage, naturalness (our "object concept"),resistance to change, encapsulation andabstraction, and etc.

On resistance to change, system objects changeinfrequently while processes and procedures(top-down) are frequently changed.


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Big Three (and a half)

The three and a half key ingredients of

OOP are

Encapsulation,

Inheritance,

Polymorphism, and

Message Passing


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Encapsulation

hides implementation, shows only

interface

"Encapsulation is the process of hiding all of

the details of an object that do not contribute

to its essential characteristics." Booch


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Inheritance

IS A relationship

A new class can be created by "Inheriting"from another class or multiple classes.

The new class inherits methods and datamembers of the "parent" class.

This is also called "extending" the base class,or "sub-classing".


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Message Passing

a message is an invocation of a method

on an object

"an object-oriented program is a bunch of

objects laying around sending messages to

one another."


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Polymorphism

the ability to hide many different

implementations behind a single interface.

When objects respond differently to thesame message this is a form of

Polymorphism.

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Basic Concepts of OO