ITP OO Concepts

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Object Oriented Concepts



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Objective

At the end of this session, you will be able to:

Introduce Object Oriented Programming

Identify Objects

Design Classes

Understand Object Oriented Concepts

Abstraction

Encapsulation

Inheritance Polymorphism




Agenda

Need of Object Oriented Programming

Object

Class

Abstraction

Encapsulation

Inheritance

Polymorphism




Introduction

Methodology used for programming is called asProgramming Paradigm

Two Programming Paradigms

Procedure Oriented Programming

Decide which modules you want; partition the program so thatdata is hidden in modules

Importance is given to algorithm rather than data

Object Oriented Programming (OOP) Decide which types you want; provide a full set of operations for

each type

Importance is given to data (Objects) & algorithm supports thedata



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Need of OOP

Procedural ProgrammingLanguages Object Oriented Languages

The unit is a function The unit is a class

Importance is given to the sequenceof tasks to be done

Importance is given to the data.

Larger programs are divided intofunctions

Larger programs are divided intoobjects.

Most functions share global data Mostly the data is private and onlyfunctions inside the object canaccess the data.

Follows a top down approach inproblem solving

Follows a bottom up approach.




Need of OOP (Contd«)

World is made up of objects!

Orders

Manufactures

Ship via

ClientManufacturer

Product

Airplane

Truck

Purchasing a product




Need of OOP (Contd«)

Object Oriented Programming is an easy way of transforming real world problem into software

Fundamental knowledge of object oriented concepts isnecessary to adopt Object Oriented Programming paradigmfor software




Object Oriented Concepts

Abstraction

Encapsulation

Inheritance

Polymorphism




Object

An object represents an entity, either physical or conceptual

Every entity in the world is an object

Object has:

State

Behaviour

Identity

Truck

Paragraph

Linked ListData Structure

Physical Entity

Conceptual Entity

Conceptual Entity (Programatic)




Object Characteristics - State

The state of an object is one of the possible conditions inwhich an object may exist

The state of an object changes by Behavior

Represented by specific values for attributes

A. B. Chowbe

Name

Employee No

Date of joining

Status

A. B. Chowbe

10000

04/01/2006

Teaching

Object Object State




Object Characteristics - Behavior

Behavior determines how an object responds to requestsfrom other objects

Behavior is represented by the set of messages it canrespond to. Messages are operations that the object canperform.

Registration Manager

Course Allotment

(confirmation)

A.B.Chowbe




Object Characteristics - Identity

Every object has an unique identity. Two objects may havesame state, but can not have same identity.

Even if states of two objects are same, their identitiesshould be different. (Employee No. may work as identity)

A.B.Chowbe

teaches OOPA.B.Chowbe

teaches OOP




Class

A Class is a description of a group of objects with commonproperties (attributes) & behavior (operations)

An object is an instance of a class

eg. A.B.Chowbe is an object of Teacher class

Example: Course Class

Properties Behavior

Name Add a student

Location Delete a student

Days offered Get course roster

Credit hours Determine if it is fullStart time

End time




Class & Object

A class is an abstract definition of an object

It defines the structure and behavior of each object in the class

It serves as a template for creating objects

Contains attributes & operations

Objects are grouped into classes

P.A.Walter G.A.Khanna A.B.Chowbe

Teacher




Class Elements

Attributes

CourseOffering

number startTime

endTime

..

:CourseOffering

Number=CS201

endTime=1230startTime=1030

..

:CourseOffering

Number=CS202


Class

Object

Object




Class Elements (Contd«)

Operations

CourseOffering

number

Add StudentDelete StudentGet Start TimeGet End Time

startTimeendTime

..

:CourseOffering

Number=CS201


..

:CourseOffering

Number=CS202


Class

Object

Object



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Abstraction

Abstraction is the process of hiding the details and exposingonly the essential features of a particular concept or object

In abstraction, one captures only the essential attributes andbehaviors of a component

Example:

Telephone has a lot of attributes such as colour, shape,model make and behaviors such as receive call, make call.Internally, it is made up of circuits, chips and othercomponents. But to buy or use a Telephone, we don't needto know the internal workings of the phone.




Encapsulation

Encapsulation: Implementation details are hidden from theoutside world

Encapsulation is the way by which abstraction is achieved

Example:

The electronic circuit used in the telephone is hidden from theuser. This is Encapsulation.




What is an Interface?

An interface provides a collection of operations that are usedto specify a service of a class or a component

An interface is the fundamental means of communicationbetween objects

Each class design specifies the interfaces for the properinstantiation and operation of objects

Any behavior that the object provides must be invoked by a

message sent using one of the provided interfaces

Polygon

Draw

Move

Scale

Rotate

Interface




Message Passing among Objects

Data

Function

Data

Function

Data

Function

Data

Function

State (Data) is kept

accessible only to a

set of functions.

Behavior of theobject is exposed

using methods.

An object communicates

with another object by

passing messages

(invoking methods)




Relationship among Classes

Composition (Has-A Relationship)Defines a composite object type

Example:Object of Color is an attribute of Automobile class Automobile

Color shade

Color string name

int red;

int green

int blue

Has-A Relationship




Relationship among Classes

Inheritance (Is-A Relationship)

Hierarchy according to level of abstraction

When the classes have µis a kind of¶ relationship between them,this relationship is inheritance

Increasing

Generalization

Increasing

Specialization

Art

Music Films

Classical Rap

Commercial Documentary

Parent- Child

relationship(Is-A Relationship)




Types of Inheritance

Single inheritance

Classes have single parent class

Bank Account

balance

number

name

Withdraw()

CreateStatement()

Current Account

Withdraw()

Saving Account

GetInterest()

Withdraw()

Subclasses

Superclass

(parent)

Ancestor

Descendents

GeneralizationRelationship




Types of inheritance

Multiple inheritance

One class has more than one parent class

Flying Entity Animal

Airplane Helicopter Bird Wolf Horse

multiple

inheritance

Subclass/ChildClass/Derived

Class

SuperClass/Parent

Class/Base Class




What is inherited?

A subclass inherits its parent¶s attributes, operations

A subclass may:

Add additional attributes, operations

Redefine inherited operations (i.e. overriding)

Common attributes & operations are shown at the highestapplicable level in the hierarchy




Polymorphism

The ability of one thing to appear in many forms dependingon context

Volume Control

Channel Control

Surrounding control

Sound Equaliser control

Common Interface

Videocon TV Samsung TV SansuiVideo

Remote

Volume Control

Volume

Control

Volume Control

Same functionality is implemented in

different devices in different manner.




Polymorphism

The ability of the objects to respond to the same message indifferent ways is also called as polymorphism

1. Give me a ring

3. Give me a ring

2. Dial a phone no.

4. Gives an engagement ring




Overloading & Overriding

Two ways of achieving Polymorphism

Overloading

The ability of the objects to respond to the same message indifferent ways is achieved using overloading

Overriding

The ability to respond differently than the parent, is achived usingoverriding




Summary

In this session, we have covered:

Object

Class

Abstraction

Encapsulation

Message Passing

Inheritance

Polymorphism



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ITP OO Concepts