introduction to oop lec one

8/9/2019 Introduction to OOP Lec One

1/23

Advance Programming Using Java

Designed by : Atif Azeem Khan

Introduction to JavaIntroduction to JavaLecture One


2/23

Applied Programming Using Java

ObjectivesObjectives

What is OOPsWhat is OOPs

Classes and ObjectsClasses and Objects

Difference between Object & ClassDifference between Object & Class

Class and Object Methods and DataClass and Object Methods and Data What is Data Abstraction & Encapsulation?What is Data Abstraction & Encapsulation?

What is Polymorphism?What is Polymorphism?

Graphical representation of Class & ObjectGraphical representation of Class & Object

Constant & variable data membersConstant & variable data members


3/23

What is OOPsWhat is OOPs

OOP stands for Object Oriented ProgrammingOOP stands for Object Oriented Programmingis a programming paradigm that usesis a programming paradigm that usesabstraction to create models based on the realabstraction to create models based on the realworld. It provides for better modelling of theworld. It provides for better modelling of thereal world object into computer systemreal world object into computer system

The power of objectThe power of object--oriented systems lies inoriented systems lies in

their promise of code reuse which will increasetheir promise of code reuse which will increaseproductivity, reduce costs and improveproductivity, reduce costs and improvesoftware qualitysoftware quality



4/23

Why OOPs ?Why OOPs ?

A major factor in the invention of OOPs approach isA major factor in the invention of OOPs approach isto remove some of the flaws encountered with theto remove some of the flaws encountered with theProcedural/Structured approach.Procedural/Structured approach. In OOP, data isIn OOP, data istreated as a critical element and does not allow it totreated as a critical element and does not allow it to

flow freely. It bounds data closely to theflow freely. It bounds data closely to the functionsfunctionsthat operate on it and protects it from accidentalthat operate on it and protects it from accidentalmodification from outside functions.modification from outside functions. OOP allowsOOP allowsdecomposition ofdecomposition of a problem into a number ofa problem into a number ofentities called objects and then builds data andentities called objects and then builds data and

functions around these objects.functions around these objects.A major advantageA major advantageof OOP is code reusability.of OOP is code reusability.



5/23

Advantages of OOPsAdvantages of OOPs

Some important features of Object OrientedSome important features of Object Orientedprogrammingprogramming are as follows:are as follows:

Emphasis on data rather than procedure.Emphasis on data rather than procedure. OOP has been hailed for its naturalness; understand ability,OOP has been hailed for its naturalness; understand ability,

extensibility, reusability, and easeextensibility, reusability, and ease--ofof--maintenance.maintenance. Programs are divided into Objects.Programs are divided into Objects. Data is hidden and cannot be accessed by external functions.Data is hidden and cannot be accessed by external functions.

Objects canObjects can communicatecommunicate with each other through functions.with each other through functions. New data and functions can be easily added wheneverNew data and functions can be easily added whenever

necessary.necessary. Follows bottomFollows bottom--up approach.up approach.



6/23

Advantages of OOPsAdvantages of OOPs

ObjectObject--Oriented Programming has the followingOriented Programming has the followingadvantages over conventional approaches:advantages over conventional approaches: OOP provides a clear modular structure for programsOOP provides a clear modular structure for programs

which makes it good for defining abstract data typeswhich makes it good for defining abstract data types

where implementation details are hidden and the unitwhere implementation details are hidden and the unithas a clearly defined interface.has a clearly defined interface.

OOP makes it easy to maintain and modify existing codeOOP makes it easy to maintain and modify existing codeas new objects can be created with small differences toas new objects can be created with small differences toexisting ones.existing ones.

OOP provides a good framework for code librariesOOP provides a good framework for code librarieswhere suppliedwhere supplied softwaresoftware components can be easilycomponents can be easilyadapted and modified by theadapted and modified by the programmerprogrammer . This is. This isparticularly useful for developing graphical userparticularly useful for developing graphical userinterfaces.interfaces.



7/23

Structure Vs OOPsStructure Vs OOPs

Program divided into smallProgram divided into smallsub programs calledsub programs calledfunctions. Data andfunctions. Data and

functions are separatefunctions are separatefunctions are the primaryfunctions are the primaryfocus. Different parts offocus. Different parts ofprogram has open access toprogram has open access todata. This follows the topdata. This follows the top

toto--bottom approach. Itbottom approach. Itinvolves writing programinvolves writing programtask specific.task specific.


Program divided into differentProgram divided into differentclasses. Data and Functionsclasses. Data and Functionsare integrated into classes.are integrated into classes.OOPs focus is on Data. AccessOOPs focus is on Data. Access

is limited to data members.is limited to data members.OOPs follows the bottomOOPs follows the bottom--upupdesign It involves writing adesign It involves writing amodular program from specificmodular program from specificto general. Easy to modify andto general. Easy to modify and

reuse the code written once.reuse the code written once.


8/23

Concept of OOPsConcept of OOPs

ObjectsObjects

ClassesClasses

Data Abstraction and EncapsulationData Abstraction and EncapsulationInheritanceInheritance

PolymorphismPolymorphism



9/23

Data Abstraction & EncapsulationData Abstraction & Encapsulation

AbstractionAbstraction refers to the act of representingrefers to the act of representingessential features without including theessential features without including thebackground details orbackground details or explanations. Classesexplanations. Classes

use the concept of abstraction and are defineduse the concept of abstraction and are definedas a list of abstract attributes.as a list of abstract attributes.

Storing data and functions in a single unitStoring data and functions in a single unit(class) is(class) is encapsulation.encapsulation. Data cannot beData cannot be

accessible to the outside worldaccessible to the outside world and only thoseand only thosefunctions which are stored in the class canfunctions which are stored in the class canaccessaccess



10/23

InharitanceInharitance

InheritanceInheritance is the process by which objectsis the process by which objectscan acquire the properties of objects ofcan acquire the properties of objects of

other class. In OOP,other class. In OOP, inheritanceinheritance providesprovidesreusability, like, adding additional featuresreusability, like, adding additional featuresto an existing class without modifying it.to an existing class without modifying it.This is achieved by deriving a new classThis is achieved by deriving a new class

from the existing one. The new class willfrom the existing one. The new class willhave combined features of both the classes.have combined features of both the classes.



11/23

Object & ClassesObject & Classes

Two most important concepts in objectTwo most important concepts in object--oriented programming are the classes &oriented programming are the classes &objects. In broadest term, an object is aobjects. In broadest term, an object is athing, both tangible and intangible, that wething, both tangible and intangible, that wecan imagine and class is a sketch or designcan imagine and class is a sketch or designor a definition how the object will beor a definition how the object will be

created.created.



12/23

PolymorphismPolymorphism

PolymorphismPolymorphism means the ability to takemeans the ability to takemore than one form. An operation maymore than one form. An operation mayexhibit different behaviours inexhibit different behaviours indifferentdifferent instances. The behaviour dependsinstances. The behaviour dependson the data types used in the operation.on the data types used in the operation.Polymorphism is extensively used inPolymorphism is extensively used in

implementingimplementing Inheritance.Inheritance.



13/23

ClassClass

As explain earlier class isAs explain earlier class isand actual blueand actual blue--print of anprint of anobject that defines theobject that defines the

rules or standards that willrules or standards that willbe followed to createbe followed to createthose object. Wethose object. Werepresent the class inrepresent the class ingraphical representationgraphical representation

with a rectangle with classwith a rectangle with classname on topname on top



14/23

ObjectObject

Object could be any thingObject could be any thingthat we can imagine or seethat we can imagine or seeeither it is tangible oreither it is tangible orintangible. An object alwaysintangible. An object alwayshave somehave some propertiesproperties andandexhibit someexhibit some behaviourbehaviour

for example,for example,Tree, plane, cat, paper,Tree, plane, cat, paper,keyboard, car house, lightkeyboard, car house, lightbulb, table, chair all arebulb, table, chair all areobjects.objects.



15/23

Object ExampleObject Example

Every single object is comprised of someEvery single object is comprised of somedatadata (properties)(properties) and operationsand operations(behaviour)(behaviour)

For example,For example,A car has some propertiesA car has some properties (data)(data) like model,like model,colour, doors, type, registrationcolour, doors, type, registration--no, engine sizeno, engine sizeand extra . And car also do some functionsand extra . And car also do some functions(behaviour)(behaviour) like it start, run fast, run slow,like it start, run fast, run slow,breakdown, and extra.breakdown, and extra.



16/23

Object Graphical representationObject Graphical representation

We represent object with round edgedWe represent object with round edgedrectangle with name on toprectangle with name on top


Object Car

moveFoward()

moveBackward()


17/23

Messages & Methods (Behaviour)Messages & Methods (Behaviour)

In objectIn object--oriented program we first defineoriented program we first defineclasses, and while the program is running weclasses, and while the program is running wecreate objects for these classes to accomplishcreate objects for these classes to accomplishtasks.tasks.

A task can range from adding two numbers toA task can range from adding two numbers tocomputing interest payment for a lone orcomputing interest payment for a lone orcalculating angle of a space shuttle.calculating angle of a space shuttle.

To instruct a class or an object we sendTo instruct a class or an object we sendmessages to it for example we send a messagemessages to it for example we send a messageof new car toof new car to class of carclass of car for an instance offor an instance ofobject carobject car..



18/23

For a class or an object to process that messageFor a class or an object to process that messageit must be programmed accordingly.it must be programmed accordingly.

For a class or an object to process message itFor a class or an object to process message itreceive, it must process a matching methodreceive, it must process a matching method(which is a sequence of instructions a class /(which is a sequence of instructions a class /object follows to perform a task).object follows to perform a task).

We define methods for classes & objects,We define methods for classes & objects,methods for classes calledmethods for classes called class methodsclass methodsandandmethods for object calledmethods for object called instance methodsinstance methods


Messages & Methods (Behaviour)Messages & Methods (Behaviour)


19/23

Object Method ExampleObject Method Example

Lets say we have and object Account andLets say we have and object Account andwe have defined a method called deposit.we have defined a method called deposit.


Account

deposit

250deposit

Deposit250


20/23

We send message toWe send message todeposit250 todeposit250 tomethod deposit andmethod deposit andmethod only depositmethod only depositit and does notit and does notreturn any thing toreturn any thing tosender. But somesender. But sometime we need totime we need to

information forminformation formclass or object inclass or object inthis casethis case


Account

getMonthlyFee

Monthly fee

Object Method ExampleObject Method Example


21/23

Class Methods ExampleClass Methods Example

Lets say we have a method that will give usLets say we have a method that will give usthe average balance of all the objects thatthe average balance of all the objects thathave been instantiated for class accounthave been instantiated for class accountthen.then.


Account

getAverageBalance

Average balance

You can not sendinstance message to

class


22/23

Class and Object Data Values orClass and Object Data Values or

PropertiesPropertiesLets remind the method deposit in AccountLets remind the method deposit in Account

instance(object) which receive ainstance(object) which receive amessage(value) form sender and aftermessage(value) form sender and afterreceiving where does it can store thatreceiving where does it can store thatvalue?value?

There comes the need for data member orThere comes the need for data member or

properties or data values.properties or data values.



23/23

We canWe candefinedefinefollowingfollowing

datadatamembers formembers fora accounta account

class andclass andinstance.instance.


Class and Object Data Values orClass and Object Data Values or

PropertiesProperties100

6427

Account

100 100100

This is a lock icon toindicate that a constant

value cannot change

Minimum balance

Account prefix

Opening BalanceOpening Balance Opening Balance

185.91558.91204.04

Current balance Current balance Current balance

Atifs AccToms AccAlis Acc

introduction to oop lec one

Documents