Oop lecture 2

CONNECTING THE DOTS

Learning OutcomesAt the end of this topic, the student is able to :-i. Model objects and classes using UML notationii. Model relationships of objects and classes using UML notationiii. Produce UML class diagram

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BITP 3113 Object Oriented ProgrammingSem I 2012/2013 Auhtored by Emma McKay-Fikri

II. UML OBJECT ORIENTED MODEL

BLAST FROM THE PASTRecap

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Principles of Object Oriented

• Identify classes, object and relationships

Abstraction

• Hiding information

Encapsulation

• Extending class definition

Inheritance

• Using the same name with different behavior

Polymorphism

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3BITP 3113 Object Oriented ProgrammingSem I 2012/2013 Auhtored by Emma McKay-Fikri

Object

• Objects are things that make sense to the application.

• Classes are collections of objects with the similar states and behavior.

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How to Identify Object?

• Object has Identity– What makes an object different from another object?

• Object has State– What is the data of the object?

• Object has Behavior– What the object can do?– What can we do with the object?

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Can You Identify Objects?>

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Defining a Class

• In object oriented programming,– Objects are created– Classes are defined

• Object is an instance of a class

• A class is a general definition for a group of objects that has similar characteristics and behavior.

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Designing a Class

• A class must have a Name– What is the unique name for a group of object?

• A class should have Instance variables– What the class should know?– What is the data or attribute of the class?

• A class should have Method– How to class act and react?– What is the name of the action and reaction?

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Can You Identify Classes?>

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DIAGRAMMING CLASSLesson 1

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Class Diagram

• Objects must interact in order to make the application function (and make sense thus reflects the real world model)

• Therefore, we need to model the relationship of the classes.

• In UML, a CLASS DIAGRAM is use to model the classes the relationships.

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Why Class Diagram?

• Class diagram represents the basics of Object Oriented System.

• It identifies what classes they are, how they interrelate and interact.

• It captures structure of object oriented system– Support architectural system

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What is UML?

• UML stands for Unified Modeling Language

• Its is a well-known and widely accepted modeling language for object oriented

• Further details, Google for UML.

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What is in a Class Diagram?>

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Player

PropertyOwner

Token

Property

House

picks+selectedToken +player

1 1

buy

+ownProperty

+player

0..*

1

TitleDeed

has

+property

+titleDeed

1

1

Street Utility RailwayStationBuilding

Hotel

develop

+buildings 1..*builds on

1..*

Class

Multiplicity

Association

Role

Composition

Generalization

Aggregation

Steps to Produce Class Diagram

Identify objects and classes.

•Define instance variables and methods.

•Define access rights (public/private)

Connect the classes.

•Name the connection.

•Define degree of connection.

Refine the classes and

relationships. (Iterative process)

•Enrich classes•Enrich the relationship

A class diagram

is produced

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MODELLING CLASSLesson 2

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Defining Class>

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Player

-name : String-totalSupplyMoney : float

+setName(name:String):void+getName( ):String+setTotalSupplyMoney(totalSupplyMoney:float):void+getTotalSupplyMoney( ):float+updateTotalSupplyMoney(amount:float):void

Many objects(Player in black t- shirt, Player in blue t-shirt)

One class

UML Notation for Access Rights

Public +

Protected #

Package ~

Private -

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Class Representation in UML>

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Class name

Instance variables

Methods

Compartment for instance variables and methods can be hide

Player

-name : String-totalSupplyMoney : float

+setName(name:String):void+getName( ):String+setTotalSupplyMoney(totalSupplyMoney:float):void+getTotalSupplyMoney( ):float+updateTotalSupplyMoney(amount:float):void

Designing Instance Variables

• A class should have Instance variables– What the class should know?– What is the data or attribute of the class?

• An instance variable tells what is the data and the type of the data a class should have or know.– At times, an instance variables tell how much it should exist

at one particular time.

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Modeling Instance Variables

• An instance variables should have the following:-– Name : What the data to be known as?– Type : What is the type of the data?– Visibility : Is it accessible to external of the class?– Multiplicity : How many of the data should exist?– Default value : What is the default value of the data?

• Format

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visibility name : type [multiplicity] = default-value

Modeling Instance Variables

• In this case, the instance variables do not have multiplicity• This is considered as single instance variables

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visibility(private)

- totalSupplyMoney : float = 0

name

type default-value

Designing Methods

• A class should have Method– How to class act and react?– What is the name of the action and reaction?

• A method will tell what it should do, what is the additional information to be supply and what it will return.

• A method is similar as function in structured programming.

• A good method will do only one task/job.

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Modeling Method

• A method should have the following– Name

• What the method wants to be known as?

– List of parameters • Additional data to be supply in order to make the method works

– Return type• Type of information to be returned to the caller of the method

– Visibility• Accessibility to external class

• Format

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visibility name (parameter-list) : return-type

Modeling Method>

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+ updateSupplyMoney (amount:float) : void

visibilty name (parameter-list) return-type

CONNECTING OBJECTSLesson 3

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Relationships

• One object is related to another in order to make it work in the environment.

• Example, Player picks Token• Two objects are interacting

– Player object– Token object

• Thus, we can say Player and Token has a relationship

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Association

• Association is general relations define for two objects

• If two objects are interacting, we can say the objects are associating.

• For example , the Player object associating with the Token object.

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Representing Association

• Association is represented using a solid line• It connects/relates two objects

• The association must be named

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Player Tokenpicks

association

Association & OO Programming

• What does an association means in the context of programming?

• Objects are interacting.• Those interactions means the objects are

communicating.• Objects communicate through message passing.

• From programming point of view, message passing is invoking/calling method in the other object.

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Knowing the Other Side

• Association tells how one class knows the other class in order to perform its work.

• This ‘knowing’ needs a direction. The direction is known as Navigability in UML.

• Two types of navigability– Unidirectional association– Bidirectional association

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Unidirectional Association

• Unidirectional is represented using solid arrow in UML.

• This means, one end is aware of the existence of the other ends.

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Interpreted as :-

•Player has the responsibility to tell which token he pick but token no corresponding ability to tell which player it has.•Player is aware of token existence.

Player picks Token

Bidirectional Association

• Bidirectional is represent using solid arrow at both end.

• Both ends are aware of each other existence.

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Player Tokenowning

Interpreted as :-

•Player has the responsibility to tell which token he owns and token has the ability to tell which player is owning it.•Player and Token is aware of each other existence.

NEW MEMBERLesson 4

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Real World is Complex

• In real world object is complex.• An object may consist of many other objects.

• For example:-

• How would you define type for dateOfBirth?– Integer?– String?– Other types?

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Player

-name : String-dateOfBirth:?

Designing New Type

• Normally we used primitive type to define type for instance variables – int, float, double, char.

• Often, we used String for name, for example.– Well, String is never a primitive type.

• dateOfBirth consists of day, month, year.– day : int– month : could be int or String (depends on the format)– year : int

• Therefore, we need to define new class to represent dateOfBirth.

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Designing New Class

• Let’s design new class to represent dateOfBirth. • Let’s make it general and called it Date

– So that it would be a general class

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Date

-day:int-month:String-year:int

+createDate(day:int, month:String, year:int): String

Directed Association as New Member

• Player is associated with Date.• Thus, we can create a new object of Date (that is

dateOfBirth) as new member of Player.

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Date

-day:int-month:String-year:int

+createDate(day:int, month:String, year:int): String

Player

-name : String-dateOfBirth:Date

birth on

Degree of Participation

• Each instance variable will exist as one copy of member to the class.

• For example :-

• Each player will have only ONE dateOfBirth– Not other player will have more than one dateOfBirth,

right?

• This degree is known as multiplicity

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Player

-name : String-dateOfBirth:Date

Multiplicity

• Multiplicity indicates how many object participate in the relationship

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Player Tokenpicks

11

Interpreted as :-One player object can picks only one token

object.

Player Propertybuy

0..*1

Interpreted as :-One player object buys no property or more

property.

Range of Multiplicity

• Single– Any single number– * indicate infinity

• Range– Example : 2...4, 0 ... *, 1 .. *

• A discrete set– Example : 2,4

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SUPER MODEL(ING)Lesson 5

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Super Class & Sub Class

• The relationship between super class and sub class is modeled using generalization.

• Thus, model inheritance.

• In UML, generalization is using a solid line with hollow arrow head.

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Modeling Inheritance>

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Player

PropertyOwnerSub class

Super class

is-a relationship

Interpreted as :-• PropertyOwner is a kind of Player.• PropertyOwner can develop property.• PropertyOwner inherits all public (package and protected) attributes

and methods from Player.• Every PropertyOwner is a Player.

Generalization>

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Player

-name: String-selectedToken: Token-totalSupplyMoney: Float = 0

+setName(playerName: String): void+getName(): String+setSelectedToken(Token: token): void+getToken(): Token+setSupplyMoney(money: Float): void+getSupplyMoney(): Float+updateSupplyMoney(amount: Float): void

PropertyOwner

-house: House[1..*]-hotel: Integer[0..1]-utilities: Utility[0..*]-railroad: Railroad[0..*]

+developHouse(noOfHouses: Integer): void+developHotel(): void+mortgageHouse(street: Street): Float+mortgageHotel(street: Street): Float+mortgageUtilities(): Float+mortgageRailroad(): Float

Interpreted as :-

• Player can buy property.• When Player buy property, he

is a PropertyOwner.• Only PropertyOwner can

develop House or Hotel on the street.

• Only PropertyOwner can mortgage house, hotel, utilities and/railroad.

• PropertyOwner is-a Player.

RICHER RELATIONSHIPLesson 6

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Variants of Relationships

• Relationships is not limited to directional association and generalization.

• Each type of relationship bring different meaning to the model.

• Some of the object may function if we remove it from the other object. Some may not.– Can you remove your legs and the legs still function by

it self?

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Advanced Relationship

• Therefor, a richer relationship is needed to describe the model precisely.

• This topic covers– Aggregation– Composition – Dependency

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Part and Whole

• Some object is made up from many objects.• In this case there are part-of object and whole-

object.• For example, a Car is made of Window, Door,

Tire, Engine etc.

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Whole Object Part-of Object

Modeling Aggregation

• Aggregation is the simplest part-of and whole object relationship.

• It is represented using solid line with hollow diamond head.

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Modeling Aggregation

• The Owner owns Station. • Therefore, Station is part-of Owner

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Owner

-name: String-capital: float-stationOwned: Station[1..*]

+setName(String name): void+getName(): String+setCapital(float capital): boolean+getCapital(): float

Station

-location: String

+setLocation(String location): void+getLocation(): String

owns

-stationOwned

1..*

Part-objectWhole-object Aggregation

Modeling Composition

• Composition is a stronger version of aggregation.

• It is represented by solid line and filled diamond-end

• The part may belong to only one whole object.• The part-object may live and die with the whole

object.

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Modeling Composition>

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Property

-Name: String-Price: Float-Group: String

+DisplayProperty()

TitleDeed

-RentalRate: Float[1..*]-MortgageRate: Float[1..*]

+getRentalRate(noOfProperty: Integer): Float+getMortgageRate(noOfProperty: Integer): Float

has

+property

+titleDeed

1

1

Interpreted as :-

Player buy a Property and the TitleDeed is given to the player.When PropertyOwner mortgage the Property to the bank, the TitleDeed is given to the Bank.

The existance of TitleDeed is fully depends on Property. If the owner of the Property changed, so will the TitleDeed.

Modeling Dependency

• At time, we need to use other object but not as member of the class.

• An object can be passed as a parameter of a methods.

• This can be modeled using Dependency in UML

• Dependency is modeled using dotted arrow in UML.

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Modeling Dependency>

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Interpreted as :-The Player is visible to push() method. Thus,

this is some kind of dependency.

Queue

-player: Player[0..*]

+push(player: Player): void+pop(): Player

Player

What Have You Learn Today?

Learning Outcomes Check Yourself Checked

i. Model objects and classes using UML notation

i. Create other classes in Monopoly Game using UML notation. (Complete with instance variables and methods)

ii. Model relationships of objects and classes using UML notation

i. Connects all classes using relationship.

ii. Give name and degree for the relationship.

iii. Produce UML class diagram

i. Refine classes, relationships and produce class diagram.

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THAT’S WRAP FOR TODAYSee You in the Next Class

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Oop lecture 2

Documents

Transcript of Oop lecture 2