Object Oriented Design And Programing

Object Oriented Design (OOD)in software industry

Available at www.elfuchs.com

Emmanuel FUCHS

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Why OOD ?

Design for changesProcedural Oriented Design (POD) VS Object Oriented Design (OOD)Procedural Oriented DesignObject Oriented DesignDesign Pattern

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OOD in software industryDesign for changes

Sources of ChangeDesigning and programming in future tense

Procedural Oriented Design (POD) VS Object Oriented Design (OOD)Procedural Oriented Design

Design The Problem StatementConsequence of Problem Statement changeState and Procedure Dichotomy

Object Oriented DesignIntegrate State and ProcedureDesign A Solution StatementNo Consequence of Problem Statement change

GOF Design PatternFactoryState pattern

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Changes Request : flexible solution

Productive programmerInitial Request

1 Day After

Unproductive programmer

1 Week After

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Productive programmerEvolution

RequestInitial Request

1 Day After


1 Week After

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1 Day After

1 Week After


1 Day After

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1 Day After

1 Week After

Few Weeks Later


1 Day After

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Productive programmer


Evolution Request

Initial Request

1 Day After

1 Week After

Few Weeks Later

1 Day After

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Unproductive programmerEvolution


1 Day After

1 Week After

Few Weeks Later

Productive programmer

1 Day After

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Changes Sources During Development

Requirements :Customers Discover What they Really Want During or at the End of Developments

TechnologyPerformances Are Increasing With Time

SkillWe Learn and Understand the Problem and We Discover the Right Solution on the Job

Short Term PoliticNo Comments

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program in the future tense.

Initial Request

1 Day After

Present tenseprogramming Short term

Medium to long term1 Week After

Future tenseprogramming

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program in the future tense.

Initial Request Evolution Request

1 Week After

Few Weeks Later

1 Day After

Present tenseprogramming

1 Day After

Future tenseprogramming

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Object VS Procedural

ProceduralThe code solution “structure” is the problem “structure”.When problems “changes” the code structure changes.

ObjectThe solution is based on integration and collaboration of independent entities (component).An entity is a code subset.Integration and Collaboration are managed by tools (compiler).When the problems “changes” the collaboration scheme changes not entity’s code.

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User Input

Operation:

A: Addition

B: Subtraction

C: Division

E: Multiplication

Enter a choice =>

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User Input

Operation: Addition

A: First Integer

B: Second Integer

Enter a choice =>

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Procedural Programming

Proc A1()

Proc a ()

CH = 1

Proc b ()

CH = 2

Proc c ()

CH = 3

CharacterInput CH

Proc A2() Proc A3()

Procedure A ()

CH = A

Proc d ()

CH = 1

Proc e ()

CH = 2

Proc f ()

CH = 3

CharacterInput CH

Procedure B ()

CH = B

Proc g ()

CH = 1

Proc h ()

CH = 2

CharacterInput CH

Procedure C()

CH = C

CharacterImput CH

case

case

case

case

case

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Hierarchical Programming

Tapez un nom iciTapez un titre de fonction ici




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User Input : Operation in R and C

Operation:

A: Real

B: Complex

Enter a choice =>

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User Input

Operation: Complex Addition

A: First Number real part

B: First Number imaginary part

C: Second Number real part

D: Second Number imaginary part

Enter a choice =>

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Initial Request

1 Day After

1 Week After

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1 Day After

1 Week After

Few Weeks Later

1 Day After

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Hierarchical, Structural Programming, “Top Down”

Reuse of Real operations for Complex Operations

Procedures

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Procedures

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Procedures

Spaghetti Plate

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State and Procedure dichotomy

State Procedures

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State Procedures

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State Procedures

Spaghetti Plate

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Object Paradigm

GOF definition for object: A run-time entity that packages both data and the procedures that operate on that data.

ObjectObject

OperationOperation

OperationOperation

OperationOperation

OperationOperation

Data

Attribute Interfaces

GoF stand for Gang of Four. It refers to the famous books of Vlisside and Co. Design Patterns: Elements of Reusable Object-Oriented Software.

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Object Paradigm

GOF definition for object: A run-time entity that packages both data and the procedures that operate on that data.

UML class

ObjectObjectName

Attribute

OperationOperationOperationOperation

OperationOperation

OperationOperation

OperationOperation

OperationOperation

Data

Attribute InterfacesUML: Unified Modelling Language


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Object analogy

A driver doesn't care of engine's internal working.He only knows the interface

Implementation Interface

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Object analogy



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Object analogy



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Polymorphism

Interface

(specification) Implementation

(body)

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Object Interface

UML class

Name

Attribute


Object Interface

Client

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Object Interface and Implementation

Name

Attribute


UML class

Object Interface

Client

Interface Implementation

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Object Interface and Implementation

Name

Attribute


UML class

Object Interface

Client

Interface Implementation

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Object collaboration

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OOD hides the problem space

With OOD likely to change aspects are encapsulated and hidden to other objects.

How and What are separated

The problem : What

The solution : How

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The problem is in the User Input

Colour

A: Black,B: Brown,C: Red, D: Orange,E: Yellow,F: Green, G: Blue,

Enter a colour =>

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Replace case and enum by object .

enum Color {

Black,Brown,Red, Orange,Yellow,Green,Blue,

}

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structural switch

static void printsColor(int Value) {

switch(Value) {

case Black : processing 1

case Brown:processing 2

case Red:processing 3

case Orange:processing 4

case Yellow:processing 5

case Green:processing 6

case Blue:processing 7

} }

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structural switch

static void flightUpdate(intstatus) {

switch(status) {

case NIL_EXIT_STATE: processing 1

case FLIGHT_ACTIVATION_PROPOSAL:processing 2

case FLIGHT_ACTIVATION_ALARM:processing 3

case FLIGHT_ACTIVATION_CONFIRMED:processing 4

case HANDOVER_TRANSFERED,processing 5

case COORDINATION_TERMINATED,processing 6

case UNKNOWN_EXIT_STATEprocessing 7

} }

static void flightUpdate(int status) {

switch(status) {

case NIL_EXIT_STATE : processing 1







} }


switch(status) {








} } Software

Module BSoftwareModule A Software

Module D


switch(status) {








} }


switch(status) {








} }

SoftwareModule C

SoftwareModule E

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The problem space and the solution space.

If the switch value reflects the problem for example user inputs.

When the user request new case you have to change everywhere you use the switch value.

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Example 3: The problem is in the User Input

Colour

A: Black,B: Brown,C: Red, D: Orange,E: Yellow,F: Green, G: Blue,H: NewColor,

Enter a colour =>

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Replace case and enum by object .

enum Color {

Black,Brown,Red, Orange,Yellow,Green,Blue,NewColor,

}

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structural switchstatic void printsColor(int Value) {

switch(Value) {

case Black : processing 1

case Brown:processing 2

case Red:processing 3

case Orange:processing 4

case Yellow:processing 5

case Green:processing 6

case Blue:processing 7

case NewColor,processing 7

} }

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structural switch


switch(status) {








} }


switch(status) {








} }


switch(status) {








} }


switch(status) {








} }


switch(status) {








} }

SoftwareModule A

SoftwareModule B

SoftwareModule C

SoftwareModule D

SoftwareModule E

Changes

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structural switch


switch(status) {








} }


switch(status) {








} }


switch(status) {








} }


switch(status) {








} }


switch(status) {








} }

SoftwareModule A

SoftwareModule B

SoftwareModule C

SoftwareModule D

SoftwareModule ESpaghetti Plate

Changes

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Initial Request

1 Day After

1 Week After

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1 Day After

1 Week After

Few Weeks Later ?

1 Day After

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The object solution

Polymorphism

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Polymorphism

Print()Color

+print()

Client

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Polymorphism

Color

+print()

No Changes

Print()Client

Black

+ print()

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Polymorphism

Color

+print()

Brown

+ print()

No Changes

Print()Client

Black

+ print()

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Polymorphism

Color

+print()

Brown

+ print()

Red

+ print()

No Changes

Print()Client

Black

+ print()

Blue

+ print()

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Polymorphism

Color

+print()

Brown

+ print()

Red

+ print()

No Changes

Print()Client

Black

+ print()

Blue

+ print()

newColor

+ print()

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Object Polymorphism

Code example

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Polymorphism

Print()Color

+print()

Client

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Polymorphism

Color

+print()

Print()Client

Black

+ print()

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Code of the Black object print() operation

class Black extends Color

{

public void print()

{

System.out.println( " Black "); }

}

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Polymorphism

Color

+print()

Brown

+ print()

Print()Client

Black

+ print()

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Code of the Brown object print() operation

class Brown extends Color

{

public void print()

{

System.out.println( " Brown "); }

}

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Polymorphism

Color

+print()

Brown

+ print()

Red

+ print()

Print()Client

Black

+ print()

Blue

+ print()

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Code of the Red object print() operation

class Red extends Color

{

public void print()

{

System.out.println( " Red "); }

}

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Code of the Blue object print() operation

class Blue extends Color

{

public void print()

{

System.out.println( " Blue "); }

}

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Polymorphism

Color

+print()

Brown

+ print()

Red

+ print()

Print()Client

Black

+ print()

Blue

+ print()

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Polymorphism

Color

+print()

Brown

+ print()

Red

+ print()

No Changes

Print()Client

Black

+ print()

Blue

+ print()

newColor

+ print()

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Code of the Blue object print() operation

class NewColor extends Color

{

public void print()

{

System.out.println( " NewColor "); }

}

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GOF

GoF stand for Gang of Four. It refers to the pattern seminal book of John Vlissides, Erich Gamma, Richard Helm, Ralph Johnson:

Title: Design Patterns: Elements of Reusable Object-Oriented Software.

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GOF: The book cover

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Design Pattern GOF Definition

A design pattern systematically names, motivates, and explains ageneral design that addresses a recurring design problem inobject-oriented systems. It describes the problem, the solution, when to apply the solution, and its consequences. It also gives implementation hints and examples. The solution is a general arrangement of objects and classes that solve the problem. The solution is customized and implemented to solve the problem in a particular context.

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Why Design Pattern ?

Because we want to use polymorphism to manage the changesBut it is very difficult to find the object class lattice which leads to polymorphismDesign pattern Language is a catalogue of object class lattices which handle a certain problem with polymorphism.

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What to Expect from Design Patterns

A Common Design VocabularyA Documentation and Learning AidAn Adjunct to Existing MethodsA Target for Refactoring

Anti pattern are also useful.

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Design Pattern Catalogue

Creational PatternsAbstract Factory Builder Factory Method Prototype Singleton

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Structural PatternsAdapter Bridge Composite Decorator Facade Flyweight Proxy

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Behavioral PatternsChain of Responsibility Command Interpreter Memento Iterator Mediator Observer State Strategy Template Method Visitor

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Design Pattern Map

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What to Expect from Design Patterns

A Common Design VocabularyA Documentation and Learning AidAn Adjunct to Existing MethodsA Target for Refactoring

Anti pattern are also useful.

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The GOF Abstract Factory Design Pattern

*GoF stand for Gang of Four. It refers to the famous books of John Vlissides, Erich Gamma, Richard Helm, Ralph Johnson. Design Patterns: Elements of Reusable Object-Oriented Software.

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Factory Pattern

Color

+print()

Print()

Brown

+ print()

Red

+ print()

UNKNOWN_EXIT_STATE

+ print()

ColorFactory

+ create()

Client

Black

+ print()

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Factory Pattern

The switch is now hidden in the object state factory.

The factory returns a new object of the right derived class by using a switch case on the state integer code.

The client always sees the root class object type Color.

Each state object know how to manage client invocation in its case.

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Factory pseudo code

static color create(int Color) {

switch(Color) {

case Black : return color = new black();break;

case Brown:return color = new brown();break;

case Red:return color = new red();break;

case Orange : return color = new Orange();break;

case Yellow: return color = new Yellow();break;

case Green : return color = new Green();break;

case Blue : return color = new Blue();

} }

New Object

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Dynamic Polymorphism

Static polymorphism (Factory)State machine

Pattern State creates one object for each state and uses polymorphism to enable transparent client invocation.

Dynamic Polymorphism

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State Pattern (from the GoF)


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State model transformation

ColorRequest()

Client

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State diagram

Brown

Request()

Black OrangeRequest()

Request()

Request()Red

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structural switch

static void printsState(int state) {

switch(state) {

case Black :

System.out.println( “Black"); break;

case Brown :

System.out.println( “Brown"); break;

case Red :

System.out.println( “Red"); break;

case Orange :

System.out.println( “Orange"); break;

} }

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structural switch

static void printsState(int state) {

switch(state) {

case Black :

System.out.println( “Black"); break;

case Brown :

System.out.println( “Brown"); break;

case Red :

System.out.println( “Red"); break;

case Orange :

System.out.println( “Orange"); break;

} }

Spaghetti Plate

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ColorRequest()

Client

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ContextRequest()

Client

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HelloContextRequest()

OrangeHandle()

ColorHandle()

BrownHandle()

Client

BlackHandle()

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HelloContextRequest()

OrangeHandle()

BlackHandle()

ColorHandle()

BrownHandle()

Context

Concrete state

Client

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Polymorphism and state patterns

If we have an object which state can change during its lifetime and we have to perform different operations according to the object state we use the pattern state.

pattern State avoids switch even if the state of the object is changing

pattern State creates one object for each state and uses polymorphism to enable transparent client invocation.

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Objective

State pattern avoid structural switchNo enumeration in Java

An enumeration may be managed as a state machine.

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Next step

Model Driven DevelopmentCode generation

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Second order polynomial

The problem1° requirements change2° requirements changeProcedural solutionInitial requirements1° requirements change2° requirements changeObject SolutionPolynomial FactoryInitial requirements1° requirements change2° requirements change

Object Oriented Design (OOD)in software industry

The second order polynomial example

Emmanuel FUCHS

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1



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Second order polynomial equation

02 =++ cbxax

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Second order polynomial equation roots:

aacbbx

242 −±−

=

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Second order polynomial discriminant :

acb 42 −=∆

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X1 X2

y

First iteration : find roots in R

x

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Initial Request

1 Day After

1 Week After

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1 Day After

1 Week After

Few Weeks Later

1 Day After

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Second iteration : find roots in C

X1 X2

j

x

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Initial Request

1 Day After

1 Week After

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1 Day After

1 Week After

Few Weeks Later

1 Day After

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Third iteration : Checks Roots Interval

y

X1 X2

X

x

XX

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Initial Request

1 Day After

1 Week After

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1 Day After

1 Week After

Few Weeks Later ?

1 Day After

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Procedural solutionStart

Input coefficients a,b,c

Computes discriminantDelta = b * b – 4 * a * c

Computes single root

= 0

< 0> 0 DiscriminantSign

Computes roots

print roots print root print no roots

End

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Source code

delta = (b*b) - (4*a*c); // discrimant computation

if (delta < 0.0) { System.out.println (" No roots");

}

else if (delta > 0.0) { System.out.println (" Two roots :"); System.out.println (" x1 = " + (-b + Math.sqrt(delta))/ (2.0 * a)); System.out.println (" x2 = " + (-b - Math.sqrt(delta))/ (2.0 * a));

}

else { System.out.println (“ Single root: "); System.out.println (" x = " + (-b / (2.0 * a)));

}

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Procedural solutionStart



Computes single root

= 0

< 0> 0 DiscriminantSign

Computes roots

print roots print root print no roots

End

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Procedural solution Complex roots

Start


DiscriminantSign

Computes double rootComputes roots

print roots print root print roots


End

< 0

= 0

> 0

Computes Complex roots

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Source code



}


}


}

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Source code first modification



}


System.out.println (" Complex roots"); System.out.println (" x1 real part = " + (-b / (2.0*a))); System.out.println (" x2 imaginary part = " + (-b - Math.sqrt(-delta))/ (2.0*a)+ "i"); System.out.println (" x2 real part = " + (-b / (2.0*a))); System.out.println (" x2 imaginary part= " + (-b - Math.sqrt(-delta))/ (2.0*a)+ "i");

}


}

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Functional evolution : Checks Roots Interval

y

X1 X2

X

x

XX

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Checks Roots Interval : procedural solution

End

< 0> 0

( /X1/ <= X & X <= /X2/ )

Return True Return False

F FT

DiscriminatSign

= 0Computes root case 1 Computes roots case 2 2

TX == X1

Return True Return False Return False

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Initial Request

1 Day After

1 Week After

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1 Day After

1 Week After

Few Weeks Later ?

1 Day After

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Source Code

static boolean isInBetweenRoots(double x,double a,double b, double c) {

double delta, x1, x2; delta = (b*b) - (4*a*c);

if (delta < 0.0)

return false;

else if (delta > 0.0) {

System.out.print("delta > 0"); x1 = (-b + Math.sqrt(delta))/ (2.0*a); x2 = (-b - Math.sqrt(delta))/ (2.0*a); return (Math.abs(x1) <= Math.abs(x)) && (Math.abs(x) <= Math.abs(x2));

}

else { x1 = -b / (2.0 * a); return (x == x1);

} }

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First Object Model : Domain Model

Second OrderPolynomial

Single RootSecond Order

Polynomial

Two RootsSecond Order

Polynomial

No RootSecond Order

Polynomial

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First Object Model : Domain Model

Second OrderPolynomial Discriminant


Polynomial


Polynomial

No RootSecond Order

Polynomial

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First Design Model with operation


computeRoots()

Double aDouble bDouble c

Discriminant


Polynomial

computeRoots()


Polynomial

computeRoots()

No RootSecond Order

Polynomial

computeRoots()

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Design Model Creation without Factory


computeRoots()create()


PolynomialcomputeRoots()



No RootSecond Order


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Domain Model


Discriminant

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Domain Model: Polynomial FactorySecond Order

Polynomial


Factory

Discriminant

create

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Domain Model: Polynomial FactorySecond Order

Polynomial


Factory

Discriminant

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First Design Model with operation


computeRoots()


Discriminant


Polynomial

computeRoots()


Polynomial

computeRoots()

No RootSecond Order

Polynomial

computeRoots()

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Discriminant

class Discriminant {

private double delta;

public Discriminant (double a, double b, double c) {

delta = (b * b) - (4.0 * a * c);

}

public double value () {

return delta; }

}

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Factory: Initial Requirements

static Polynome create( double a, double b, double c) {

Discriminant theDiscriminant = new Discriminant(a,b,c); double delta = theDiscriminant.value();Polynome polynome;

if (delta == 0.0) {

return polynome = new SingleRootPolynome(a,b,c,theDiscriminant) ; } else if (delta > 0.0) {

return polynome = new TwoRootsPolynome(a,b,c,theDiscriminant) ; } else {

return polynome = new NoRootPolynome(a,b,c,theDiscriminant); }

}

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Factory 1° Requirements Change

static Polynome create( double a, double b, double c) {

Discriminant theDiscriminant = new Discriminant(a,b,c); double delta = theDiscriminant.value(); Polynome polynome;

if (delta == 0.0) {

return polynome = new SingleRootPolynome(a,b,c,theDiscriminant) ; } else if (delta > 0.0) {

return polynome = new TwoRootsPolynome(a,b,c,theDiscriminant) ; } else {

return polynome = new ComplexRootsPolynome(a,b,c,theDiscriminant); }

}

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Design Model with operation


computeRoots()


Discriminant


Polynomial

computeRoots()


Polynomial

computeRoots()

No RootSecond Order

Polynomial

computeRoots()

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Computes root : Single Root Polynomial

void computesRoots() {

System.out.println (" Single root: ");

System.out.println (" x = " + (-b / (2.0*a)));

}

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computeRoots()


Discriminant


Polynomial

computeRoots()


Polynomial

computeRoots()

No RootSecond Order

Polynomial

computeRoots()

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Computes root : Two Roots Polynomial


System.out.println (" Two roots :");

System.out.println (" x1 = " + (-b + Math.sqrt(discriminant.value()))/ (2.0*a));

System.out.println (" x2 = " + (-b - Math.sqrt(discriminant.value()))/ (2.0*a));

}

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computeRoots()


Discriminant


Polynomial

computeRoots()


Polynomial

computeRoots()

No RootSecond Order

Polynomial

computeRoots()

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Computes root : No Root Polynomial


System.out.println (" No roots");

}

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1



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computeRoots()


Discriminant


Polynomial

computeRoots()


Polynomial

computeRoots()

No RootSecond Order

Polynomial

computeRoots()

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computeRoots()


Discriminant


Polynomial

computeRoots()


Polynomial

computeRoots()

Complex RootsSecond Order

Polynomial

computeRoots()

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Computes root : Complex Roots Polynomial


System.out.println (" Complex roots");

System.out.println (" x1 real part = " + (-b / (2.0*a)));

System.out.println (" x1 imaginary part = “

+ (-b + Math.sqrt(-discriminant.value()))/ (2.0*a)+ "i");

System.out.println (" x2 real part = " + (-b / (2.0*a)));

System.out.println (" x2 imaginary part = “

+ (-b - Math.sqrt(-discriminant.value()))/ (2.0*a)+ "i");

}

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1



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Design Model


computeRoots()isInBetweenRoots()



isInBetweenRoots()



isInBetweenRoots()

No RootSecond Order


isInBetweenRoots()

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Bracket the parameter : single root

boolean isInBetweenRoots(double x) {

return (x == x1);

}

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Design Model





isInBetweenRoots()



isInBetweenRoots()

No RootSecond Order


isInBetweenRoots()

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Bracket the parameter : Two roots


return (Math.abs(x1) <= Math.abs(x)) && (Math.abs(x) <= Math.abs(x2));

}

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Design Model





isInBetweenRoots()



isInBetweenRoots()

No RootSecond Order


isInBetweenRoots()

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Bracket the parameter : no roots


return false;

}

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That’s it !!!

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Thank You For Your Attention

Questions are welcomeContacts :

[email protected]

www.elfuchs.com

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