Object Oriented System Development Lecture 7 Classes ... · Rogardt Heldal Classes, Objects, and Relations - 3 - Mapping to code • One can map a UML class to many different code

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Rogardt Heldal Classes, Objects, and Relations - 1 -

Object Oriented System Development Lecture 7

Classes, Objects and Relations,

State Chart, OAL

Rogardt Heldal

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Obtaining operations

p2:Point

p1:Point

: Line move(p3)

2 Line

move(dist:Point):void

Point

x:double

y:double


1

Line

Point

X:double

Y:double

1 2

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Mapping to code • One can map a UML class to many different code skeletons in

different programming languages such as:

• In the previous lecture we showed a mapping to Java

• The focus of UML has mainly been on specifying software system gap between models and code can lead to inconsistency.

Point

x:double

y:double


Java

C#

C++

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BridgePoint • BridgePoint supports a subset of UML.

• BridgePoint strength is that the model can be executed.

• Model can be executed and tested!

• Model compilers take Models to code such as C, C++, C#, Java etc. BridgePoint comes with a compiler to C.

• No gap between models and code.

• Focus in this lecture is on UML 2, but we will also see BridgePoint relationship to UML 2.

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Executable Model Hierarchy

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Relationship between Model Elements

• Executable, tightly coupled: – Component

– Class

– State

– Action

• Informal, loosely coupled – Use Case

– Sequence*

– Communication*

– Activity

• Package

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UML Classes: Visibility

Point

- x:double

- y:double

+ move(dist:Point):void

Mapping visibility to java: • - -> private • # -> protected • + -> public • ~ -> package

(In this case the semantics of -,#,+,~ will be the one of Java.)

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UML attribute

UML: [visibility] name [multiplicity] [:type] [= initial value]

[{properties}]

Properties could be: – changeable (Variable may be changed.) – addOnly (When multiplicity is bigger than one you can add more

values, but not change or remove values.) – frozen (Cannot be changed after it has been initialized.)

• Example:

– x : int {frozen}

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Operations/methods

UML: [visibility] name [(parameter list)] [: return type] [{properties}]

You can have zero or more parameters. Syntax for parameters:

[direction] name : type [= default value] – direction: in, out, inout

• Example of a property – isQuery (no ”side effects”)

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Relations

• All the associations we consider when drawing domain models can also be used in class diagrams.

• But there are some interesting issues to consider …

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Navigability

Point Line 1 2

Line knows Point,

but Point doesn‟t know

Line.

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Association constraint

Constraint: • changeable (Links may be changed.) • addOnly (New links can be added by an object on the opposite

side of the association.) • frozen (When new links have been added from an object on

the opposite side of the association, they cannot be changed.) • ordered (Has a certain order) • bag (multisets instead of sets) • …

Company Person

{ordered}

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Class diagram elements in BridgePoint Class name

Attributes {

Association label

Verb phrase

Multiplicity, Conditionality

Tags: Class number Keyletters

BridgePoint do

not contain visibility

and properties

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Association names UML

Person Company * * employees employers

works for

Association name, Verb phrase

Role name,

Noun phrase

UML:

Person works for company

Can be read only one way

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Association names BridgePoint

Employee Company * * has currently works for

R1

Association label

Verb phrase

BridgePoint:

•Association label plays a key role in BridgePoint.

•It is used in the OAL Object Action Language (see later slides).

• To create link between objects (link is an instance of an association)

• To obtain objects over links

•BridgePoint generates automatically the association label.

Employee work for company

Company has currently employees

Can be read in both direction

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BridgePoint:tag

Bok {1,Bok}

Tags: Class number Keyletters

Class number is produced automatically by BridgePoint. As far as

I know we don‟t need to consider class numbers for the project.

A key letter will also be produced automatically, but this one you should

change to the same name as the class name!

• Keyletters is used in OAL

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Association Class

Company Person * *

Job

salary

Can be modeled in BridgePoint.

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Class methods and class variables

Account

-interestRate:double

-balance:double

+changeInterestRate(newinterestrate:double)

BridgePoint has support for class-based operations. Class-based

attributes has been on its way for some time, but is not supported yet.

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Class templates

Stack

+ empty():Boolean{isQuery}

+ push(e:T):Void

+ pop():T

- n: int

- s : T[size]

T

size:int

PersonStack

<<bind>>(Customer,10)

Stack<Person,10>

Not part of BridgePoint.

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Interface

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Interfaces

• Interfaces are very important. By using an interface you can separate implementation from specification.

• An interface specifies a service of a class

or component.

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Interfaces in UML

<<interface>>

AudioPlayer

play()

stop()

pause()

skipForward()

skipBackwards()

interface

DiscPlayer

In this lecture we will just look at interfaces connected to classes, but later we will also look at interfaces connected to components.

realization

MultiMedia

dependency

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The same interface

Here TapePlayer is a new implementation of AudioPlayer. If you have done everything correctly you only have to change the implementation of the methods in the interface, the rest of the program remains the same. The MultiMedia doesn‟t need to be changed!

TapePlayer

MultiMedia

<<interface>>

AudioPlayer

play()

stop()

pause()

skipForward()

skipBackwards()

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Dependency

DiscPlayer

MultiMedia

dependency

The class MultiMedia uses the methods in the interface, which are implemented by DiscPlayer.

DiscPlayer AudioPlayer

MultiMedia

dependency

realization <<interface>>

AudioPlayer

play()

stop()

pause()

skipForward()

skipBackwards()

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Interface Specifiers <<interface>>

IEmployer

getCompensation()

getBenefits()

Person Company - employer:IEmployer

1..* 1

A person can have many other roles, such as customer, boss, father, pilot etc.

Roles can be shown using interfaces.

Person - supervisor:IManager

- worker:IEmployee 1 *

- employees

works for

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Interface in BridgePoint • One does not model interfaces in the class diagram in

BridgePoint, but one models them when considering components (We will come back to components in a later lecture).

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Inheritance

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Example: Dwelling-house

DwellingHouse

#additionalInsulation:boolean

+ insulate()

super class

sub class

Inheritance

House

#length:double

#width:double

#numberOfFloors:int

#lastRenovation:int

+ area():double

# : visible with class and

in subclasses

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Instances

Sometimes you want to work with instances of House and sometimes with instances of DwellingHouse etc.

length = 20

width = 15

numberOfFloors = 2

:House

length = 30

width = 20

numberOfFloors = 3

additionalInsulation = true

:DwellingHouse

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leaf: stops inheritance public final class A { … } Note that also a method can be final. Then the method must not be

changed in the sub classes, e.g. public final int test (int x) { … }

A

{leaf}

B Not allowed!

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Multiple inheritance

• This is allowed in C++, but not in Java. (But: For interfaces in Java multiple inheritance is allowed)

• There are limitations on the use of the use of inheritance in BridgePoint. Staffan will come back to these points next week.

PrivateCar MotorBoat

AmphibiousCar

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xt-UML • xt-UML includes an action language OAL (Object Action

Language) to provide semantics to models.

• xt-UML is augmented with OAL.

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Case study • Now, we will show how to augment operations to obtain an

executable model

• You should learn this language by reading the OAL reference document found in the tool BridgePoint under the menu Help/Help Contents/BridgePoint UML Suite Help/ Reference/OAL Reference

• It is not a large document and you should be able to read it before the lecture on Thursday

• You will get more out of the lecture on Thursday if you read this document

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A small case study Library

xt-UML

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Book

ISBN

title

author

Exemplar *

exemplars

1

Lending

startDate

lendingPeriod

actualReturnDate

Borrower

name

SSNr

borrowId

* lendings

1

runningLending

0..1 0..1

AdmLib

addBorrower(name,SSNr)

isMember(SSNr)

addBook(ISBN,title,authore)

addExemplar(ISBN,

exemplarId,place)

searchExemplar(exemplarId)

borrowExemplar(SSNr,

exemplarId)

getBorrower(SSNr)

…

*

0..1

allBorrower

lentExemplar

allBooks

allE

xem

pla

r

exemplarId

place

id2

addExemplar(exemplarId,

place)

*

*

R1

R5

R6

R2 R4

R3

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addBorrower(name,SSNr) create object instance borrower of Borrower;

borrower.Borrower(name:param.name,SSNr:param.SSNr);

relate self to borrower across R1;

Borrower contains this method:

Borrower(name,SSNr) self.name = param.name;

self.SSNr = param.SSNr;

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isMember(SSNr)

select any borrower related by self -> Borrower [R1]

where selected.SSNr == param.SSNr;

return(not empty borrower);

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addBook(ISBN,title,author) create object instance book of Book;

book.Book(ISBN:param.ISBN,title:param.title,author:param.author);

relate self to book across R5;

Book contains this method:

Book(ISBN,title,author)self.ISBN = param.ISBN;

self.title = param.title;

self.author = param.author

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addExemplar(ISBN,exemplarId,place)

select any book related by self -> Book [R5]

where selected.ISBN == param.ISBN;

book.addExemplar(exemplarId:param.exemplarId,

place:param.place);

select any exemplar from instances of Exemplar

where (selected.exemplarId == param.exemplarId);

relate self to exemplar across R6;

To obtain an object, using links should be avoided as much

as possible. It is not very object oriented.

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SearchExemplar(exemplarId)

select any exemplar related by self -> Exemplar[R6]

where (selected.exemplarId == param.exemplarId);

select any bookHelper from instances of BookHelper;

if not empty exemplar

return exemplar.id2;

else

return bookHelper.NoBook;

end if; BookHelper

NoBook

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getBorrower(SSNr) select any borrower related by self -> Borrower [R1]

where selected.SSNr == param.SSNr;

if(not (empty borrower))

return borrower.borrowId;

end if;

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borrowExemplar(SSNr,exemplarId)

if (self.isMember(SSNr:param.SSNr))

borrower_ref = self.getBorrower(SSNr:param.SSNr);

select any borrower from instances of Borrower

where selected.borrowId == borrower_ref;

ex_ref = self.searchExemplar(exemplarId:param.exemplarId);

select any help from instances of BookHelper;

if not(ex_ref == help.NoBook)

select any exemplar from instances of Exemplar

where selected.id2 == ex_ref;

create object instance lending of Lending;

lending.Lending(startDate:TIM::current_date(),lendingPeriod:30);

relate lending to exemplar across R3;

relate borrower to lending across R2;

relate self to borrower across R1;

end if;

end if;

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Book(ISBN,title,author)

self.ISBN = param.ISBN;

self.title = param.title;

self.author = param.author;

addExemplar(exemplarId,place)

create object instance exemplar of Exemplar;

exemplar.Exemplar(exemplarId:param.exemplarId,

place:param.place);

relate self to exemplar across R4;

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Borrower(name,SSNr) self.name = param.name;

self.SSNr = param.SSNr;

Exemplar(exemplarId,place) self.exemplarId = param.exemplarId;

self.place = param.place;

Lending(startDate,lendingPeriod) self.startDate = param.startDate;

self.lendingPeriod = param.lendingPeriod;

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State Charts

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State Charts for Objects

• Describe the set of states an object can be in, and the transitions between states which can happen.

• State charts can be used when you e.g. want to model the whole life cycle of an object.

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Syntax

transition

• A transition is a directed relationship between a source vertex and

a target vertex. A vertex can be a state, final state, or a

pseudostate.

• <transition> ::= <trigger> [„,‟trigger][„[„guarded-constraint„]‟]

[„/‟action]

State name

initial state

final state

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Example: Library

Return an a copy of

a book.

Borrow a copy

of a book.

Borrower

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CRC

Book

Responsibility Collaboration

Maintain data for a book. Know if there is

a copy to borrow.

Copy


Maintain data for a certain copy of a book.

Inform corresponding book when the copy

is borrowed and returned.

Book

Library Member


Maintain data about borrowed book copies.

Handle requests to borrow and return book

copies.

Copy

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Collaboration

borrow(aCopy) 1:okToBorrow()

:Book

:LibraryMember

aCopy:Copy

2:borrow()

2.1 borrowed(aCopy)

return(aCopy)

:Book

:LibraryMember

aCopy:Copy

1:return()

1.1 returned(aCopy)

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Class Diagram

Book

returned(c:Copy)

borrowed(c:Copy)

book 1

*

Copy

return()

borrow()

-status:enum{OnShelf,Borrowed}

-status:enum{CanBeBorrowed,CanNotBeBorrowed}

copies

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Copy: State Chart

Borrowed

On the shelf

return()

borrow()

initial state state

event

Copy


Maintain data for a certain copy of a book.

Inform corresponding book when the copy

is borrowed and returned.

Book

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Actions

Book

Copy

State chart for Copy:

Borrowed On the shelf

return()/book.returned(self)

borrow()/book.borrowed(self)

initial state

returned(c:Copy)

borrowed(c:Copy)

book

1 *

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Conditions

Cannot be borrowed Can be borrowed

returned(copy)

borrowed(copy)

[copies->forall(

oclInState(Borrowed))]

returned(copy)

borrowed(copy)

[copies->exist(

oclInState(OnShelf))]

condition

State chart for Book:

Book


Maintain data for a book. Know if there is

a copy to borrow.

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Problem: Set the time of a watch

• Pressing the “mode”-button of the watch will raise the event “modeButton”

• Pressing button “inc” of the watch will raise the event “inc”

• The call event modeButton is used to go between states, and the call event inc is used to increment hours in state SetHours and minutes in state SetMinutes.

• Problem: Draw the state chart diagram.

DigitalWatch

+modeButton()

+inc()

-state: enum{Display,SetHours,SetMinutes}

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Solution: DigitalWatch

Display SetHours SetMinutes

modeButton()

modeButton() modeButton()

inc() inc()

state event

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More Info: DigitalWatch


do/display

current time

do/display

hours

do/display

minutes

modeButton()


inc()/hours:=

hours+1 modulo 24

inc()/minutes:=

minutes+1 modulo 60

DigitalWatch

modeButton() inc()

state

activity

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Compartments • Simple state chart describing how a password entry widget

works:

Enter Password

entry / set echo invisible

exit / set echo normal

do / blink cursor

character / handle character

help / display help

Name compartment

Internal activities

compartment,

contain also actions

Internal transition

compartment

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Internal Actions

Borrowed

entry/book.

borrowed(self)

On the shelf

entry/book.

returned(self)

return()

borrow()

Borrowed

exit/book.

returned(self)

On the shelf

exit/book.

borrowed(self)

return()

borrow()

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Internal Events

Working on Document

entry/open document

exit/close document

Working on Document

entry/open document

exit/close document

modify/commit modification

modify/commit modification

Internal event. Does not

cause “entry” or “exit”.

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Events • Call events

– All examples so far have been call events

• Time events

• Change events

• Signal events

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Time Event

On

first floor

Moving up

do/moving

to floor

Idle, not first fl.

Moving down

do/moving to

floor

arrived

arrived [floor>1]

go down(floor)

go up(floor)

after(20 sec)/go down(1)

go up(floor)

Time event

arrived [floor=1]

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Change event

On

first floor

Moving up

do/moving

to floor

Idle not first fl.

do/increase

timer

Moving down

do/moving to

floor

arrived

arrived[floor>1]

go down(floor)

go up(floor)

timer = timer-out /go down(first floor)

go up(floor)

Change event

arrived [floor=1]

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Signal

<<signal>>

RejectedWithDrawal

date:Date

accountNumber:String

requestAmount:double

availableBalnace:double

Some of the following examples are taken from:

UML 2 and The Unified Process

Arlow and Neustadt

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Signal events(1)

InCredit

deposit(m)/balance=balance+m

balance>=10000/notifyManager()

RejectingWithdrawal

entry/ logRejectedWithdrawal() AcceptingWithdrawal

entry/ balance=balance-m

withdraw(m)

[balance >= m]

withdraw(m)

[balance < m]

RejectedWithdrawal

close()

SimpleBankAccount

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Signal events(2)

processRejectedWitdrawal(a:RejectedWithdrawal)

Calling customer

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Connection transition

OnLoan Terminated

Overdue FineDue

after(

maximumDuration)

returnBook

[!extended]

returnBook

[extended]

loan

payFine

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Branching Transitions

Unpaid

OverPaid FullyPaid PartiallyPaid makeRefund

[payment<balance]

[payment=balance]

[payment>balance]

acceptPayment

BankLoan

acceptPayment

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Composite states

Accepted

Under treatment

Pre-treatment

Post-treatment

accept patient

treat patient

Surgery

incoming call/defer

Pay bill

Hospital

interrupt

Suspended treatment

restart

treatment

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Shallow history

Accepted

Under treatment

Pre-treatment

Post-treatment

accept patient

treat patient

Surgery

incoming call/defer

Pay bill

Hospital

interrupt

Suspended treatment

continue

treatment

H

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States with Substates

State1 State2 Staten a b c

State1 State2 Staten b c

finish finish finish

finish

Can be written as:

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Composite State

• If region one finishes, then that region will terminate, but region two will continue to execute.

• In this case, if region one terminates first, the whole composite state will stop executing.

Region 1

Region 2

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Example

Exercise 1 Exercise 2 exercise done exercise done

Term Project project done

exam pass

Failed

Studying

CourseAttempt

fail

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Constructing State Machines

Draw and name the states you know.

Write a comment: what does this state mean?

Draw the transitions you know, into or out of each state.

Do incomplete transitions suggest missing states?

Define and name the known events.

Assign an event to each transition; any missing events?

Do events need to carry event data?

Check for completeness; add discovered states/transitions.

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BridgePoint statchart • To make BridgePoint state charts executable they have been

simplified, so a state only contains:

• <transition> ::= <trigger> [„/‟action]

• Both in entry and on transition one can use the OAL. You will see example on this on Thursday.

State name

entry / action

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Checking for completeness

An automatic garage door: two buttons – up & down – and position sensors

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Filling the State Transition Table

States

Events Entry Action

What do the empty cells mean?

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A note on initial and final states • When an instance of a class is synchronously created, it

is placed in its initial state – It has not 'transitioned' into that state – so the

'entry' state action is not executed – An event assigned to a 'reflexive' transition can

trigger execution of the action – The initial state is the lowest numbered state

• A state machine may have one or more states with no outgoing transitions

– Obviously, when such a state is entered, the lifecycle can never proceed further

– The state can be marked as 'final„: after completing the state action, the instance will delete itself.

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Comments • Most of the slides in this lecture is produce by me, but some

slides is borrowed from Mentor Graphics and the book “UML 2 and The Unified Process” (Arlow and Neustadt)

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Appendix

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Withdraw Money Only main flow:

• user identifies himself by a card

• system reads the bank ID and account number from card and validates them

• user authenticates by PIN

• system validates that PIN is correct

• user requests withdrawal of an amount of money

• system checks that the account balance is high enough

• system subtracts the requested amount of money from account balance

• system returns card and dispenses cash

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Alternative Flow

8-10a: Not enough money on account: 1. System does not change the account

2. System returns card

…

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System Sequence Diagram Withdraw Money

insertCard(card)

givePin(userPin1)

giveAmount(amount)

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State Chart for Withdraw

CardInserted

gotCardPin

gotWrongPinOnce

gotWrongPinTwice

gotWrongPinThrice

gotRightPin

/cardPin=card.getPin()

givePin(userPin1)

[userPin1=cardPin]

givePin(userPin1)

[userPin1<>cardPin]

givePin(userPin2)

[userPin2=cardPin]

givePin(userPin2)

[userPin2<>cardPin]

givePin(userPin3)

[userPin3<>cardPin] givePin(userPin3)

[userPin3=cardPin]

/complain,keep card

giveAmount

(amount)

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Continue giveAmount

(amount)

gotRequestedAmount

gotCustomerID

gotBalance

finishedTransaction

insufficentBalance

/id:=card.getID()

/balance:=getBalance(id)

sufficientBalance

[balance>=amount]

Debit(id,amount)

/giveOutCash(amount)

/notifyInsufientBalance()

/retunrCard()

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State Charts

Bottle

capacity:Integer

contents:Integer

fill(amount:Integer)

Cap 0..1 0..1

empty partiallyFilled

filled

capped


[amount<capacity]


[contents+amount<capacity]


[contents+amount>=capacity]


[amount>=capacity]

[contents = capacity]

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empty partiallyFilled

filled

capped


[amount<capacity]


[contents+amount<capacity]


[contents+amount>=capacity] fill(amount:Integer)

[amount>=capacity]

contents = capacity

Making Contract context Bottle::fill(amount:Integer)

pre: not filled and not capped

post: (partiallyFilled and

content@pre + amount < capacity)

or

(filled and contents@pre + amount >= capacity)

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Code: DigitalWatch


do/display

current time

do/display

hours

do/display

minutes

modeButton()


inc()/hours:=

hours+1 modulo 24

inc()/minutes:=

minutes+1 modulo 60

DigitalWatch

modeButton() inc()

state

activity

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State

public class State{

public final int Display = 1;

public final int SetHours = 2;

public final int SetMinutes = 3;

public int value;

}

DigitalWatch

+ modeButton()

+ inc()

State

+ Display : int = 1 {frozen}

+ SetHours : int = 2 {frozen}

+ SetMinutes : int = 3 {frozen}

+ value : int

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public class DigitalWatch{

private State state = new State();

private DigitalDisplay LCD = new DigitalDisplay();

public DigitalWatch(){

state.value = state.Display;

LCD.displayTime();

}

public void modeButton() { … }

public void inc() { … }

}

DigitalWatch

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ModeButton public void modeButton() { switch (state.value){ case state.Display : LCD.displayTime(); state.value = state.SetHours; break; case state.SetHours: LCD.displayHours(); state.value = state.SetMinutes; break; case state.SetMinutes: LCD.displayTime(); state.value = state.Display; break; } }

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Inc public void inc() {

switch (state.value){

case state.Display : break;

case state.SetHours: LCD.incHours();

break;

case state.SetMinutes: LCD.incMinutes();

break;

}

}

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Design Pattern: State

DigitalWatch

+ modeButton()

+ inc()

State

Display

+inc()

Hours

+inc()

Minutes

+inc()

+inc()

Comment:

This is more object oriented!

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Two examples to show the power of state charts

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The life cycle of an applet

init

start

stop

destroy

Loading

applet

Leaving

page Visiting

page

Discarding

page

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Thread states

New Thread Dead

yield

start

The run method terminates

sleep

(finish sleeping)

wait

notify

I/O finish

public final boolean isAlive()

A thread is alive if it is in the state ”Runnable” or ”Blocked” .

Blocked

Wait to be

notified

Wait for target

to finish

Wait for I/O

Sleeping

Runnable

Not

interrupted

interrupted

join

target finish blocked on I/O

Alive

interrupt

interrupt()/throws InterruptedException

Documents

Object Oriented System Development Lecture 7 Classes ... · Rogardt Heldal Classes, Objects, and Relations - 3 - Mapping to code • One can map a UML class to many different code