Lecture 2: UML Class DIAGRAM

LECTURE 2:UML CLASS DIAGRAM

CSC 213 – Large Scale Programming

Today’s Goal

Learn Unified Process to design programs Understand what are the “types” of Java

classes Methods of selecting the potential classes How these designs presented for others to

use

Classroom Development

Always start from scratch Know all requirements from the start

And requirements will not change Coding begins immediately at start

Projects are trivial jokes in real-world If lasts 15 weeks, project “large scale”

Code cannot be reused Never look at again, anyway

Why These Phases Matter

Our Goal

Our Nemesis

Other Nemesis

Other Nemesis

Where We Start

Find the Classes

Designing classes next step in process Could help find & fix inconsistent

requirements Requirements clarified if you do not

understand them Outlining classes makes coding easy

Already know methods to call from other classes

Will provide chance to do some easy debugging

Noun Extraction

Finds entity class candidates to be used in design Initial pass may (will) not find all entity

classes Some classes not used even though found

early on Provides strong hints for other needed

classes Start with plain English requirements

Should be easy & comes with most assignments

Many nouns not needed, so can prune list Eliminate any & all classes external to

program

Designing Elevator Controller

Buttons in elevators and on the floors control the movement of n elevators in a building with m floors. Buttons illuminate when pressed to request the elevator stop at a specific floor; the illumination is canceled when the request has been satisfied. When an elevator has no requests, it remains at its current floor with its doors closed.

Noun Extraction

1. Underline the nouns in the requirementsButtons in elevators and on the floors control the movement of n elevators in a building with m floors. Buttons illuminate when pressed to request the elevator stop at a specific floor; the illumination is canceled when the request has been satisfied. When an elevator has no requests, it remains at its current floor with its doors closed.

1. Underline the nouns in the requirementsButtons in elevators and on the floors control the movement of n elevators in a building with m floors. Buttons illuminate when pressed to request the elevator stop at a specific floor; the illumination is canceled when the request has been satisfied. When an elevator has no requests, it remains at its current floor with its doors closed.

Noun Extraction

2. Eliminate nouns external to the problemButtons in elevators and on the floors control the movement of n elevators in a building with m floors. Buttons illuminate when pressed to request the elevator stop at a specific floor; the illumination is canceled when the request has been satisfied. When an elevator has no requests, it remains at its current floor with its doors closed.

Noun Extraction

2. Eliminate nouns external to the problemButtons in elevators and on the floors control the movement of n elevators in a building with m floors. Buttons illuminate when pressed to request the elevator stop at a specific floor; the illumination is canceled when the request has been satisfied. When an elevator has no requests, it remains at its current floor with its doors closed.

Noun Extraction

3 “Types” of Classes

Unified Process concept simplifies design process Entity classes hold long-lived data driving

program Input & output handled by boundary

classes Control classes do complex processing in

program "Types" not real, exist for design

purposes only A class is a class is a class within Java &

program But they can help checking design covers all

needs

Entity Classes

Entity Classes

Focus on entity classes & ignore (for now) others Since not things, prune abstract (non-

physical) nouns Ignore if used for communication – rarely

drive program Thinking will change -- must work

iteratively Writing & debugging easier given good design Minutes spent in design saves hours in coding

& testing

“Must work iteratively” !=


Find Entity Classes

1. Ignore abstract (non-physical) nounsButtons in elevators and on the floors control the movement of n elevators in a building with m floors. Buttons illuminate when pressed to request the elevator stop at a specific floor; the illumination is canceled when the request has been satisfied. When an elevator has no requests, it remains at its current floor with its doors closed.

Find Entity Classes

1. Ignore abstract (non-physical) nounsButtons in elevators and on the floors control the movement of n elevators in a building with m floors. Buttons illuminate when pressed to request the elevator stop at a specific floor; the illumination is canceled when the request has been satisfied. When an elevator has no requests, it remains at its current floor with its doors closed.

Find Entity Classes

2. Only use singular form of each nounButtons in elevators and on the floors control the movement of n elevators in a building with m floors. Buttons illuminate when pressed to request the elevator stop at a specific floor; the illumination is canceled when the request has been satisfied. When an elevator has no requests, it remains at its current floor with its doors closed.

Find Entity Classes


Find Entity Classes


Button Floor Elevator

Our Entity Classes

Boundary Classes

These classes will perform all input & output May have many details which are all

independent Only 1 detail known: it will change before

its over Make class for each detail & limit future

rewriting Make life easier, start from simplest

ideas Easy to combine simple classes to create

complex ones Taking a complex class and breaking up far

harder Rarely rewrite complex classes because of

difficulty…… instead often just throw out & start from scratch

Skipping Boundary Classes

Boundary classes may duplicate primitive type Can eliminate this class; it adds nothing to

design Code will have primitive hard-coded

everywhere Saves writing javadoc for class, field, getter

& setter When needs change and class now

needed…






needed… Find & replace all primitives littering code Scan entire program to track down all I/O

for this data Retest entire application to ensure now

bugs created






needed… Find & replace all primitives littering code Scan entire program to track down all I/O

for this data Retest entire application to ensure now

bugs created Industry usually finds better writing

class at start

1. Reexamine abstract nouns & keep if used in I/OButtons in elevators and on the floors control the movement of n elevators in a building with m floors. Buttons illuminate when pressed to request the elevator stop at a specific floor; the illumination is canceled when the request has been satisfied. When an elevator has no requests, it remains at its current floor with its doors closed.

Find Boundary Classes

1. Reexamine abstract nouns & keep if used in I/OButtons in elevators and on the floors control the movement of n elevators in a building with m floors. Buttons illuminate when pressed to request the elevator stop at a specific floor; the illumination is canceled when the request has been satisfied. When an elevator has no requests, it remains at its current floor with its doors closed.




3. Buttons in elevators and on the floors control the movement of n elevators in a building with m floors. Buttons illuminate when pressed to request the elevator stop at a specific floor; the illumination is canceled when the request has been satisfied. When an elevator has no requests, it remains at its current floor with its doors closed.


3. There is no step 3Buttons in elevators and on the floors control the movement of n elevators in a building with m floors. Buttons illuminate when pressed to request the elevator stop at a specific floor; the illumination is canceled when the request has been satisfied. When an elevator has no requests, it remains at its current floor with its doors closed.Movement Request Illumination

I Know Boundary Classes!

Control Classes

Non-obvious algorithms using many classes Rule of thumb: obvious algorithm have

name Control classes already exist for named

algorithms Needed for those plurals ignored

previously Can use array or enum, if exact number

known Else, design needs structure to hold

instances

Control Classes





known Else, design needs data structure to hold

instances

Control Classes





known Else, design needs data structure to hold

instances CSC212 & CSC213 focus: future control

classes CSC213 will discuss many “obvious”

algorithms Important data structures developed in both

courses

1. Reexamine plurals & keep when necessaryButtons in elevators and on the floors control the movement of n elevators in a building with m floors. Buttons illuminate when pressed to request the elevator stop at a specific floor; the illumination is canceled when the request has been satisfied. When an elevator has no requests, it remains at its current floor with its doors closed.

Finding Control Classes!

1. Reexamine plurals & keep when necessaryButtons in elevators and on the floors control the movement of n elevators in a building with m floors. Buttons illuminate when pressed to request the elevator stop at a specific floor; the illumination is canceled when the request has been satisfied. When an elevator has no requests, it remains at its current floor with its doors closed.


2. Eliminate if constant number (array) neededButtons in elevators and on the floors control the movement of n elevators in a building with m floors. Buttons illuminate when pressed to request the elevator stop at a specific floor; the illumination is canceled when the request has been satisfied. When an elevator has no requests, it remains at its current floor with its doors closed.






3. Select data structure to use for each pluralButtons in elevators and on the floors control the movement of n elevators in a building with m floors. Buttons illuminate when pressed to request the elevator stop at a specific floor; the illumination is canceled when the request has been satisfied. When an elevator has no requests, it remains at its current floor with its doors closed.


3. Select data structure to use for each pluralButtons in elevators and on the floors control the movement of n elevators in a building with m floors. Buttons illuminate when pressed to request the elevator stop at a specific floor; the illumination is canceled when the request has been satisfied. When an elevator has no requests, it remains at its current floor with its doors closed.

PriorityQueue


Now Determine Fields in Design Designing classes next step in process

For each class, determine fields Link classes that work together so easy to

code When done well, coding becomes relatively

simple What should be fields & how can we

know? Since they are abstract, boundary classes

often fields Control classes often fields; something

must use it Read text again: look where one noun

posses another

What To Do Next?

Must communicate design in clear way to others Make explicit what the classes for this

program are Identify fields & other relationships

between classes Make certain information is clearly

highlighted Provides vital check that can often find

bugs Will do this by drawing pretty pictures

What To Do Next?

Must communicate design in clear way to others Make explicit what the classes for this

program are Identify fields & other relationships

between classes Make certain information is clearly

highlighted Provides vital check that can often find

bugs Will do this by drawing pretty pictures

Pictures Worth 1,000 Words



Why Draw Classes?

Pictures used to share ideas easily Gets everyone up & coding at once

Group spends lab watching you code… …or get suckers to work while you relax

Why Draw Classes?


Group spends lab watching you code… …or get suckers teammates to work while

you relax

Why Draw Classes?


Group spends lab watching you code… …or get suckers teammates suckers to work while

you relax

Why Draw Classes?



you relax Even better to get suckers working in

parallel

Why Draw Classes?




parallel

Why Draw Classes?




parallel Methods & their signatures included in

diagrams Can write code using all classes, even if

unwritten

UML Class Diagrams

Classes drawn in 3-part box Class name written in top portion of box Attributes (fields) written in middle

portion Operations (methods) written in bottom

portion All variables written using following

format :name : type

Draw all important relationships within classes Inheritence & important fields normally

shown here Solid lines for classes and dashed lines for

interfaces

Drawing Relationships

Must be able to explain all relationships

Drawing Relationships

Must be able to explain all relationshipsBoyfriend-Girlfriend

Just FriendsFriends “with benefits”Sweeties Married

Best Friends

Relationships From Fields

Aggregation Used for collection whose instances do not

rely on source Car aggregates CarParts (e.g., tires, engine,

lights…) Composition

Use when objects from target used only within source

Chessboard composes Squares Association

Source object has field of target type (not a collection)

Often used to imply source calls target's methods

Playing “Utah Hold’Em”?

All of above relationships must be labeled Give field a name & show it near midpoint

of arrow Monogamous? Poly? Specify numbers

involved Each end of link has number involved on

that end Could be some range of numbers like ‘2..5’ + means 1 of more objects required to be

used Use Kleene’s star ‘*’ for 0 or more objects Specific number (1, 42, 69) good if

specifically known

Generalization (“inheritance”) Shows subclass-superclass relationship Does not involve fields, multiplicities, or

anything else Makes this a different type of connection

than others Must draw all generalizations within the

diagram For implementation to be correct, these are

critical

Other Type of Connections

Our “Final” Design Decisions


Elevator's UML Class Diagram

Note that Button class serves two purposes Direct travel to specific floor if in an

elevator Used on a floor to request travel up or

down Much easier with 2 subclasses of Button



2m-2 DirectionalButtons talk to n Elevators? But only 1 should respond; never use n-to-m

connection Who handles Requests? Need new class for

this!


Next: where do methods come from?

For Next Lecture

Link to article for Monday on lecture page Reading for Monday available on Angel

What else can we do before coding? Are there more tricks that enables our

laziness? How to trick smarter suckers into doing our

work? Weekly assignment problem due in class

Mon. Weekly assignment page has problem for

today Noun extraction to find entity, boundary, &

control classes Show the connections by drawing UML class

diagram

Lecture 2: UML Class DIAGRAM

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