lecture 2: uml class diagram
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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” !=
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.
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
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
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.
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…
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… 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
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… 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.
Find Boundary 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 Boundary Classes
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.
Find Boundary Classes
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
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 data structure to hold
instances
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 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.
Finding Control Classes!
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.
Finding Control Classes!
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.
Finding Control Classes!
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.
Finding Control Classes!
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.
Finding Control Classes!
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
Finding Control Classes!
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
Pictures Worth 1,000 Words
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?
Pictures used to share ideas easily Gets everyone up & coding at once
Group spends lab watching you code… …or get suckers teammates to work while
you relax
Why Draw Classes?
Pictures used to share ideas easily Gets everyone up & coding at once
Group spends lab watching you code… …or get suckers teammates suckers to work while
you relax
Why Draw Classes?
Pictures used to share ideas easily Gets everyone up & coding at once
Group spends lab watching you code… …or get suckers teammates suckers to work while
you relax Even better to get suckers working in
parallel
Why Draw Classes?
Pictures used to share ideas easily Gets everyone up & coding at once
Group spends lab watching you code… …or get suckers teammates suckers to work while
you relax Even better to get suckers working in
parallel
Why Draw Classes?
Pictures used to share ideas easily Gets everyone up & coding at once
Group spends lab watching you code… …or get suckers teammates suckers to work while
you relax Even better to get suckers working in
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
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.
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
Elevator's UML Class Diagram
Elevator's UML Class Diagram
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!
Elevator's UML Class Diagram
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
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