Outline of this exercise
• Learning objectives of the tutorial:
– After this exercise, a student should be able to:
•
•
•
•
Read and create UML class diagrams
Describe the basic process for developing a UML class diagram
Explain what is easy about the process and what is hard
Explain the iterative nature of the design process
• Process:
– Review the specification of BallWorld
– Develop a UML class diagram for BallWord
• Together (in groups), step by step
• Review the sample solution, and invent your own version of the
model before our next class (to turn in) – use handout as a template
(see the last slide in this presentation )
Fundamentals of Software
Development 1
Slide 1
Specification of BallWorld
• BallWorld is just that -- a world
that contains various kinds of
balls
– along with hotspots and perhaps
other things eventually
• Each of the buttons
represents a Java class that
you will write
– Pressing a button creates a ball
of that type
• Types of Balls might include:
– Dud: does nothing
– DudThatMoves: just moves
in a constant, random velocity
– Bouncer: like a Mover, but bounces off the walls of
– Dragger: the user can drag it
the World
around and kill (delete) it
– Shrinker: A Bouncer that grows and shrinks in size
– Mover: like a Dragger, but
– Exploder: Grows, then explodes and replicates itself!
moves like a MovingDud
Questions? You cannot design software
Fundamentals of Software
Development 1
Slide 2
unless you know what it is supposed to do!
Design BallWorld, by drawing a
UML class diagram for it
Review the specification, then:
1. Identify kinds of objects – these become classes
2. Identify relationships between classes
•
•
is-a (extends), is-a (implements), has-a
Identify interfaces that specify what is needed for the
classes to relate
3.
For each class, determine its attributes and
4.
For each class, for each attribute/operation,
determine its type
operations
Fundamentals of Software
Development 1
Slide 3
List the classes
in BallWorld
• List the kinds of
things – classes –
that you think
belong in the
BallWorld design:
– Some are visual
– Some are internal
– Some are relevant
Java library classes
like JFrame
Fundamentals of Software
Development 1
• When done,
compare your list
with other lists
around the room
Slide 4
The classes I chose –
without thinking
about Java
• Visual things:
– BallWorldFrame
• Where everything
gets displayed
– BallButton
• A single class, with
several instances
with different labels
• Relevant Java library
classes:
– ?
Fundamentals of Software
Development 1
• Non-visual things:
– BallWorld
• The class that contains main and starts the
program. (Ok, I thought about Java after all!)
– Ball
– Various subclasses of Ball
– HotSpot
Slide 5
The classes I chose –
knowing Java
• Visual things:
–
–
–
–
BallWorldFrame
WorldPanel
ButtonsPanel
BallButton
• A single class, with
several instances
with different labels
• Relevant Java library
classes:
– JFrame
– JPanel
– JButton
Question:
Why not just let the
Fundamentals of Software
WorldPanel
Development 1play this role?
• Non-visual things:
– BallWorld
• The class that contains main
–
–
–
–
Ball
Various subclasses of Ball
HotSpot
World
Answer: I
choose to
separate
function
from display
of that
function
Slide 6
• The class that manages all the Balls and HotSpots
Where we are in the process…
Design BallWorld, by drawing a
UML class diagram for it
We just did our first
Review the specification, then:
iteration of Step 1
1. Identify kinds of objects – these become classes
2. Identify relationships between classes
•
•
is-a (extends), is-a (implements), has-a
Identify interfaces that specify what is needed for the
classes to relate
3.
For each class, determine its attributes and
4.
For each class, for each attribute/operation,
determine its type
operations
Fundamentals of Software
Development 1
Now we’ll do our first iteration of Step 2,
beginning with the is-a (extends) relationship
Slide 7
Likely Is-a
relationships
JButton
BallButton
JFrame
ButtonsPanel
JPanel
BallWorldFrame
Draw the is-a relationships
between the classes shown
BallWorld
WorldPanel
Notation:
A
B
A is-a B, that is, A extends B
Ball
HotSpot
World
Please draw along on your
handout, and ask questions!
(Use pencil.)
Fundamentals of Software
Development 1
This means that A inherits all
the attributes (data) and
operations (behaviors) of B
Questions on is-a so far?
Slide 8
More Is-a
relationships
• Types of Balls might include:
– Dud: does nothing
– MovingDud: just moves in a
constant, random velocity
– Dragger: the user can drag it
around and kill (delete) it
– Mover: like a Dragger, but
moves like a MovingDud
Ball
– Bouncer: like a Mover, but bounces off the walls of
the World
– Shrinker: A Bouncer that grows and shrinks in size
– Exploder: Grows, then explodes and replicates itself!
Draw possible is-a relationships
between the types of Balls
Mover
Notation:
Dud
Dragger
MovingDud
Fundamentals of Software
Development 1
Bouncer
Shrinker
Exploder
...
A
B
A is-a B, that is, A extends B
This means that A inherits all the
attributes (data) and operations
(behaviors) of B
Questions on is-a
relationships?
Slide 9
Likely Has-a
relationships
JButton
BallButton
JFrame
ButtonsPanel
JPanel
BallWorldFrame
Draw possible has-a relationships in
which objects are created, for the
classes shown
BallWorlds
WorldPanel
Notation:
A
B
A has-a B, here, A creates a B
Ball
HotSpot
Indicate the multiplicity on each end:
World
I also use color (here, lime green, but more often I use
red) to indicate has-a relationships that involve object
creation. This is not standard UML.
Fundamentals of Software
Development 1
1 .. * (one or more)
3
(exactly 3)
(blank often means 1)
Slide 10
Has-a
JButton
relationships
BallButton
7..*
JFrame
ButtonsPanel
JPanel
BallWorldFrame
Notation:
A
B
A has-a B, here, A creates a B
BallWorlds
WorldPanel
Ball
HotSpot
1..*
World
Indicate the multiplicity on each
end: 1 .. * (one or more), blank
for exactly 1
Part of an answer: I envision a
single frame, but possibly many
Worlds and associated Panels.
Do you see why that leads to
my choices?
I chose to have the BallWorlds
create each World, which creates the
two panels (WorldPanel and
ButtonPanel). Why? Who else
might I have chosen to create the
At this point, we have a problem – what remains
Fundamentals of Software
World?
The
Panels?
Development 1
to be created? Who should create them?Slide 11
Has-a
JButton
relationships
BallButton
7..*
JFrame
ButtonsPanel
JPanel
BallWorldFrame
Notation:
A
B
A has-a B, here, A creates a B
BallWorld
WorldPanel
Ball
We have yet to create
the Balls and HotSpots?
Who should create the
HotSpots?
Fundamentals of Software
Development 1
HotSpot
0..*
1..*
Indicate the multiplicity on each
end: 1 .. * (one or more), blank
for exactly 1
World
Answer: the World seems a natural choice.
Who creates a new Ball, e.g., a new Exploder? How?
Answer: the human user, by pressing a BallButton.
Slide 12
Has-a
JButton
relationships
BallButton
7..*
JFrame
ButtonsPanel
JPanel
BallWorldFrame
Notation:
A
B
A has-a B, here, A creates a B
BallWorld
WorldPanel
Ball
HotSpot
0..*
1..*
Indicate the multiplicity on each
end: 1 .. * (one or more), blank
for exactly 1
World
So the human user creates each Ball (e.g. an Exploder), by pressing a BallButton.
When the human presses a BallButton, a Ball of the appropriate type must be:
Constructed
Added to the World
Drawn
In the current design, the latter two are impossible. Explain.
Fundamentals of Software
Development 1
Slide 13
Has-a
JButton
relationships
BallButton
7..*
JFrame
ButtonsPanel
JPanel
BallWorldFrame
Notation:
A
B
A has-a B, here, A creates a B
BallWorld
WorldPanel
Ball
HotSpot
0..*
1..*
Indicate the multiplicity on each
end: 1 .. * (one or more), blank
for exactly 1
World
So the human user creates each Ball (e.g. an Exploder), by pressing a BallButton.
When the human presses a BallButton, a Ball of the appropriate type must be:
Constructed
Added to the World
Drawn
In the current design, the latter two are impossible. Draw the has-a relationships that are
needed
– who
needs to know whom? These are has-a relationships, but do NOT involve
Fundamentals
of Software
Development
Slide 14
creation
of 1objects. How are these relationships going to be implemented?
is-a
has-a
JButton
Relationships
JFrame
1..*
BallButton
1..*
ButtonsPanel
JPanel
BallWorldFrame
1..*
Draw links to enable the
construct/add/draw actions.
Revise your answers to the
“who-should” questions as
needed, as you design.
Dud
Fundamentals of Software
Development 1
• Constructed
WorldPanel
BallWorld
1..*
Bouncer
When a new Ball is created,
it must be:
World
Ball
Bloater
• Added to the World
• Drawn
Who should construct the
Ball? Add it to the World?
Draw it?
Exploder
...
Slide 15
is-a
has-a
JButton
Relationships
JFrame
BallButton
1..*
ButtonsPanel
1..*
JPanel
BallWorldFrame
1..*
WorldPanel
BallWorld
1..*
BallButton: construct the new
Ball. No links needed. (Why?)
BallButton: tell the World to add
the Ball. What does that imply is
needed in the diagram?
Dud
Fundamentals of Software
Development 1
Bouncer
World
Draw links to enable the
construct/add/draw actions.
Revise your answers to the
“who-should” questions as
needed, as you design.
Here are my decisions, as I
made them.
Ball
Bloater
Exploder
...
Slide 16
is-a
has-a
JButton
Relationships
JFrame
1..*
BallButton
1..*
ButtonsPanel
JPanel
BallWorldFrame
1..*
BallWorld
• BallButton must have the World
WorldPanel
1..*
BallButton: construct the new
Ball. No links needed.
How does the BallButton
obtain the World?
BallButton: tell the World to add
the Ball. Hence:
World
• World must be able to add a Ball
What has-a relationships does that
imply need to be added, for the
BallButton to have the World?
Ball
Answer: BallWorldFrame
creates
the World,Bloater
then sends it to
the ButtonsPanel,
Dud
Bouncer
Exploder
. . . who
Fundamentals
of Software
sends
it to each
BallButton. Do you see why it was a good decision for
Development 1
Slide 17
BallWorldFrame to create the 3 big things?
is-a
has-a
JButton
Relationships
JFrame
1..*
BallButton
1..*
ButtonsPanel
JPanel
BallWorldFrame
1..*
BallWorld
• BallButton must have the World
WorldPanel
1..*
BallButton: construct the new
Ball. No links needed.
How does the BallButton
obtain the World?
BallButton: tell the World to add
the Ball. Hence:
World
• World must be able to add a Ball
What has-a relationships does that
imply need to be added, for the
BallButton to have the World?
Ball
Answer: BallWorldFrame
creates
the World,Bloater
then sends it to
the ButtonsPanel,
Dud
Bouncer
Exploder
. . . who
Fundamentals
of Software
sends
it to each
BallButton. Do you see why it was a good decision for
Development 1
Slide 18
BallWorldFrame to create the 3 big things?
is-a
has-a
JButton
Relationships
JFrame
1..*
BallButton
1..*
ButtonsPanel
JPanel
BallWorldFrame
1..*
WorldPanel
BallWorld
When a new Ball is created,
it must be:
1..*
Who creates a new Ball,
e.g., a new Exploder? How?
Answer: the human user, by
pressing a BallButton.
Dud
Fundamentals of Software
Development 1
The World is intended to hold
all of the balls. What has-a
does that imply? Draw it.
Bouncer
World
1..*
Ball
Bloater
• Constructed
• Added to the World
• Drawn
In the current design, some
ofExploder
this is impossible.
...
Explain.
Slide 19
is-a
has-a
JButton
Relationships
JFrame
1..*
BallButton
1..*
ButtonsPanel
JPanel
BallWorldFrame
Drawable interface
1..*
BallWorld
Animatable interface
WorldPanel
WorldManagement interface
1..*
World
1..*
Ball
Dud
Fundamentals of Software
Development 1
Bouncer
What about interfaces? – This
is a chance to give the design
strategic consistency by
Bloater defining
Exploder
..
up front how .the
20
interacting entities shouldSlide
talk!
More questions
• Attributes: What does a Ball have?
• When the human user clicks a BallButton, should the World
become aware of the constructed Ball? If so, how?
• How is drawing done?
– WorldPanel gives info to Ball, or Ball gives info to WorldPanel?
• How do Balls “act”? What else should the human user be able
to do to Balls? How is that accomplished?
• Who should act independently (i.e., what threads should exist)?
• What interfaces would be useful in the above? In particular,
what should the following be able to do:
– Ball
Fundamentals of Software
Development 1
HotSpot
ManagerOfBalls
ManagerOfHotSpots
Homework – Finish this tutorial and your drawing.
Put your name on it – and on the back explain what
you did differently! We’ll discuss next class…
Slide 21