1. From Design To Code Oct 25, 2006

2. Recap: Class Diagrams Class diagrams represent design structure
Three parts: name, attribute, operations
Visibility, attribute type, multiplicity
Association, association multiplicity
Generalization i.e. interface impl, subclassing
Composition i.e. class A contains class B
Applied information hiding, DSM, layering

3. Recap: Interaction Diagrams
Represent functionality
Two major parts:
Life line boxes (represent life time of an object)
Messages between objects (instances)
Also looked at some special case notations
Instances: parameterized instances, singleton instances, array elements
Messages: creation, destruction, conditional messages, mutually exclusive conditional messages, asynchronous messages, polymorphic messages
Abstractions: looping, iteration over collection, nesting of frames, decomposition

4. Today’s Lecture Interaction Diagrams Basics & Notations
Responsibility Assignment Principles

5. Example: Switch-Motor System
Scenario: Motor can run, when the Switch state is on
Class list: Switch and Motor
R1: Store the decision condition
R2: Make a decision
R3: Run the motor

6. Class Diagram View Switch Motor -state:bool -switch:Switch1
-state:bool
-switch:Switch
switch
+getState():bool
+run()
Class Diagram: three parts – class name, attributes, and operations
The first part may also contain stereotypes.

7. Interaction Diagram View
:Motor
Lifeline boxes
switch:Switch
run
getState
state
:Motor represents unnamed instance of class motor
switch:Switch represents named instance of class Switch
Another examples in the book are paremeterized that are written ArrayList <int>, if you were to use generics in your homework 3.
ith element in the array “arr” of type IntArray would be written arr[i]: IntArray
In case of a singleton, i.e. a class that only has a single instance in the application domain, we would write a 1 in the top right corner.
How would you show creation? Figure in book
How would you show destruction? Figure in book
How would you show looping? (Remember from sequence diagram example) Figure in book
How would you show conditional messages? Figure in book
How would you show mutually exclusive conditional messages? Figure in book
How would you show iteration over a collection ? Figure in book
How would you show nesting of frames? Example in Figure shows looping, when a certain condition is true.
How would you decompose a larger interaction diagram? Figure shows one way. Also, remember from the sequence diagram examples. Essentially the same technique.
How would you show polymorphism? Figure in book.
How would you show asynchronous calls? Figure in book.

8. Switch-Motor: CRC Card View
Scenario: Motor can run, when the Switch state is on
Class list: Switch and Motor
R1: Store the decision condition, R2: Make a decision, and R3: Run the motor
Class Name: Switch
Subclasses:
Super classes:
Responsibilities Collaborators
Store decision
condition
Class Name: Motor
Subclasses:
Super classes:
Responsibilities Collaborators
Make a decision Switch
Run the motor
Notice that the Switch is the collaborator of Motor, but not vice versa.
Question: What is the coupling relationship in this case?

9. Class Diagram View Switch Motor -state:bool -switch:Switch1
-state:bool
-switch:Switch
switch
+getState():bool
+run():void
void run(){
if(switch.getState()){ /* Make a decision */
/* run the motor */ }

10. Impact of Change: Multi-State Switch
Motor 1
-state:bool
-switch:Switch
-state:int
switch
+getState():bool
+run():void
+getState():int
void run(){
if(switch.getState()){ /* Make a decision */
/* run the motor */ }
Change: Switch can have more than two states.

11. Change Escapes Module Boundary
Switch
Motor 1
-state:bool
-switch:Switch
-state:int
switch
+getState():bool
+run():void
+getState():int
void run(){
if(switch.getState()){ /* Make a decision */
/* run the motor */ }
Change: Switch can have more than two states.
Impact of Change

12. Information Expert Which class has the necessary information?
Example – class list: Switch and Motor
R1: Store the decision condition, R2: Make a decision, and R3: Run the motor
Class Name: Switch
Subclasses:
Super classes:
Responsibilities Collaborators
Store decision
Condition
Make a decision
Class Name: Motor
Subclasses:
Super classes:
Responsibilities Collaborators
Run the motor Switch

13. Improved Class Diagram View
Switch
Motor 1
-state:bool
-switch:Switch
switch
+isOn():bool
+run():void
void run(){
if(switch.isOn()){
/* run the motor */ }

14. Implementation Changes Encapsulated
Switch
Motor 1
-state:bool
-switch:Switch
-state:int
switch
+isOn():bool
+run():void
+isOn():bool
void run(){
if(switch.isOn()){
/* run the motor */ }
Change: Switch can have more than two states.
Remember: Information Hiding

15. Example: User-Level Process Management
Main scenario: A process will maintain necessary information for it to run such as program counter (PC), reference to program segment (.ps), reference to data segments (.ds), registers (regs)
Scenario of interest: functionality to create an identical copy of a process should be provided
Class list: process, client
R1: store information PC, .ps, .ds. Regs
R2: create copy of process

16. User-Level Process Management : CRC Card View
Class list: process, client
R1: store information pc, .ps, .ds. regs
R2: create copy of process
Class Name: Process
Subclasses:
Super classes:
Responsibilities Collaborators
Store information
pc, .ps, .ds. regs
Class Name: Client …
Subclasses:
Super classes:
Responsibilities Collaborators
Create copy Process
of .pc, .ps, .ds,
.regs
Spawn another
process
Notice that the Switch is the collaborator of Motor, but not vice versa.
Question: What is the coupling relationship in this case?

17. Change: Register-based to Stack-based Machine
Class list: process, client
R1: store information pc, .stack, .top, .ps, .ds.
R2: create copy of process
Class Name: Process
Subclasses:
Super classes:
Responsibilities Collaborators
Store information
pc, .stack, .top,
.ds. regs
Class Name: Client …
Subclasses:
Super classes:
Responsibilities Collaborators
Create copy Process
of .pc, .ps, .ds,
.regs
Spawn another
process
Notice that the Switch is the collaborator of Motor, but not vice versa.
Question: What is the coupling relationship in this case?
Impact on all clients

18. Creator: Which class has the initializing data?
Class list: process, client
R1: store information pc, .ps, .ds. regs
R2: create copy of process
Class Name: Process
Subclasses:
Super classes:
Responsibilities Collaborators
Store information
pc, .ps, .ds. regs
Create copy of
.pc, .ps, .ds, .
regs and spawn
another process
Class Name: Client …
Subclasses:
Super classes:
Responsibilities Collaborators
Process
Notice that the Switch is the collaborator of Motor, but not vice versa.
Question: What is the coupling relationship in this case?
Change Impact Encap-sulated

19. Adding GUI to the Sorting Application
Integers (>0)
Sorting Algorithm
Merge Sort
: User
Sort
Which class should handle the Sort Event?
Class Name: UI
Subclasses:
Super classes:
Responsibilities Collaborators
Handle Sort SortingApp
Event
Class Name: SortingApp
Subclasses:
Super classes:
Responsibilities Collaborators
Create sorting, ISort, IStorage
storage instance etc.

20. Adding GUI to the Sorting Application
SortButton …
/addActionListener(ActionListener l)
javax.swing.DefaultButtonModel …
+addActionListener(ActionListener l)
SortingApplication
java.awt.event.ActionListener …
+actionPerformed(ActionEvent e)
storage:IStorage
sort:ISort
+sort(…):IStorage
/actionPerformed(ActionEvent e)

21. Summary Interaction Diagrams Responsibility Assignment Principles
Information Expert
Creator
Controller
Polymorphism
Pure Fabrication
Indirection
Protected Variations
Most of these principles are derivative of the information hiding principle that we have studied before.
In this lecture:
- Understand these principles through examples
Understand class and interaction diagrams on the way
Relate these principles to information hiding principle
Also, show examples of the CRC card process