1. Starting Object Design
Chapter 14
Starting Object Design

2. Spend time on dynamic models They are the key tool for building good static models

3. One Object Design Technique: Class Responsibility Collaboration (CRC) cards

4. CRC Card examples

5. Dynamic modeling of object: Interaction Diagrams
Chapter 15
Dynamic modeling of object: Interaction Diagrams

6. UML Interaction Diagrams
Two variants
Sequence diagrams
Communication diagrams

7. Example: Sequence Diagram

8. What does this represent in code?
public class A {
private B myB = new B();
public void doOne() {
myB.doTwo();
myB.doThree(); }

9. Example: Collaboration Diagram

10. Strengths and Weaknesses of Sequence and Collaboration Diagrams

11. Example Sequence Diagram
public class Sale {
private Payment payment;
public void makePayment(Money cashTendered) {
payment = new Payment(cashTendered);
// ... }

12. Example collaboration diagram
public class Sale {
private Payment payment;
public void makePayment(Money cashTendered) {
payment = new Payment(cashTendered);
// ... }

13. Lifeline boxes

14. Used if we want only ONE instance of a class instantiated
The Singleton Pattern
Used if we want only ONE instance of a class instantiated
Examples: Database, log
We’ll learn how to accomplish this in Java later

15. Lifelines, messages, “found” or “starting” messages

16. Illustrating Replies or Return Values
Two alternatives
Using the message syntax returnVar = message(parameter)
Use a reply or return message at the end of an activation bar

17. Messages to “self” or “this”

18. Instance Creation

19. Object Destruction (Object no longer used or usable)
Object explicitly destroyed or no longer usable (reachable)
Example: No variable refers to object any longer
Marked for garbage collection

20. Looping notation

21. A conditional message

22. UML Version 1 notation for conditional messages

23. Mutually exclusive conditional messages

24. Iteration over a collection: Explicit notation
Selector expression

25. Iteration over a collection: Implicit notation

26. Nested frames

27. How to relate interaction diagrams (hierarchical notation)

28. Invoking static or class methods
public class Foo {
public void doX() {
// Static method call on class Calendar
Locale[] locales = Calendar.getAvailableLocales()
// ... }

29. Polymorphic Messages and Cases

30. Polymorphic Messages and Cases

31. Asynchronous vs. Synchronous Calls
Asynchronous message: Does not wait for a response
“It doesn’t block”
Used in multi-threaded environments
New threads can be created and initiated
Example: In Java
Thread.start
Runnable.run
initiate execution of a new thread

32. Asynchronous vs. Synchronous Calls
Active object: Each instance runs on and controls its own thread of execution
Example: Clock

33. Collaboration Diagram Notation
Link: Connection path between two objects
Indicates a form of navigation or visibility between the objects
Formally: An instance of an association
There can be only one link between two objects
Multiple messages in both directions flow along this link

34. Communication Diagram Notation

35. Messages to “self” or “this”

36. Instance creation in communication diagrams

37. Sequence Numbering
Nested message

38. Sequence Numbering

39. Sequence Numbering

40. Conditional messages

41. Mutually exclusive conditional messages

42. Iteration in communication diagrams

43. Iteration over a collection

44. Static method invocation (message to a class)

45. Modeling polymorphic cases in communication diagrams

46. Asynchronous messages in communication diagrams