CSC310 Lecture 09

Strategy, Decorator, Observer
(20260925)

Transcript

1. CSC 3100 Software Engineering Lecture. Design Patterns Dr. Javier Gonzalez-Sanchez javiergs@calpoly.edu www.javiergs.info ffi o ce: 14 -227
2. Agenda • This is Week 06 • Week 08 - Mond y October 12 - Midterm Review • Wednesd y October 14 - Midterm Ex m a a a 2
3. GoF Patterns 3
4. Patterns in our Sprint 2 libraries 4 Builder XChart How do I construct a complex object clearly? Factory JFreeChart / Jzy3D Centralize object creation Strategy Tribuo Swap the algorithm Decorator Swing, Files, etc Wrap and augment behavior
5. Strategy
6. Strategy Same responsibility. Different algorithm. Common abstraction. 6
7. model = new model (trainer, dataset)
8. Decorator Composite
9. Example • InputStre m input = new FileInputStre m("d t .txt"); • → re ds from ile • Bu eredInputStre m inputBu ered = new Bu eredInputStre m(input); • → dds bu ering • D t InputStre m inputBu eredD t = new D t InputStre m(inputBu ered ); • → dds re dInt(), re dDouble(), re dBoole n(), etc. ff a a a a a a ff a a a a a ff ff a f a a a ff a a a a a a ff a 9
10. • JButton button - new JButton("Click me") • JTextField inputText - new JTextField("Write here") • p nel. dd( notherP nel); • p nel. dd(button); • notherP nel. dd(inputText); a a a a a a a a a a a a a a 10 a a • JP nel p nel = new JP nel(); • JP nel notherP nel = new JP nel();
11. Decorator | Composite 11
12. Decorator | Composite 12
13. Decorator | Composite 13
14. Problem 14
15. Inheritance Approach 15
16. Inheritance Approach 16
17. Inheritance Approach 17
18. • Both llow you to ch nge how n object beh ves. • The decor tor p ttern llows you to extend (decor te) the function lity of n object t runtime. a a a a a a a a a a a a a 18 a • Inherit nce dds beh vior t compil tion time. a a Decorator vs Inheritance
19. Decorator | Composite 19
20. Decorator 20
21. Composite 21
22. To be continued...
23. Example 23
24. Component abstract class Component { public abstract void operation(); } 24 https://github.com/CSC3100/Patterns
25. ConcreteComponent | Ball 25 https://github.com/CSC3100/Patterns
26. Decorator abstract class Decorator extends Component { protected Component component; public void setComponent(Component component) { this.component = component; } @override public void operation() { if (component != null) { component.operation(); } } } 26 https://github.com/CSC3100/Patterns
27. ConcreteDecoratorOne | Bag 27 https://github.com/CSC3100/Patterns
28. ConcreteDecoratorTwo | Box 28 https://github.com/CSC3100/Patterns
29. Main dr w dr w dr w a a a 29 https://github.com/CSC3100/Patterns
30. Composite | Example dr w a 30
31. • Both llow you to ch nge how n object beh ves. • The decor tor p ttern llows you to extend (decor te) the function lity of n object t runtime. a a a a a a a a a a a a a 31 a • Inherit nce dds beh vior t compil tion time. a a Decorator vs Inheritance
32. Observer
33. Observer 33
34. Classroom | Initial Version https://github.com/CSC3100/Patterns 34
35. Student | Initial Version https://github.com/CSC3100/Patterns 35
36. Teacher | Initial Version https://github.com/CSC3100/Patterns 36
37. Observer 37
38. Observer https://github.com/CSC3100/Patterns 38
39. Observable https://github.com/CSC3100/Patterns 39
40. Classroom | New Version https://github.com/CSC3100/Patterns 40
41. Student | New Version https://github.com/CSC3100/Patterns 41
42. Teacher | New Version https://github.com/CSC3100/Patterns 42
43. Important Do not reinvent the wheel! (Do not make another implementation for classes Observer or Observable -they already exist in libraries!) 43
44. Important Depreciated java.util.Observer java.util.Observable The implementation of these packages That is NOT about the Observer pattern being depreciated. 44
45. Important Use java.beans.PropertyChangeListener java.beans.PropertyChangeSupport 45
46. Classroom | Listener Version https://github.com/CSC3100/Patterns 46
47. Student | Listener Version https://github.com/CSC3100/Patterns 47
48. Teacher | Listener Version https://github.com/CSC3100/Patterns 48
49. Thoughts? 49
50. Singleton
51. Singleton 51
52. Singleton class Singleton{ private static Singleton _instance; // Constructor is 'protected' protected Singleton() {} public static Singleton getInstance(){ if (_instance == null){ _instance = new Singleton(); } return _instance; } } https://github.com/CSC3100/Patterns 52
53. Singleton https://github.com/CSC3100/Patterns 53
54. Warning Do not Abuse of the Singleton You are transforming OOP into Structural Programming!! 🙈 54
55. Homework Reading https://medium.com/javarevisited/design-patterns-101-hello-singleton-2d3f227c7729 55
56. CSC 3100 Software Engineering Javier Gonzalez-Sanchez, Ph.D. javiergs@calpoly.edu Fall 2026 Copyright. These slides may be used only as study material for CSC 5100 within the California State University system. They may not be distributed or used for any other purpose.