CSE460 Lecture 17

Software Analysis and Design
Singleton
(202103)

Transcript

1. jgs CSE 460 Software Analysis and Design Lecture 17: Singleton Dr. Javier Gonzalez-Sanchez javiergs@asu.edu javiergs.engineering.asu.edu | javiergs.com PERALTA 230U Office Hours: By appointment
2. jgs Previously …
3. jgs 00010000 Practice
4. jgs 00010000 Observer Pattern
5. jgs 00010000 Decorator Pattern
6. jgs 00010000 Solution: UI + Observer + Decorator
7. jgs Let us Continue the Practice
8. jgs 00010000 GoF Patterns
9. jgs Singleton
10. jgs 00010000 Singleton A B
11. jgs 00010000 Singleton A B Printer DataBaseConnection UniversityPresident Pacman Logger ControlCenter
12. jgs 00010000 Singleton
13. jgs 00010000 Singleton class Main { public static void main(String []a){ // Constructor is protected -- cannot use new Singleton s1 = Singleton.getInstance(); Singleton s2 = Singleton.getInstance(); // Test for same instance if (s1 == s2){ // true - Objects are the same instance } } }
14. jgs 00010000 Singleton class Singleton{ private static Singleton instance; // Constructor is 'protected' protected Singleton() {} public static Singleton getInstance(){ if (instance == null){ instance = new Singleton(); } return instance; } }
15. jgs 00010000 Practice
16. jgs 00010000 A Singleton
17. jgs 00010000 Add More Objects
18. jgs CSE 460 Software Analysis and Design Javier Gonzalez-Sanchez javiergs@asu.edu Fall 2020 Disclaimer. These slides can only be used as study material for the class CSE460 at ASU. They cannot be distributed or used for another purpose.