The document discusses advanced design patterns, particularly focusing on the singleton pattern, its various implementations, and associated issues such as memory leaks and serialization problems. It also outlines the design of a system that includes data structures for an in-memory file system and a parking lot using object-oriented principles. Key solutions and examples are provided for issues with singleton implementation, reflection, serialization, and cloneable.

1. DESIGN
PATTERN
ADVANCED I
CLOVERLAB. INC
JIEYI WU
2018/10/31

2. OUTLINE
• ISSUES OF SINGLETON PATTERN
• PRACTICING DESIGN A SYSTEM

3. 3
Issues of
Single Pattern
For what there’re so many
ways to implement?
• Normal Singleton
• Thread-safe Singleton (Synchroized)
• Thread-safe Singleton (Double Click Lock)
• Private inner static Singleton
• Initialized First Singleton
• Enum Singleton

4. Memory
Memory
Leak
Resource
Costing
Reflection Serialization Cloneable
Real issues for Singleton
That’s why there’re so many ways
4

5. Issue of Reflection
5
Output:-
instance1.hashCode():- 366712642
instance2.hashCode():- 1829164700

6. 6
Solution for
Reflection
As enums don’t have any constructor so it is
not possible for Reflection to utilize it.

7. Issue of Serialization
7
Output:-
instance1.hashCode():- 1550089733
instance2.hashCode():- 865113938

8. 8
Solution for
Serialization

9. Issue of Cloneable
9
Output:-
instance1.hashCode():- 366712642
instance2.hashCode():- 1829164700

10. 10
Overcome for
Cloneable

11. PRACTICING
DESIGN A SYSTEM!
LET’S DIRTY OUR HAND!
11

12. Design data structures and algorithms for in-memory file system
12
• Composite Pattern
• Folder
• Files
• Name
• Created Date
• Create
• Write
• Modify
• Delete

13. Abstract Class
13
• All Common Properties
• Name
• Created Date

14. Concrete Class
14
• Keep all Files & Directories

15. § Three type of Cars( ! , " , #)
§ Spaces
Bus needs 3 spaces
Car needs 1 space
Auto-bike needs 1 space
Design a parking lot
Using object-oriented principles
15

16. 16
Q & A

17. THANK YOU
17
Jieyi Wu