The document discusses refactoring and improving existing code. It describes how the Eclipse IDE has been refactored and improved over multiple versions from 1.0 to 3.7. It also discusses common code smells like duplicated code, long methods, large classes, and long parameter lists that indicate needs for refactoring. Various refactoring techniques are presented, such as extracting methods, extracting classes, replacing parameters with method calls, and introducing parameter objects. The importance of unit testing during refactoring is also emphasized.

1. Refactoring
Improving The Design of Existing Code
Reporter：Jiayun Zhou <jiayun.zhou@iisigroup.com>
Date ：2011/07/13

2. Outline
Introduction
Bad Smells & Refactorings
Conclusion
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3. Introduction

4. Eclipse 1.0 – Nov 2001
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5. Eclipse 2.0 – Jun 2002
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6. Eclipse 2.1 – Mar 2003
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7. Eclipse 3.7 – Jun 2011
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9. Martin Fowler
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10. Kent Beck
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11. Bad Smells & Refactorings

12. Bad Smell
If it stinks, change it.
-Grandma Beck,
discussing child-rearing philosophy
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13. WTF
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14. What the Fxxk
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16. Good Programmer
• 30% Good Habits
• 30% English
• 40% Passion, Talent, Practice,
and Everything Else
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17. Duplicated Code (Bad Smell)
DRY
(Don't Repeat Yourself)
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18. Duplicated Code (Bad Smell)
DRY
(Don't Repeat Yourself)
vs.
WET
(We Enjoy Typing)
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19. Pull Up Method
(Refactoring)
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20. Pull Up – 1 (Eclipse)
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21. Pull Up – 2 (Eclipse)
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22. Pull Up – 3 (Eclipse)
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23. Pull Up – 4 (Eclipse)
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24. Pull Up – 5 (Eclipse)
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25. Long Method (Bad Smell)
• Short methods are good
• Whenever we feel the need to
comment something, we write
a method instead
• Method name explains the
intention
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26. Extract Method
(Refactoring)
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27. Extract Method – 1 (Eclipse)
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28. Extract Method – 2 (Eclipse)
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29. Extract Method – 3 (Eclipse)
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30. Conditionals and loops also give
signs for extractions.
Use Decompose Conditional to deal
with conditional expressions.
With loops, extract the loop and the
code within the loop into its own
method.
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31. Large Class (Bad Smell)
• Trying to do too much
• Shows up as too many instance
variables
• Duplicated code cannot be far
behind
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32. Extract Class
(Refactoring)
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33. Extract Class – 1 (Eclipse)
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34. Extract Class – 2 (Eclipse)
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35. Extract Class – 3 (Eclipse)
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36. Long Parameter List
(Bad Smell)
• Hard to understand
• Become inconsistent and
difficult to use
• Forever changing them as you
need more data
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37. Replace Parameter with Method
(Refactoring)
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38. Preserve Whole Object
(Refactoring)
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39. Introduce Parameter Object
(Refactoring)
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40. Introduce Parameter Object –
01 (Eclipse)
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41. Introduce Parameter Object –
02 (Eclipse)
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42. Introduce Parameter Object –
03 (Eclipse)
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43. Comments (Bad Smell)
• They are sweet smell
• Don't use as a deodorant
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44. Conclusion

45. How to refactor safely?
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46. Unit Test
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48. Ｈow about the translation?
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49. 中譯
你可以選擇每個 class 和函式的名字，
這給了你一個解釋自己意圖的機會。
class 或函式內部則解釋實現這個意圖
的作法。如果class 和函式內部又以「
更小單元的意圖」來編寫，你所寫的
程式碼就可以「與其結構中的大部分
重要資訊溝通」。 (p.61)
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50. 原文
Choosing the name of each class and the name
of each method gives you an opportunity to
explain what you intend. The internals of the
class or method explain how the intention is
realized. If the internals also are written in
terms of intention in yet smaller pieces, you
can write code that communicates most of
the important information about its own
structure.
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51. Copyright by IISI. All rights reserved 51

52. 我的翻譯
你可以選擇每個 class 和函式的名字，
這給了你一個解釋自己意圖的機會。
class 或函式內部則解釋實現這個意圖
的作法。如果class 和函式內部又以「
更小單元的意圖」來編寫，你所寫的
程式碼就可以「表達出它自己結構的
大部分重要資訊」。
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53. 盡信書不如無書
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55. 琴鍵有限，琴藝無限
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56. - Thank You -
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