refactoring tutorial

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3. 3 Confidential 12/13/2011

4. : ? Bad Code Good Code

5. :: Bad Code Broken Window Theory

6. , . Tool Refactoring public int getCharge(int quantity) { public int getCharge(int quantity) { int charge = 0; int charge = 0; Date now = new Date(); Date now = new Date(); // Summer if (isSummerTime(now)) { if (now.before(SUMMER_START)|| now.after(SUMMER_END)) { charge = quantity * WINTER_RATE + charge = quantity * WINTER_RATE + WINTER_SERVICEC_CHARGE; WINTER_SERVICEC_CHARGE; } else { } else { charge = quantity * SUMMER_RATE; charge = quantity * SUMMER_RATE; } } return charge; return charge } } private boolean isSummerTime(Date now) { return now.before(SUMMER_START) || now.after(SUMMER_END); }

7. : ? ? ?

8. : ? , , . ,

9. : (10~30), .

10. : Publish Ex) Android Service.onStart() I/F Delegation : API Publish Throw Delegation : Super Exception , ?

11. : , . With design I can think very fast, but my thinking is full of little holes Alistair Cockburn Role , . . . Complexity

12. : . . , .

13. () Switch

14. : Obvious Copy & Paste Unobvious (ex, , ) ExtractMethod ExtractMethod -> Pull Up Field or Pull Up Method -> Form Template Method

15. : . People often make assumptions based on the object names alone Word Cunningham Rename Method Rename Field Rename Constants Tip ! add, register, put, create -> add

16. : PriceCalculator Product .. calculate() .. getQuantity() bmethod() getDiscountRate() Move Method

17. : Class A Class B (private .. .. ) amethod() xmethod() bmethod() ymethod() Move Method Change Bidirectional Reference to Unidirectional Extract Hierarchy-> Hide Delegate

18. : Extract Method Rename Method Introduce Assertion

19. : . Extract Method .

20. : . Replace Parameter with Method Object Preserve Whole Object Introduce Parameter Object Caller Callee

21. : Switch Switch , Switch OOP Switch Switch Step 1: Extract Method Step 2: Move Method Step 3: Replace Type Code with Subclass or Replace Type Code with State/Strategy Switch 21 Confidential 12/13/2011

22. . , . . 22 Confidential 12/13/2011

25. : .

26. : -> - -> Extract Method -> Rename Method -> Introduce Assertion

27. : - package ch3;public class Matcher { public Matcher() { } [Rename Method] // . public boolean compare(int[] expected, int[] actual, int clipLimit, int delta) { // clipLimit . [Extract Method] for (int i = 0; i < actual.length; i++) if (actual[i] > clipLimit) actual[i] = clipLimit; // . [Extract Method] if (actual.length != expected.length) return false; // delta . for (int i = 0; i < actual.length; i++) if (Math.abs(expected[i] - actual[i]) > delta) return false; return true; }} 27 Confidential 12/13/2011

28. Refactoring : Extract Method .{ { // clipLimit . // clipLimit . for (int i = 0; i < actual.length; i++) for (int i = 0; i < actual.length; i++) if (actual[i] > clipLimit) if (actual[i] > clipLimit) actual[i] = clipLimit; actual[i] = clipLimit; }} private void cutLargeValues(int[] values, int limit) { for (int i = 0; i < values.length; i++) if (valuesl[i] > limit) values [i] = limit; } 28 Confidential 12/13/2011

29. Refactoring : Rename Method . !! 29 Confidential 12/13/2011

30. Refactoring : Introduce Assertion assertion double getExpenseLimit() { double getExpenseLimit() { // should have either expense limit or a primary project return Assert.isTrue (_expenseLimit != NULL_EXPENSE || _primaryProject != null); (_expenseLimit != NULL_EXPENSE) ? return (_expenseLimit != NULL_EXPENSE) ? _expenseLimit: _expenseLimit: _primaryProject.getMemberExpenseLimit(); _primaryProject.getMemberExpenseLimit();} } Assertion . Assertion Assertion . Assertion Assertion Extract Method 30 Confidential 12/13/2011

31. : - . , -> , , ? -> ExtractMethod

32. : -> Extract Class -> Extract Subclass -> Extract Interface

33. Refactoring : Extract Class , , ! 33 Confidential 12/13/2011

34. Refactoring : Extract Class 34 Confidential 12/13/2011

35. Refactoring : Extract Subclass JobItem +getTotalPrice() JobItem +getUnitPrice() +getTotalPrice() +getUnitPrice() +getEmployee() LaborItem +getUnitPrice() +getEmployee() Extract Class Extract Subclass Extract Subclass (variation) . . Extract Class (variation) . , . 35 Confidential 12/13/2011

36. Refactoring : Extract Interface , Billable +getRate() Employee +hasSpecialSkill() +getRate() +hasSpecialSkill() +getName() Employee +getDepartment() +getRate() +hasSpecialSkill() +getName() +getDepartment() Extract Superclass Extract Interface . 36 Confidential 12/13/2011

37. : - Coupling . -> Replace Parameter with Method -> Preserve Whole Object -> Introduce Parameter Object Coupling

38. Refactoring : Replace Parameter with Method , . , Int basePrice = quantity * itemPrice; int basePrice = quantity * itemPrice;discountLevel = getDiscountLevel(); double finalPrice = getDiscountedPrice(basePrice);double finalPrice = getDiscountedPrice(basePrice, discountLevel);

39. Refactoring : Preserve Whole Object Int low = daysTempRange().getLow();Int high = daysTempRange().getHigh(); withinPlan = plan.withinRange(daysTempRange());withinPlan = plain.withinRange(low, high) , ,

40. Refactoring : Introduce Parameter Object -> -> ,

42. : . : , : , , (Type Embedded in Name) (Uncommunicative Name) (Inconsistent Name)

43. : ex) addCourse(Course c) ex) iCount -> , -> -> Rename Method, Rename Field, Rename Constant , .

44. : Rename Method, Rename Field, Rename Constant * , .

45. : . Ex) add(), store(), put(), place(), register() . -> Rename Method, Rename Field, Rename Constant , .

48. : & , , , , , , . . . . -> Collapse Hierarchy -> Inline Class -> Inline Method -> -> Remove Parameter , , , .48 Confidential 12/13/2011

49. Refactoring : Inline Class & Collapse Hierarchy* Inline Class .* Collapse Hierarchy LoginContext LoginModule +authenticate() Collapse Hierarchy IDPasswordLoginModule KerberosLoginModule x x FingerPrintLoginModule +authenticate() +authenticate() +authenticate() 49 Confidential 12/13/2011

50. Refactoring : Inline Method .int getRating() { int getRating() { return (moreThanFiveLateDeliveries()) ? 2 : 1; return (_numberOfLateDeliveries > 5) ? 2 : 1;} }boolean moreThanFiveLateDeliveries() { return _numberOfLateDeliveries > 5;} Indirection Refactoring Refactoring 50 Confidential 12/13/2011

52. : . . . . (Magic Number) (Duplicated Code) (Alternative Classes with Different Interfaces)

53. : . Replace Magic Number with Symbolic Constant ,

54. : public void analyze(File file) throws FileNotFoundException { private static final int INDEX_TYPE = 0; BufferedReader reader = new BufferedReader(new FileReader(file)); private static final int INDEX_TIME = 1; private static final int INDEX_URL = 2; try { private static final int INDEX_IPADRESS = 3; String aLine = reader.readLine(); public void analyze(File file) throws FileNotFoundException { while (aLine != null) { BufferedReader reader = new BufferedReader(new FileReader(file)); // type, time, id, ip address String[] record = aLine.split(SEPERATOR); try { String aLine = reader.readLine(); AccessLog aLog = new AccessLog(); aLog.setType(record[0]); while (aLine != null) { aLog.setTime(record[1]); // type, time, id, ip address aLog.setUrl(record[2]); String[] record = aLine.split(SEPERATOR); aLog.setIpAddress(record[3]); Replace Magic Number with Symbolic Constant AccessLog aLog = new AccessLog(); aLine = reader.readLine(); aLog.setType(record[INDEX_TYPE]); } aLog.setTime(record[INDEX_TIME]); } catch (IOException e) { aLog.setUrl(record[INDEX_URL]); e.printStackTrace(); aLog.setIpAddress(record[INDEX_IPADRESS]); } finally { // .. aLine = reader.readLine(); } }} } catch (IOException e) { e.printStackTrace(); } finally { // .. } } , 54 Confidential 12/13/2011

55. : . . Copy & Paste -> Extract Method -> Extract Method -> Pull Up Field or Pull Up Method -> Form Template Method -> Extract Class , -> Substitute Algorithm .

56. : 56 Confidential 12/13/2011

57. : , -> Rename Method -> Move Method, Add Parameter, Parameterize Method -> Extract Superclass -> .

59. : ? Boolean (Complicated Boolean Expression) (Simulated Inheritance) 59 Confidential 12/13/2011

60. : Boolean , , ) public boolean isAcceptable1(int score, int income, boolean authorized) { if (!((score > 700) || ((income >= 40000) && (income 500)) || (income > 100000)) ) return false; else return true; } DeMorgans Law)public boolean isAcceptable2(int score, int income, boolean authorized) { if (((score 100000) || !authorized || (score = 40000) && (income 500)) || (income > 100000)) ) return false; else return true; } Introduce Explaining Variable) public boolean isAcceptable3(int score, int income, boolean authorized) { boolean hasMidRangeIncome = (income >= 40000) && (income 100000;; boolean hasHighScore = score > 700; if (!( hasHighScore || (hasMidRangeIncome && authorized && (score > 500)) || hasHighIncome) ) return false; else return true; } 61 Confidential 12/13/2011

62. Refactoring : Introduce Explaining Variable & DeMorgans LawIntroduce Explaining Variable) public boolean isAcceptable3(int score, int income, boolean authorized) { boolean hasMidRangeIncome = (income >= 40000) && (income 100000;; boolean hasHighScore = score > 700; if (!( hasHighScore || (hasMidRangeIncome && authorized && (score > 500)) || hasHighIncome) ) return false; else return true; } Introduce Explaining Variable) & DeMorgans Law public boolean isAcceptable4(int score, int income, boolean authorized) { boolean hasMidRangeIncome = (income >= 40000) && (income 100000;; boolean hasHighScore = score > 700; if (!hasHighScore && (!hasMidRangeIncome || !authorized || !(score > 500)) && !hasHighIncome) return false; else return true; } 62 Confidential 12/13/2011

63. Refactoring : Decompose Conditional) public boolean isAcceptable1(int score, int income, boolean authorized) { if (!((score > 700) || ((income >= 40000) && (income 500)) || (income > 100000)) ) return false; else return true; } Decompose Conditional) public boolean isAcceptable5(int score, int income, boolean authorized) { if (!(isHighScore(score) || ( isMidRangeIncome(income) && authorized && isMidScore(score)) || isHighIncome(income)) ) return false; else return true; } 63 Confidential 12/13/2011

64. Refactoring : Decompose Conditional) public boolean isAcceptable5(int score, int income, boolean authorized) { if (!(isHighScore(score) || ( isMidRangeIncome(income) && authorized && isMidScore(score)) || isHighIncome(income)) ) return false; else return true; } ) public boolean isAcceptable6(int score, int income, boolean authorized) { if (isHighScore(score) || ( isMidRangeIncome(income) && authorized && isMidScore(score)) || isHighIncome(income) ) return true; else return false; } 64 Confidential 12/13/2011

65. Refactoring : Consolidate Conditional Expression ) public boolean isAcceptable1(int score, int income, boolean authorized) { if (!((score > 700) public|| ((income >= 40000) && (income 500)) { || (income > 100000)) ) ifreturn false; (isHighScore(score) else|| ( isMidRangeIncome(income) && authorized && isMidScore(score)) || isHighIncome(income) return true; } ) return true; else return false; } Consolidate Conditional ExpressionConsolidate Conditional Expression) public boolean isAcceptable8(int score, int income, boolean authorized) { if (isHighScore(score) || isHighIncome(income)) // return true; if (isMidRangeIncome(income) && authorized && isMidScore(score)) return true; else Refactoring return false; } - - - 65 Confidential 12/13/2011

66. Boolean 66 Confidential 12/13/2011

67. : public class Employee { private int type; private static final int ENGINEER = 0; 1 private static final int SALESMAN = 1; private static final int MANAGER = 2; public Employee(int type) { this.type = type; Type } Replace Type Code with public int calculatePayment() { switch (type) { case ENGINEER: return monthlySalary; State/Strategy case SALESMAN: return monthlySalary + commission; case MANAGER: return monthlySalary + bonus; Replace Type Code with default: throw new RuntimeException("Incorrect Employee"); Subclass }} public String getJobTitle() { 2 switch (type) { case ENGINEER: Replace Conditional with return "Engineer"; case SALESMAN: Class return "Salesman"; case MANAGER: return "Manager"; default: throw new RuntimeException("Incorrect Employee"); } }} 67 Confidential 12/13/2011

68. Boolean 68 Confidential 12/13/2011

71. : Book Book height title genre category width author weight price getDiscount() getRequiredDeliveryRoom() content Book , , 71 Confidential 12/13/2011

72. : ->Replace Data Value with Object -> : Replace Type Code with Class : Replace Array with Object 72 Confidential 12/13/2011

73. Refactoring : Replace Data with Object User +firstName: String +lastName: String Order Customer Replace Data with+orderNumber: String Object Order +firstName: String+customeFirstNamer: String 1 1 +lastName: String+customerLastName: String +orderNumber+price: float+addressState: String Address+addressCity: String +state+addressStreet: String +city+addressZipCode1: String +zipCode1+addressZipCode 2: String 1 1 +zipCode2+telAreaCode: String+telNumber: String +getDeliveryCost() home Contact office +areaCode +number 73 Confidential 12/13/2011

74. Refactoring : Replace Array with Object String[] row = new String[3]; Performance row = new Performance(); row [0] = "Liverpool"; row.setName("Liverpool"); row [1] = "15"; row.setWins("15"); 74 Confidential 12/13/2011

75. : public field getter/setter 1- : Encapsulate Field 2- : Remove Setting Method 3-Collection : Encapsulate Collection 4- : Extract Method and Move Method 5- , , public , getter/setter 75 Confidential 12/13/2011

76. Refactoring : Encapsulate Collection Collection get/set (read-only view) , add/remove Collection (get) Collection . Collection (set) Collection Collection . 76 Confidential 12/13/2011

77. Encapsulate Collection 77 Confidential 12/13/2011

79. : .( ) .( ) . , Is-A , Replace Inheritance with Delegation Extract Subclass, Push Down Field, Push Down Method , . -> Java Collection79 Confidential 12/13/2011

80. : Drawable Drawable +draw() Line +draw() Exception +getArea() +getArea() , 0 Rectangle Circle Rectangle Circle Line +getArea() Drawable +draw() Shape Line +getArea() +getLength() Rectangle Circle80 Confidential 12/13/2011

81. Liskov Substitution Principle(LSP)Functions that use pointers or references to base classes must be able to use objects of derived classes without knowing it. , Square Rectangle . -> , LSP . Shape Rectangle.setWidth() Square.setWidth() . +getArea() Shape Rectangle Circle +getArea() +width+height+setWidth()+setHeight()+getWidth() Square Rectangle Circle+getHeight() +width +width +height +height +setLength() +setWidth() +setHeight() Square +getWidth() +getHeight()OOD IS-A .81 Confidential 12/13/2011

82. Refactoring : Replace Inheritance with Delegation 82 Confidential 12/13/2011

83. : ( ) (private ) . . -> Self Encapsulate Field -> Form Template Method -> Replace Inheritance with Delegation 83 Confidential 12/13/2011

84. Refactoring : Form Template Method , , , , , .84 Confidential 12/13/2011

85. : , Delegation. . -> Collapse Hierarchy -> Inline Class .85 Confidential 12/13/2011

87. : 87 Confidential 12/13/2011

88. : & Class A Class B Class A Class B .. .. .. attributeA amethod() getX() amethod() bmethod() getY() bmethod() amethod() private . - Move Method Move Method - Extract Hierarchy-> Hide Delegate - Change Bidirectional Reference to Unidirectional88 Confidential 12/13/2011

89. Refactoring : Hide Delegate , (Delegate) . Client Department . Law of Demeter . : . 89 Confidential 12/13/2011

90. Refactoring : Change Bidirectional Association to Unidirectional . Bidirectional Association . -> Zombie Cluster -> Coupling 90 Confidential 12/13/2011

91. : & Remove Middleman Hide Delegate . person.getDepartment().getManager() Delegate Feature . Server . . . Delegate Feature Server . . Hide Delegate Remove Middleman ! , . 91 Confidential 12/13/2011

93. : (Divergent Change) (Parallel Inheritance Hierarchies) (Combinational Explosion) (Shotgun Surgery) 93 Confidential 12/13/2011

94. : (Divergent Change) Shape Shape ShapWriter +draw() +draw() +persist() +persist() 5px .. Binary , XML .. Rectangle Circle Triangle RectangleWriter CircleWriter TriangleWriter Rectangle Circle Triangle +draw() +draw() +draw() +persistence() +persistence() +persistence() +draw() V +draw() V +draw()V +persist() V +persist() V +persist() V . . Extract Class Class . 94 Confidential 12/13/2011

95. : SRP Test Method Uses , Used History ? 95 Confidential 12/13/2011

96. : Shape ShapWriter +draw() +persist() Rectangle Circle Triangle RectangleWriter CircleWriter TriangleWriter +draw() +draw() +draw() +persistence() +persistence() +persistence() -> . Move Method, Move Field 96 Confidential 12/13/2011

97. : ShapeWriter Triangle +persist() ? DB ? Rectangle Circle +draw() +draw() RectangleExcelWriter RectangleXmlWriter RectangleExcelWriter RectangleXmlWriter (or Concern) . Replace Inheritance with Delegation Tease Apart Inheritance 97 Confidential 12/13/2011

98. Refactoring : Tease Apart Inheritance , . , . 98 Confidential 12/13/2011

99. : (Shotgun Surgery) . . . Move Method, Move Field & Persistence 99 Confidential 12/13/2011

100. 100 Confidential 12/13/2011

101. : . Introduce Foreign Method Introduce Local Extension [Introduce Local Extension] 101 Confidential 12/13/2011

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