1、控制圈復雜度的9種重構技術-Refactoring: Improving the Design of Existing Code控制圈復雜度：重構可以直接降低圈復雜度的9種重構技術（針對結構化編程）：Composing Methods（重新組織你的函數）Extract Method（提煉函數）Substitute Algorithm（替換你的算法）Simplifying Conditional Expressions（簡化條件表達式）Decompose Conditional（分解條件式）Consolidate Conditional Expression（合并條件式）Consolidate

2、Duplicate Conditional Fragments（合并重復的條件片斷）Remove Control Flag（移除控制標記）Making Method Calls Simpler（簡化函數調用）Separate Query from Modifier（將查詢函數和修改函數分離）Parameterize Method（令函數攜帶參數）Replace Parameter with Explicit Methods（以明確函數取代參數）- Refactoring: Improving the Design of Existing Code針對面向對象編程：Replace Conditi

3、onal with Polymorphism（以多態取代條件式）Extract Method（提煉函數）void printOwing(double previousAmount) Enumeration e = _orders.elements(); double outstanding = previousAmount * 1.2; / print banner System.out.println (*); System.out.println (* Customer Owes *); System.out.println (*); / calculate outstanding whi

4、le (e.hasMoreElements() Order each = (Order) e.nextElement(); outstanding += each.getAmount(); /print details System.out.println (name: + _name); System.out.println (amount + outstanding);void printOwing(double previousAmount) printBanner(); double outstanding = getOutstanding(previousAmount * 1.2);

5、 printDetails(outstanding);void printBanner() / print banner System.out.println (*); System.out.println (* Customer Owes *);double getOutstanding(double initialValue) double result = initialValue; Enumeration e = _orders.elements(); while (e.hasMoreElements() Order each = (Order) e.nextElement(); re

6、sult += each.getAmount(); return result;void printDetails (double outstanding) System.out.println (name: + _name); System.out.println (amount + outstanding);將這段代碼放進一個獨立函數中，并讓函數名稱解釋該函數的用途你有一段代碼可以被組織在一起并獨立出來Substitute Algorithm（替換你的算法）String foundPerson(String people) for (int i = 0; i people.length;

7、i+) if (peoplei.equals (Don) return Don; if (peoplei.equals (John) return John; if (peoplei.equals (Kent) return Kent; return ;String foundPerson(String people) List candidates = Arrays.asList(new StringDon, John,Kent); for (int i=0; ipeople.length; i+) if (candidates.contains(peoplei) return people

8、i; return ;你想要把某個算法替換為另一個更清晰的算法將函數本體替換為另一個算法Decompose Conditional（分解條件式）if (date.before (SUMMER_START) | date.after(SUMMER_END) charge = quantity * _winterRate + _winterServiceCharge;else charge = quantity * _summerRate;if (notSummer(date) charge = winterCharge(quantity);else charge = summerCharge (

9、quantity);你有一個復雜的條件語句從if、then、else三個段落中分別提煉出獨立函數Consolidate Conditional Expression（合并條件式）double disabilityAmount() if (_seniority 12) return 0; if (_isPartTime) return 0; / compute the disability amountdouble disabilityAmount() if (isNotEligableForDisability() return 0; / compute the disability amou

10、nt將這些判斷合并為一個條件式，并將這個條件式提煉成為一個獨立函數你有一系列條件判斷，都得到相同結果Consolidate Duplicate Conditional Fragments（合并重復的條件片斷）if (isSpecialDeal() total = price * 0.95; send(); else total = price * 0.98; send(); if (isSpecialDeal() total = price * 0.95;else total = price * 0.98;send();在條件式的每個分支上有著相同的一段代碼。將這段重復代碼搬移到條件式之外Re

11、move Control Flag（移除控制標記）void checkSecurity(String people) boolean found = false; for (int i = 0; i people.length; i+) if (! found) if (peoplei.equals (Don) sendAlert(); found = true; if (peoplei.equals (John) sendAlert(); found = true; void checkSecurity(String people) for (int i = 0; i 100) result

12、 += (Math.min (lastUsage(),200) - 100) * 0.05; ; if (lastUsage() 200) result += (lastUsage() - 200) * 0.07; ; return new Dollars (result);Dollars baseCharge() double result = usageInRange(0, 100) * 0.03; result += usageInRange (100,200) * 0.05; result += usageInRange (200, Integer.MAX_VALUE) * 0.07;

13、 return new Dollars (result);int usageInRange(int start, int end) if (lastUsage() start) return Math.min(lastUsage(),end) -start; else return 0;若干函數做了類似的工作，但在函數本體中卻包含了不同的值建立單一函數，以參數表達那些不同的值Replace Parameter with Explicit Methods（以明確函數取代參數）void setValue (String name, int value) if (name.equals(height

14、) _height = value; if (name.equals(width) _width = value; Assert.shouldNeverReachHere();void setHeight(int arg) _height = arg;void setWidth (int arg) _width = arg;函數實現完全取決于參數值而采取不同反應針對該參數的每一個可能值，建立一個獨立函數Replace Conditional with Polymorphism（以多態取代條件式）double getSpeed() switch (_type) case EUROPEAN: return getBaseSpeed(); case AFRICAN: return getBaseSpeed() - getLoadF