重构技巧

重新组织你的函数
在对象之间搬移特性
重新组织数据
简化条件表达式
简化函数调用
处理概括关系

提炼函数1

   1: String name = request.getParameter("Name");
   2: if( name != null && name.length() > 0 ){
   3: ......
   4: }
   5:
   6: String age = request.getParameter("Age");
   7: if( age != null && age.length() > 0 ){
   8: ......
   9: }

转化后：

   1: String name = request.getParameter("Name");
   2: if( !isNullOrEmpty( name ) ){
   3: ......
   4: }
   5: String age = request.getParameter("Age");
   6: if( !isNullOrEmpty( age ) ){
   7: ......
   8: }
   9:
  10:
  11: private boolean isNullOrEmpty( final String string ){
  12: if( string != null && string.length() > 0 ){
  13: return true;
  14: }else{
  15: return false;
  16: }
  17: }

提炼函数２：清除注释

   1: void printOwing() {
   2: //print banner
   3: System.out.println(“*********”);
   4: System.out.println(“Banner”);
   5: System.out.println(“*********”);
   6: //print details
   7: System.out.println ("name: " + _name);
   8: System.out.println ("amount " +
   9: getOutstanding());
  10: }

转化后：

   1: void printOwing(){
   2: printBanner();
   3: printDetails(getOutstanding());
   4: }
   5:
   6: void printBanner(){
   7: System.out.println(“*********”);
   8: System.out.println(“Banner”);
   9: System.out.println(“*********”);
  10: }
  11:
  12: void printDetails (double outstanding){
  13: System.out.println ("name: " + _name);
  14: System.out.println ("amount " + outstanding);
  15: }

将临时变量内联化：

   1: int i = getNo();
   2: if ( i > 100)

转化后：

   1: if ( getNo() > 100)

以查询取代临时变量:

   1: double basePrice = _quantity * _itemPrice;
   2: if (basePrice > 1000)
   3:     return basePrice * 0.95;
   4: else
   5:     return basePrice * 0.98;

转化后：

   1: if (basePrice() > 1000)
   2:     return basePrice() * 0.95;
   3: else
   4:     return basePrice() * 0.98;
   5: ...
   6:
   7: double basePrice() {
   8:     return _quantity * _itemPrice;
   9: }

引入解释性变量：

   1: if ( (platform.toUpperCase().indexOf("MAC") > -1) &&
   2:       (browser.toUpperCase().indexOf("IE") > -1) &&
   3:        wasInitialized() && resize > 0 )
   4:  {
   5:    // do something
   6:  }

转化后：

   1: boolean isMacOs     = platform.toUpperCase().indexOf("MAC") > -1;
   2: boolean isIEBrowser = browser.toUpperCase().indexOf("IE")  > -1;
   3: boolean wasResized  = resize > 0;
   4:
   5: if (isMacOs && isIEBrowser && wasInitialized() && wasResized)
   6: {
   7:     // do something
   8: }

剖解临时变量：

   1: double temp = 2 * (_height + _width);
   2: System.out.println (temp);
   3:
   4: temp = _height * _width;
   5: System.out.println (temp);

转化后：

   1: double perimeter = 2 * (_height + _width);
   2: System.out.println (perimeter);
   3:
   4: double area = _height  * _width;
   5: System.out.println (area);

移除对参数的赋值：

   1: void fun(int a, int b)
   2: {
   3:     if (a > 2)
   4:         a = 3
   5: }

转化后：

   1: void fun(int a, int b)
   2: {
   3:     int tmp = a;
   4:     if ( tmp > 2)
   5:         tmp = 3;
   6:
   7: }

提前退出函数：

   1: double getPayAmount() {
   2:     double result;
   3:     if (_isDead) result = deadAmount();
   4:     else {
   5:         if (_isSeparated) result = separatedAmount();
   6:         else {
   7:             if (_isRetired) result = retiredAmount();
   8:             else result = normalPayAmount();
   9:         };
  10:     }
  11: 　　　　return result;
  12: };

转化后：

   1: double getPayAmount() {
   2:     if (_isDead) return deadAmount();
   3:     if (_isSeparated) return separatedAmount();
   4:     if (_isRetired) return retiredAmount();
   5:     return normalPayAmount();
   6: };

Split Loop：

   1: void printValues() {
   2: double averageAge = 0;
   3: double totalSalary = 0;
   4: for (int i = 0; i < people.length; i++) {
   5: averageAge += people[i].age;
   6: totalSalary += people[i].salary;
   7: }
   8:
   9: averageAge = averageAge / people.length;
  10:
  11: System.out.println(averageAge);
  12: System.out.println(totalSalary);
  13: }

转化后：

   1: void printValues() {
   2: double totalSalary = 0;
   3: for (int i = 0; i < people.length; i++) {
   4:     totalSalary += people[i].salary;
   5: }
   6:
   7: double averageAge = 0;
   8: for (int i = 0; i < people.length; i++) {
   9:     averageAge += people[i].age;
  10: }
  11:
  12: averageAge = averageAge / people.length;
  13:
  14: System.out.println(averageAge);
  15: System.out.println(totalSalary);
  16: }

Split Loop-2

   1: void printValues() {
   2:         System.out.println(averageAge());
   3:         System.out.println(totalSalary());
   4:     }
   5:
   6:     private double averageAge() {
   7:         double result = 0;
   8:         for (int i = 0; i < people.length; i++) {
   9:             result += people[i].age;
  10:         }
  11:         return result / people.length;
  12:     }
  13:
  14:     private double totalSalary() {
  15:         double result = 0;
  16:         for (int i = 0; i < people.length; i++) {
  17:             result += people[i].salary;
  18:         }
  19:         return result;
  20:     }

在对象之间搬移特性：

搬移函数（Move Method)
搬移值域(Move Field)
提炼类(Extract Class)
将类内联化(Inline Class)
隐藏[委托关系](Hide Delegate)
移除中间人(Remove Middle Man)
引入外加函数(Introduce Foreign Method)
引入本地扩展(Introduce Local Extension)

分解表达式:

   1: if(date.before(SUMMER_START) || date.after(SUMMER_END))
   2: charge = quantity * _winterRate + _winterServiceCharge;
   3: else
   4: charge = quantity * _summerRate

转化后：

   1: if(notSummer(date))
   2: charge = winterCharge(quantity);
   3: else
   4: charge = summerCharge(quantity);

Remove Double Negative

if ( !item.isNotFound() )

if ( item.isFound() )