Reduce cycle complexity

Reduce cycle complexity

demand ：

Code optimization ： Recently, the company required to rectify the code , The cyclomatic complexity is involved . I have been exposed to time complexity before , So I have to search a wave of information .

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sketch ：

1. Concept ：

​ Cyclomatic complexity （Cyclomatic complexity,CC） Also known as conditional complexity , It's a measure of code complexity , Its symbol is V(G). In short , That is, count the number of conditional judgments in the code .

2. Influencing factors ：

• if sentence
• while sentence
• for sentence
• case sentence
• catch sentence
• and and or Boolean operation
• ? : Ternary operator

3. Calculation method ：

**V (G） ** =P +1

P Represents the number of conditional judgments in the code , That is, the number of influencing factors above ,1 Cycle complexity representing normal order

example ：

The complexity of the next cycle is 2：

while ("0".equals(a)){
    
           if (b != null){
    
               c++;
           }
        }

4. Be careful :

1. if (a == null && b != null) The cycle complexity is 2, Because there are two judgments , So when you plan to put two if When combining conditions , The cycle complexity has not changed , What changes is cognitive complexity .
2. if-else and if The cyclomatic complexity is 1, Don't think about leaving only if Get rid of else, The results have not changed
   3. Conditional nesting and presentation do not affect the calculation of cycle complexity , For example, put if Inside for Cycle to the outside , As a result, the cyclomatic complexity is still 2
   4. if Conversion to ternary operators does not affect cyclomatic complexity
   5. The purpose of reducing cycle complexity is to optimize code , Reduce maintenance costs , Don't force code extraction to complicate in order to reduce
   6. Never change the original logic

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An optimization method ：

At present, only a few methods are used , Here are some optimization examples

• Try to use encapsulated util class

  // If the string is empty 
  // Before the change ：
  if (a == null || a.length() == 0){
        
      b ++;
  }
  // After reform ：
  if (StringUtil.isEmpty()){
        
      b ++;
  }
  

  // Set empty judgment （List\Map\Set）
  // Before the change ：
  if (list == null || list.size() == 0){
        
      b ++;
  }
  // After reform ：
  if (CollectionUtils.isEmpty){
        
      b ++;
  }
  

  // Close various streams 
  // Before the change ：
  if (stream != null){
        
      try {
        
          stream.close();
      } catch (IOException e) {
        
          e.printStackTrace();
      }
  }
  // After reform ：
  IOUtils.closeQuietly(stream)
  

• switch/case Turn into map

  // Before the change ：
  switch (a){
        
      case 1:
          b = "f";
          break;
      case 2:
          b = "g";
          break;
      default:
          break;
  }
  // After reform ：
  Map<Integer,String> map = new HashMap<>();
          map.put(1,"f");
          map.put(2,"g");
          b = map.get(a);
  

• Extract Method

  // Before the change ：
  if ( b == null ){
        
      a = 1;
  }else{
        
      a= 4;
  }
  // After reform ：
  public static <T> T getValueByCondition(boolean condition,T valueOfTrue,T valueOfFalse){
        
          if (condition){
        
              return valueOfTrue;
          }else {
        
              return valueOfFalse
          }
      }
  
  a = getValueByCondition(b == null,1,4);