Index of code metrics

Cognitive Complexity (COGNITIVE)

Operation metric. Can be calculated on any non-abstract operation.

Class metric. Can be computed on classes and enums - it’s just the sum of all method’s cogntive complexities.

Description

See the corresponding Java metric Cognitive Complexity for a general description.

The rule CognitiveComplexity by default reports methods with a complexity of 15 or more and classes the have a total complexity (sum of all methods) of 50 or more. These reported methods should be broken down into less complex components.

Cyclomatic Complexity (CYCLO)

Operation metric. Can be calculated on any non-abstract operation.

Description

Number of independent paths through a block of code [Lanza05]. Formally, given that the control flow graph of the block has n vertices, e edges and p connected components, the cyclomatic complexity of the block is given by CYCLO = e - n + 2p [McCabe76]. In practice it can be calculated by counting control flow statements following the standard rules given below.

The standard version of the metric complies with McCabe’s original definition:

• Methods have a base complexity of 1.
• +1 for every control flow statement (if, catch, throw, do, while, for, break, continue) and conditional expression (?:).
• else, finally and default don’t count;
• +1 for every boolean operator (&&, ||) in the guard condition of a control flow statement.

Code examples

class Foo {
  void baseCyclo() {                // Cyclo = 1
    highCyclo();
  }
  
  void highCyclo() {                // Cyclo = 10
    int x = 0, y = 2;
    boolean a = false, b = true;
    
    if (a && (y == 1 ? b : true)) { // +3
      if (y == x) {                 // +1
        while (true) {              // +1
          if (x++ < 20) {           // +1
            break;                  // +1
          }
        }
      } else if (y == t && !d) {    // +2
        x = a ? y : x;              // +1
      } else {
        x = 2;
      }
    }  
  }     
}

Weighted Method Count (WMC)

Class metric. Can be computed on classes and enums.

References

Lanza05: Lanza, Marinescu; Object-Oriented Metrics in Practice, 2005.

McCabe76: McCabe, A Complexity Measure, in Proceedings of the 2nd ICSE (1976).