Index of code metrics

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).