How to improve Cyclomatic Complexity?

Question

Cyclomatic Complexity will be high for methods with a high number of decision statements including if/while/for statements. So how do we improve on it?

I am handling a big project where I am supposed to reduced the CC for methods that have CC > 10. And there are many methods with this problem. Below I will list down some eg of code patterns (not the actual code) with the problems I have encountered. Is it possible that they can be simplified?

Example of cases resulting in many decision statements:

Case 1)

if(objectA != null) //objectA is a pass in as a parameter
{
 objectB = doThisMethod();
 if(objectB != null)
 {
  objectC = doThatMethod();
  if(objectC != null)
  {
   doXXX();
  }
  else{
   doYYY();
  }
 }
 else
 {
  doZZZ();
 }
}

Case 2)

if(a < min)
 min = a;

if(a < max)
 max = a;

if(b > 0)
 doXXX();

if(c > 0)
{
 doYYY();
}
else
{
 doZZZ();
 if(c > d)
  isTrue = false;

 for(int i=0; i<d; i++)
  s[i] = i*d;

 if(isTrue)
 {
  if(e > 1)
  {
   doALotOfStuff();
  }
 }
}

Case 3)

// note that these String Constants are used elsewhere as diff combination,
// so you can't combine them as one
if(e.PropertyName.Equals(StringConstants.AAA) ||
e.PropertyName.Equals(StringConstants.BBB) ||
e.PropertyName.Equals(StringConstants.CCC) ||
e.PropertyName.Equals(StringConstants.DDD) ||
e.PropertyName.Equals(StringConstants.EEE) ||
e.PropertyName.Equals(StringConstants.FFF) ||
e.PropertyName.Equals(StringConstants.GGG) ||
e.PropertyName.Equals(StringConstants.HHH) ||
e.PropertyName.Equals(StringConstants.III) ||
e.PropertyName.Equals(StringConstants.JJJ) ||
e.PropertyName.Equals(StringConstants.KKK)) 
{
 doStuff();
}

Answer 1

Case 1 - deal with this simply by refactoring into smaller functions. E.g. the following snippet could be a function:

objectC = doThatMethod();
if(objectC != null)
{
 doXXX();
}
else{
 doYYY();
}

Case 2 - exactly the same approach. Take the contents of the else clause out into a smaller helper function

Case 3 - make a list of the strings you want to check against, and make a small helper function that compares a string against many options (could be simplified further with linq)

var stringConstants = new string[] { StringConstants.AAA, StringConstants.BBB etc };
if(stringConstants.Any((s) => e.PropertyName.Equals(s))
{
    ...
}