CCyclomaticComplexity.qhelp

<!DOCTYPE qhelp PUBLIC
  "-//Semmle//qhelp//EN"
  "qhelp.dtd">
<qhelp>
<overview>
<p>
The cyclomatic complexity of a method (or constructor) is the number
of possible linearly-independent execution paths through that method (see [Wikipedia]).
It was originally introduced as a complexity measure by Thomas McCabe
[McCabe].
</p>

<p>A method with high cyclomatic complexity is typically difficult to
understand and test.
</p>

</overview>
<example>

<sample src="CCyclomaticComplexity.java" />

<p>
The control flow graph for this method is as follows:
</p>

<img src="./CCyclomaticComplexity_ControlFlow.png" alt="Control Flow Diagram" />

<p>
As you can see from the graph, the number of linearly-independent execution
paths through the method is 3. Therefore, the cyclomatic complexity is 3.</p>

</example>
<recommendation>

<p>
Simplify methods that have a high cyclomatic complexity. For example,
tidy up complex logic, and/or split methods into multiple smaller
methods using the 'Extract Method' refactoring from [Fowler].
</p>



</recommendation>
<references>


<li>
M. Fowler, <em>Refactoring</em>. Addison-Wesley, 1999.
</li>
<li>
T. J. McCabe, <em>A Complexity Measure</em>. IEEE Transactions on Software Engineering, SE-2(4), December 1976.
</li>
<li>
Wikipedia: <a href="http://en.wikipedia.org/wiki/Cyclomatic_complexity">Cyclomatic complexity</a>.
</li>


</references>
</qhelp>