Pattern: NPath complexity is too high
Issue: -
The NPATH metric computes the number of possible execution paths through a function(method). It takes into account the nesting of conditional statements and multi-part boolean expressions (A && B, C || D, E ? F :G and their combinations).
Metric was described at "NPATH: a measure of execution pathcomplexity and its applications". If you need detailed description of algorithm, please read that article, it is well written and have number of examples and details.
Here is some quotes:
An NPATH threshold value of 200 has been established for a function. The value 200 is based on studies done at AT&T Bell Laboratories [1988 year].
Some of the most effective methods of reducing the NPATH value include
- distributing functionality,
- implementing multiple if statements as a switch statement
- creating a separate function for logical expressions with a high count of and (&&) and or (||) operators.
Although strategies to reduce the NPATH complexity of functions are important, care must be taken not to distort the logical clarity of the software by applying a strategy to reduce the complexity of functions. That is, there is a point of diminishing return beyond which a further attempt at reduction of complexity distorts the logical clarity of the system structure.
Rationale: Nejmeh says that his group had an informal NPATH limit of 200 on individual routines; functions(methods) that exceeded this value were candidates for further decomposition - or at least a closer look. Please do not be fanatic with limit 200 - choose number that suites your project style. Limit 200 is empirical number base on some sources of at AT&T Bell Laboratories of 1988 year.
To configure the check:
<module name="NPathComplexity"/>To configure the check with a threshold of 1000:
<module name="NPathComplexity">
<property name="max" value="1000"/>
</module>