Dead Code Detection

Research [Strei2014] and other sources (e.g. [Pizz2013]) have shown that typical software code bases contain 5-10% “dead code”, i.e. code that can be removed without reducing the functionality.
Streamlining the code base by identifying and removing dead code has several benefits:

  • Less maintenance cost: Whilst dead code is less likely to be changed frequently, it still has to be understood and might be effected by refactorings.
  • Smaller footprint: Less code makes the development environment faster, the build and deployment processes are more efficient, and the size of runtime artifacts are smaller.
  • Better precision for calculated metrics: Dead code contributes to software metrics, e.g. “average test coverage” might be improved by tests for unused code and therefore creating false confidence.

Dead code grows in projects for the following reasons:

  • Only few developers check in their IDE if some element is still in use, when they remove a reference to it.
  • Identifying reliably that a public class or method is “dead code” is not a trivial task and requires deep knowledge about the code base.
  • Removing seemingly dead code can easily lead to new bugs therefore developers are usually reluctant to remove them.

It is likely that more dead code exists in large and long running projects with a high fluctuation of developers.

Detecting dead code is a good use case to illustrate Sonargraph Explorer’s powerful scripting API and to demonstrate how it can be used to efficiently detect dead code within a Java project including public classes, methods and fields.