On the spread and evolution of dead methods in Java desktop applications: an exploratory study

Background. Dead code is a code smell. It can refer to code blocks, fields, methods, etc. that are unused and/or unreachable-e.g., if a method is unused and/or unreachable, it is a dead method. Past research has shown that the presence of dead code in source code harms its comprehensibility and maintainability. Nevertheless, there is still little empirical evidence on the spread of this code smell in the source code of commercial and open-source software applications.Aims. Our goal is to gather, through an exploratory study, empirical evidence on the spread and evolution of dead methods in open-source Java desktop applications.Method. We quantitatively analyzed the commit histories of 23 open-source Java desktop applications, whose software projects were hosted on GitHub. To investigate the spread and evolution of dead methods, we focused on dead methods detected at a commit level. The total number of analyzed commits in our study is 1,587. The perspective of our exploratory study is that of both practitioners and researchers.Results. We can summarize the most important take-away results as follows: (i) dead methods affect open-source Java desktop applications; (ii) dead methods generally survive for a long time before being "buried" or "revived;" (iii) dead methods that are then revived tend to survive less, as compared to dead methods that are then buried; (iv) dead methods are rarely revived; and (v) most dead methods are stillborn, rather than becoming dead later. Given the exploratory nature of our study, we believe that its results will help researchers to conduct more resource- and time-demanding research on dead methods and, in general, on dead code.Conclusions. We can conclude that developers should carefully handle dead code (and thus dead methods) since it is harmful, widespread, rarely revived, and survives for a long time in software applications.