Reconciling the Past and the Present: An Empirical Study on the Application of Source Code Transformations to Automatically Rejuvenate Java']Java Programs

Software systems change frequently over time, either due to new business requirements or technology pressures. Programming languages evolve in a similar constant fashion, though when a language release introduces new programming constructs, older constructs and idioms might become obsolete. The coexistence between newer and older constructs leads to several problems, such as increased maintenance efforts and steeper learning curve for developers. In this paper we present a RASCAL Java transformation library that evolves legacy systems to use more recent programming language constructs (such as multi-catch and lambda expressions). In order to understand how relevant automatic software rejuvenation is, we submitted 2462 transformations to 40 open source projects via the GitHub pull request mechanism. Initial results show that simple transformations, for instance the introduction of the diamond operator, are more likely to be accepted than transformations that change the code substantially, such as refactoring enhanced for loops to the newer functional style.