A Large-scale Empirical Study of Java Language Feature Usage

Programming languages evolve over time, adding additional language features to simplify common tasks and make the language easier to use. For example, the Java Language Specification has four editions and is currently drafting a fifth. While the addition of language features is driven by an assumed need by the community (often with direct requests for such features), there is little empirical evidence demonstrating how these new features are adopted by developers once released. In this paper, we analyze over 23k open-source Java projects representing over 7 million Java files, which when parsed contain over 14 billion AST nodes. We analyze this corpus to find uses of new Java language features over time. Our study gives interesting insights, such as: the fact that while all features are used, there are still millions of more places they could potentially be used; all features are used before release; and features tend to be adopted by committers on an individual basis rather than as a team.