Characterizing the Usage, Evolution and Impact of Java Annotations in Practice

TL;DR

This paper presents a large-scale empirical study of Java annotations in open-source projects, revealing their usage patterns, evolution, and impact on code quality, providing insights for developers and language designers.

Contribution

It is the first comprehensive empirical analysis of Java annotations, covering their usage, evolution, and impact across over a thousand open-source projects.

Findings

Annotations are widely used for various purposes in Java projects.

Annotations evolve significantly during software development.

Annotations have a measurable impact on code quality.

Abstract

Annotations have been formally introduced into Java since Java 5. Since then, annotations have been widely used by the Java community for different purposes, such as compiler guidance and runtime processing. Despite the ever-growing use, there is still limited empirical knowledge about the actual usage of annotations in practice, the changes made to annotations during software evolution, and the potential impact of annotations on code quality. To fill this gap, we perform the first large-scale empirical study about Java annotations on 1,094 notable open-source projects hosted on GitHub. Our study systematically investigates annotation usage, annotation evolution, and annotation impact, and generates 10 novel and important findings. We also present the implications of our findings, which shed light for developers, researchers, tool builders, and language or library designers in order to improve all facets of Java annotation engineering.