Moonstone: Support for Understanding and Writing Exception Handling Code

Moonstone is a new plugin for Eclipse that supports developers in understanding exception flow and in writing exception handlers in Java. Understanding exception control flow is paramount for writing robust exception handlers, a task many developers struggle with. To help with this understanding, we present two new kinds of information: ghost comments, which are transient overlays that reveal potential sources of exceptions directly in code, and annotated highlights of skipped code and associated handlers. To help developers write better handlers, Moonstone additionally provides project-specific recommendations, detects common bad practices, such as empty or inadequate handlers, and provides automatic resolutions, introducing programmers to advanced Java exception handling features, such as try-with-resources. We present findings from two formative studies that informed the design of Moonstone. We then show with a user study that Moonstone improves users' understanding in certain areas and enables developers to amend exception handling code more quickly and correctly.