Exception evolution in long-lived Java systems.

Exception handling allows developers to deal with abnormal situations that disrupt the execution flow of a program. There are mainly three types of exceptions: standard exceptions provided by the programming language itself, custom exceptions defined by the project developers, and third-party exceptions defined in external libraries. We conjecture that there are multiple factors that affect the use of these exception types. We perform an empirical study on long-lived Java projects to investigate these factors. In particular, we analyze how developers rely on the different types of exceptions in throw statements and exception handlers. We confirm that the domain, the type, and the development phase of a project affect the exception handling patterns. We observe that applications have significantly more error handling code than libraries and they increasingly rely on custom exceptions. Also, projects that belong to different domains have different preferences of exception types. For instance, content management systems rely more on custom exceptions than standard exceptions whereas the opposite is true in parsing frameworks.