Debugging

A qualitative analysis of debugging strategies of novice Java programmers is presented. The study involved 21 CS2 students from seven universities in the U.S. and U.K. Subjects "warmed up" by coding a solution to a typical introductory problem. This was followed by an exercise debugging a syntactically correct version with logic errors. Many novices found and fixed bugs using strategies such as tracing, commenting out code, diagnostic print statements and methodical testing. Some competently used online resources and debuggers. Students also used pattern matching to detect errors in code that "just didn't look right". However, some used few strategies, applied them ineffectively, or engaged in other unproductive behaviors. This led to poor performance, frustration for some, and occasionally the introduction of new bugs. Pedagogical implications and suggestions for future research are discussed.