Abstract: Code query plays an important role in code reuse,and the Q&A about code on StackOverflow which is a professionalquestion-and-answer site for programmers is a typical scenario for code reuse.In practice,the manual way is adopted to answer questions,which usually has the disadvantages of poor real-time,incorrect description of problems,and low availability of answers.If the process of code query and search can be automated and replace manual answering, it will save a lot of manpower and time cost.Now there are already many code query technologies,but most lack experie-nce of application in the real case.Based on the ideas of Satsy,this paper implemented the code query technology based on constraint solving for Java language,and designed the empirical study.This paper used StackOverflow as the research object,and mainly studied how to apply the code query technology based on constraint solving of Q&A about code on the website.First of all,the problems on the website are analyzed,and 35 problems with high trafficin Java language are extracted as query problems.Then,about 30000 lines of code are captured from GitHub,and they are converted into the form of constraints as well as built as a large code base to support code query.Finally,through the analysis of the query results of these 35 questions,the practical application effect of the technology on StackOverflow was evalua-ted.The results show that the proposed technology has good practical application effect on the specific questions and code scale studied,and can replace the manual answer on a considerable scale.

Key words: Code query, Constraint solving, Empirical study, Opensource code database