Extracting code clones for refactoring using combinations of clone metrics

Code clone detection tools may report a large number of code clones, while software developers are interested in only a subset of code clones that are relevant to software development tasks such as refactoring. Our research group has supported many software developers with the code clone detection tool CCFinder and its GUI front-end Gemini. Gemini shows clone sets (i.e., a set of code clones identical or similar to each other) with several clone metrics including their length and the number of code clones; however, it is not clear how to use those metrics to extract interesting code clones for developers. In this paper, we propose a method combining clone metrics to extract code clones for refactoring activity. We have conducted an empirical study on a web application developed by a Japanese software company. The result indicates that combinations of simple clone metric is more effective to extract refactoring candidates in detected code clones than individual clone metric.