A Duplicated Code Refactoring Advisor

Refactoring is one of the key practices in Extreme Programming and other agile methods. Duplicated code is one of the most pervasive and pungent smells to remove from source code through refactoring. Duplicated code has been largely studied in the literature, and different types of duplications, or “clones”, have been identified. Some studies analyzed in details the problems caused by clones in the code, others outlined also the difficulties in removing clones, and the cases in which it could be better not removing them. The refactoring cost for removing clones can be very high, also due to the different choices on the possible refactoring steps. In this paper, we describe our approach and tool developed with the aim to suggest the best refactorings to remove clones in Java code. Our approach is based on the classification of the clones in terms of their location in a class hierarchy, and allows to choose among a restricted set of refactorings, which are then evaluated using multiple criteria. We provide a validation of the effectiveness of the approach.