Domino Effect: Move More Methods Once A Method Is Moved

Software refactoring is a popular technology to improve the design of existing source code, and thus it is widely used to facilitate software evolution. Moving methods is one of the most popular refactorings. It helps to reduce coupling between classes and to improve cohesion of involved classes. However, it is difficult to manually identify such methods that should be moved. Consequently, a number of approaches and tools have been proposed to identify such methods based on source code metrics, change history, and textual information. In this paper we propose a new way to identify methods that should be moved. Whenever a method is moved, the approach checks other methods within the same class, and suggests to move the one with the greatest similarity and strongest relationship with the moved method. The rational is that similar and closely related methods should be moved together. The approach has been evaluated on open-source applications by comparing the recommended move method refactorings against refactoring histories of the involved applications. Our evaluation results show that the approach is accurate in recommending methods to be moved (average precision 76%) and in recommending destinations for such methods (average precision 83%). Our evaluation results also show that for a substantial percentage (27%) of move method refactorings, the proposed approach succeeds in identifying additional refactoring opportunities.