Identification of Extract Method Refactoring Opportunities

Extract method has been recognized as one of the most important refactorings, since it decomposes large methods and can be used in combination with other refactorings for fixing a variety of design problems. However, existing tools and methodologies support extraction of methods based on a set of statements selected by the user in the original method. The goal of the proposed methodology is to automatically identify extract method refactoring opportunities and present them as suggestions to the designer of an object-oriented system. The suggested refactorings adhere to three principles: the extracted code should contain the complete computation of a given variable declared in the original method, the behavior of the program should be preserved after the application of the refactoring, and the extracted code should not be excessively duplicated in the original method. The proposed approach is based on the union of static slices that result from the application of a block-based slicing technique. The soundness of the identified refactoring opportunities has been evaluated by an independent designer on the system that he developed.