Abstract: Long method is a software design problem that requires refactoring because it is too long.In order to improve the detection rate of traditional machine learning approaches on long method,a cost-sensitive integrated classifier algorithm was proposed from the viewpoint of unbalanced sample data of code smell.Based on the traditional decision tree algorithm,the under-sampling startegy is used for resampling,then a plurality of balanced subsets are generated.These subsets are trained to generate a plurality of same base classifiers.Finally,the mistaken classification cost determined by the cognitive complexity is complemented to the integrated classifier.The cost makes the classifier inclined to the accuracy rate of the minority categories.Compared with the traditional machine learning algorithm,this method has improved the precision and recall for detection result of long methods.

Key words: Code smell, Cognitive complexity, Cost-sensitive, Long method