Identifiers in source code are composed of terms in natural languages. Such terms, as well as phrases composed of such terms, convey rich semantics that could be exploited for program analysis and comprehension. To this end, in this paper we propose a deep learning based approach, called MLDetector, to identifying suspicious return statements by leveraging semantics conveyed by the natural language phrases that are used as identifiers in the source code. We specially design a deep neural network to tell whether a given return statement matches its corresponding method signature. The rationale is that both method signature and return value should explicitly specify the output of the method, and thus a significant mismatch between method signature and return value may suggest a suspicious return statement. To address the challenge of lacking negative training data, i.e., incorrect return statements, we generate negative training data automatically by transforming real-world correct return statements. To feed code into neural network, we convert them into vectors by Word2Vec, an unsupervised neural network based learning algorithm. We evaluate the proposed approach in two parts. In the first part, we evaluate it on 500 open-source applications by automatically generating labeled training data. Results suggest that the precision of the proposed approach varies from 83% to 90%. In the second part, we conduct a case study on 100 real-world applications. Evaluation results suggest that 42 out of 65 real-world incorrect return statements are detected (with precision of 59%).

Software systems often receive a large number of bug reports. Triagers read through such reports and assign different priorities to different reports so that important and urgent bugs could be fixed on time. However, manual prioritization is tedious and time-consuming. To this end, in this article, we propose a convolutional neural network (CNN) based automatic approach to predict the multiclass priority for bug reports. First, we apply natural language processing (NLP) techniques to preprocess textual information of bug reports and covert the textual information into vectors based on the syntactic and semantic relationship of words within each bug report. Second, we perform the software engineering domain specific emotion analysis on bug reports and compute the emotion value for each of them using a software engineering domain repository. Finally, we train a CNN-based classifier that generates a suggested priority based on its input, i.e., vectored textual information and emotion values. To the best of our knowledge, it is the first CNN-based approach to bug report prioritization. We evaluate the proposed approach on open-source projects. Results of our cross-project evaluation suggest that the proposed approach significantly outperforms the state-of-the-art approaches and improves the average F1-score by more than 24%.

During software evolution, developers often receive new requirements expressed as feature requests. To implement the requested features, developers have to perform necessary modifications (refactorings) to prepare for new adaptation that accommodates the new requirements. Software refactoring is a well-known technique that has been extensively used to improve software quality such as maintainability and extensibility. However, it is often challenging to determine which kind of refactorings should be applied. Consequently, several approaches based on various heuristics have been proposed to recommend refactorings. However, there is still lack of automated support to recommend refactorings given a feature request. To this end, in this paper, we propose a novel approach that recommends refactorings based on the history of the previously requested features and applied refactorings. First, we exploit the stateof-the-art refactoring detection tools to identify the previous refactorings applied to implement the past feature requests. Second, we train a machine classifier with the history data of the feature requests and refactorings applied on the commits that implemented the corresponding feature requests. The machine classifier is then used to predict refactorings for new feature requests. We evaluate the proposed approach on the dataset of 43 open source Java projects and the results suggest that the proposed approach can accurately recommend refactorings (average precision 73%).