Automatically producing behavioral exception (BE) API documentation helps developers correctly use the libraries. The state-of-the-art approaches are either rule-based, which is too restrictive in its applicability, or deep learning (DL)-based, which requires large training dataset. To address that, we propose StatGen, a novel hybrid approach between statistical machine translation (SMT) and tree-structured translation to generate the BE documentation for any code and vice versa. We consider the documentation and source code of an API method as the two abstraction levels of the same intent. StatGen is specifically designed for this two-way inference, and takes advantage of their structures for higher accuracy.

Statistical language models (LMs) have been applied in several software engineering applications. However, they have issues in dealing with ambiguities in the names of program and API elements (classes and method calls). In this paper, inspired by the success of Deep Neural Network (DNN) in natural language processing, we present Dnn4C, a DNN language model that complements the local context of lexical code elements with both syntactic and type contexts. We designed a context-incorporating method to use with syntactic and type annotations for source code in order to learn to distinguish the lexical tokens in different syntactic and type contexts. Our empirical evaluation on code completion for real-world projects shows that Dnn4C relatively improves 11.6%, 16.3%, 27.1%, and 44.7% top-1 accuracy over the state-of-the-art language models for source code used with the same features: RNN LM, DNN LM, SLAMC, and n-gram LM, respectively. For another application, we showed that Dnn4C helps improve accuracy over n-gram LM in migrating source code from Java to C# with a machine translation model.

Word2Vec is a class of neural network models that as being trainedfrom a large corpus of texts, they can produce for each unique word acorresponding vector in a continuous space in which linguisticcontexts of words can be observed. In this work, we study thecharacteristics of Word2Vec vectors, called API2VEC or API embeddings, for the API elements within the API sequences in source code. Ourempirical study shows that the close proximity of the API2VEC vectorsfor API elements reflects the similar usage contexts containing thesurrounding APIs of those API elements. Moreover, API2VEC can captureseveral similar semantic relations between API elements in API usagesvia vector offsets. We demonstrate the usefulness of API2VEC vectorsfor API elements in three applications. First, we build a tool thatmines the pairs of API elements that share the same usage relationsamong them. The other applications are in the code migrationdomain. We develop API2API, a tool to automatically learn the APImappings between Java and C# using a characteristic of the API2VECvectors for API elements in the two languages: semantic relationsamong API elements in their usages are observed in the two vectorspaces for the two languages as similar geometric arrangements amongtheir API2VEC vectors. Our empirical evaluation shows that API2APIrelatively improves 22.6% and 40.1% top-1 and top-5 accuracy over astate-of-the-art mining approach for API mappings. Finally, as anotherapplication in code migration, we are able to migrate equivalent APIusages from Java to C# with up to 90.6% recall and 87.2% precision.