  Nowadays, developers often reuse existing APIs to implement their programming
tasks. A lot of API usage patterns are mined to help developers learn API usage
rules. However, there are still many missing variables to be synthesized when
developers integrate the patterns into their programming context. To deal with
this issue, we propose a comprehensive approach to integrate API usage patterns
in this paper. We first perform an empirical study by analyzing how API usage
patterns are integrated in real-world projects. We find the expressions for
variable synthesis is often non-trivial and can be divided into 5 syntax types.
Based on the observation, we promote an approach to help developers
interactively complete API usage patterns. Compared to the existing code
completion techniques, our approach can recommend infrequent expressions
accompanied with their real-world usage examples according to the user intent.
The evaluation shows that our approach could assist users to integrate APIs
more efficiently and complete the programming tasks faster than existing works.
