Characterizing Java Streams in the Wild

Since Java 8, streams ease the development of data transformations using a declarative style based on functional programming. Some recent studies aim at shedding light on how streams are used. However, they consider only small sets of applications and mainly apply static analysis techniques, leaving the large-scale analysis of dynamic metrics focusing on stream processing an open research question. In this paper, we present the first large-scale empirical study on the use of streams in Java. We present a novel dynamic analysis for collecting runtime information and key metrics that enable the fine-grained characterization of sequential and parallel stream processing. We massively apply our dynamic analysis using a fully automated approach, supported by a distributed infrastructure to mine public software projects hosted on GitHub. Our findings advance the understanding of the use of streams, both confirming some of the results of previous studies at a much larger scale, as well as revealing previously unobserved findings in the use of streams.