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Sun 22 - Fri 27 October 2017 Vancouver, Canada
Thu 26 Oct 2017 14:15 - 14:37 at Regency A - Mining Software Repositories and Parsing Chair(s): Wolfgang De Meuter

Java 8 retrofitted lambda expressions, a core feature of functional programming, into a mainstream object-oriented language with an imperative paradigm. However, we do not know how Java developers have adapted to the functional style of thinking, and more importantly, what are the reasons motivating Java developers to adopt functional programming. Without such knowledge, researchers miss opportunities to improve the state of the art, tool builders use unrealistic assumptions, language designers fail to improve upon their designs, and developers are unable to explore efficient and effective use of lambdas.

We present the first large-scale, quantitative and qualitative empirical study to shed light on how imperative programmers use lambda expressions as a gateway into functional thinking. Particularly, we statically scrutinize the source code of 241 open-source projects with 19,770 contributors, to study the characteristics of 100,540 lambda expressions. Moreover, we investigate the historical trends and adoption rates of lambdas in the studied projects. To get a complementary perspective, we seek the underlying reasons on why developers introduce lambda expressions, by surveying 97 developers who are introducing lambdas in their projects, using the firehouse interview method.

Among others, our findings revealed an increasing trend in the adoption of lambdas in Java: in 2016, the ratio of lambdas introduced per added line of code increased by 54% compared to 2015. Lambdas were used for various reasons, including but not limited to (i) making existing code more succinct and readable, (ii) avoiding code duplication, and (iii) simulating lazy evaluation of functions. Interestingly, we found out that developers are using Java's built-in functional interfaces inefficiently, i.e., they prefer to use general functional interfaces over the specialized ones, overlooking the performance overheads that might be imposed. Furthermore, developers are not adopting techniques from functional programming, e.g., currying. Finally, we present the implications of our findings for researchers, tool builders, language designers, and developers.

Thu 26 Oct

13:30 - 15:00: OOPSLA - Mining Software Repositories and Parsing at Regency A
Chair(s): Wolfgang De MeuterVrije Universiteit Brussel
splash-2017-OOPSLA150901740000013:30 - 13:52
Samantha Syeda KhairunnesaIowa State University, Hoan Anh NguyenIowa State University, USA, Tien NguyenUniversity of Texas at Dallas, Hridesh RajanIowa State University
splash-2017-OOPSLA150901875000013:52 - 14:15
Crista LopesUniversity of California, Irvine, Petr MajReactorLabs, Pedro MartinsUniversity of California at Irvine, USA, Vaibhav SainiUniversity of California at Irvine, USA, Di YangUniversity of California at Irvine, USA, Jakub ZitnyCzech Technical University, Czechia, Hitesh SajnaniMicrosoft , Jan VitekNortheastern University, USA
splash-2017-OOPSLA150902010000014:15 - 14:37
Davood MazinanianConcordia University, Canada, Ameya KetkarOregon State University, USA, Nikolaos TsantalisConcordia University, Canada, Danny DigSchool of EECS at Oregon State University
splash-2017-OOPSLA150902145000014:37 - 15:00
Michael D. AdamsUniversity of Utah, USA, Matthew MightUniversity of Utah, USA