Abstract
Background: The Java programming language version eight introduced several features that encourage the functional style of programming, including the support for lambda expressions and the Stream API. Currently, there is common wisdom that refactoring legacy code to introduce lambda expressions, besides other potential benefits, simplifies the code and improves program comprehension. Aims: The purpose of this work is to investigate this belief, conducting an in-depth study to evaluate the effect of introducing lambda expressions on program comprehension. Method: We conduct this research using a mixed-method study. For the quantitative method, we quantitatively analyze 166 pairs of code snippets extracted directly either from GitHub or from recommendations from three tools (RJTL, NetBeans, and IntelliJ). We also surveyed practitioners to collect their perceptions about the benefits on program comprehension when introducing lambda expressions. We asked practitioners to evaluate and rate sets of pairs of code snippets. Results: We found contradictory results in our research. Based on the quantitative assessment, we could not find evidence that the introduction of lambda expressions improves software readability—one of the components of program comprehension. Our results suggest that the transformations recommended by the aforementioned tools decrease program comprehension when assessed by two state-of-the-art models to estimate readability. Differently, our findings of the qualitative assessment suggest that the introduction of lambda expression improves program comprehension in three scenarios: when we convert anonymous inner classes to a lambda expression, structural loops with inner conditional to a anyMatch operator, and structural loops to filter operator combined with a collect method. Implications: We argue in this paper that one can improve program comprehension when she applies particular transformations to introduce lambda expressions (e.g., replacing anonymous inner classes with lambda expressions). Also, the opinion of the participants shines the opportunities in which a transformation for introducing lambda might be advantageous. This might support the implementation of effective tools for automatic program transformations.
Highlights
Software evolves to adapt to social and technical needs (God frey and German, 2008): users might request new features, or performance constraints must be met
Our findings of the qualitative assessment suggest that the introduction of lambda expression improves program comprehension in three scenarios when: we convert anonymous inner classes to a lambda expression, use structural loops with inner conditional to an anyMatch operator, and apply structural loops to filter operator combined with a collect method
Implications: We argue in this paper that one can improve program comprehension when he/she applies particular transformations to introduce lambda expressions
Summary
Software evolves to adapt to social and technical needs (God frey and German, 2008): users might request new features, or performance constraints must be met. Understanding ex isting software enables maintainers to successfully evolve functionality and/or integrate improvements for every type of change commonly associated with software maintenance and evolution, including adaptive, perfective, and correc tive modifications (von Mayrhauser and Vans, 1995). While it is true that the skills and experiences of a developer are relevant when he/she wants to understand software, it has been reported that a set of recommended practices (such as the use of programming idioms and code formatting tools, design patterns, and refactoring) might support program comprehension, in particular when using a bottomup strategy as defined by Pennington (1987). The atoms of confusion conditional operator and logical as con trol flow involve fundamental language constructs such as math operators and if statements
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