Functional Classes: Cost of Recursive Method Call in Java

In this paper, we discuss the cost of functional classes design style. Functional classes merge both object-oriented and functional programming paradigms; a functional class is a class without variables. Because of this, the methods in functional classes are true functions. Functional classes design style aims at improving reliability and program correctness. However, resulting program code is not optimal when considering the performance. As the main contribution, we analyze here the performance of functional classes in Java. We study especially the cost of recursive method calls. As the case study, we analyze an implementation of the cartesian product operation in a lightweight data mediator. The analysis confirms that functional classes design style leads to implementations that make poor use of HotSpot. However, the analysis also indicates how to restructure a functional class to improve the performance.