Empirical Evidence of Large-Scale Diversity in API Usage of Object-Oriented Software

TL;DR

This paper provides empirical evidence that object-oriented classes exhibit significant usage diversity across thousands of software packages, impacting software engineering practices and research.

Contribution

It introduces the concept of usage diversity and quantifies it for various classes, highlighting its implications for software engineering.

Findings

Java's String class has 2460 different usage patterns.

Many classes show high usage diversity, indicating complex usage scenarios.

Diversity affects software design, testing, and documentation.

Abstract

In this paper, we study how object-oriented classes are used across thousands of software packages. We concentrate on "usage diversity'", defined as the different statically observable combinations of methods called on the same object. We present empirical evidence that there is a significant usage diversity for many classes. For instance, we observe in our dataset that Java's String is used in 2460 manners. We discuss the reasons of this observed diversity and the consequences on software engineering knowledge and research.