An Empirical Study of Fan-In and Fan-Out in Java OSS

Coupling is a well researched topic in the Object-Oriented (OO) research community and its influence on class cohesion is well understood. In this paper, we present an empirical study exploring the effect of method calling on class cohesion using two coupling metrics, namely fan-in and fan-out. Three Java, open-source systems (OSS) were used as a basis of the study. A small number of classes were found to account for the vast majority of fan-in and fan-out. We also found the impact of fan-out on class cohesion to be higher than that of fan-in. Classes containing fan-out tended to have lower cohesion than those containing fan-in.