An Empirical Study of Overriding in Open Source Java

Tempero, E., Counsell, S. and Noble, J.

Inheritance is a key feature of object-oriented programming. Overriding is one of the most important parts of inheritance, allowing a subclass to replace methods implemented in its superclass. Unfortunately, the way programmers use overriding in practise is not well understood. We present the first large-scale empirical study of overriding. We describe a suite of metrics that measure overriding and present a corpus analysis that uses those metrics to analyse 100 open-source applications, containing over 100,000 separate classes and interfaces. We found substantial overriding: most subclasses override at least one method and many classes that only declare overriding methods. We also found questionable uses of overriding, such as removing superclass method implementations by overriding them with empty method bodies.

Cite as: Tempero, E., Counsell, S. and Noble, J. (2010). An Empirical Study of Overriding in Open Source Java. In Proc. 33rd Australasian Computer Science Conference (ACSC 2010) Brisbane, Australia. CRPIT, 102. Mans, B. and Reynolds, M. Eds., ACS. 3-12

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