What is Class Complexity

Design patterns are standardized solutions to commonly encountered problems using the object-oriented programming paradigm. Applying design patterns can speed up software development processes through the reuse of tested, proven templates, or development paradigms. Accordingly, design patterns have been widely used in software industry to build modern software programs. However, as different design patterns are introduced to solve different design problems, they are not necessarily superior to alternative solutions, with respect to all aspects of software design. One major concern is that the inappropriate use of design patterns may unnecessarily increase program complexity, such as class structural quality. Theoretical analysis of the effect of design patterns on software complexity has been widely performed. However, little work is reported to empirically study how design patterns might affect class structural quality. This chapter studies six components from five open-source Java projects and empirically investigates if design patterns can affect class structural quality. The chapter finds that pattern-involved classes are more complex than pattern-free classes and recommends the cautious use of design patterns to avoid unnecessary increases in class complexity and decrease in class structural quality.