The OO versions were implemented in Java, whereas the AO versions were implemented in AspectJ. The design stability evaluation of the Java and AspectJ versions were based on two conventional metric suites for modularity attributes (such as separation of concerns, coupling, and conciseness)and change impact.Hence, our investigation complements in two senses the existing well-known qualitative empirical study on the use of AO for implementing design by contract concern performed by Lippert and Lopes work