The loose coupling design principle is to restrict the interactions among modules and therefore contain the changes local to the modules themselves. It can always be regarded as an indicator of good design quality in terms of software maintenance. In order to maintain source code in software systems, it is crucial and always helpful to identify the coupling relationships among classes. Although efforts have been made on developing metrics of coupling strength between modules, little emphasis has been put on investigating the strength of coupling between Java classes. In this work, we explore the coupling relationships among Java classes based on an extension to a coupling framework proposed by Hitz and Montazeri.