This paper presents an analysis of the evolution of an open source software system, JFreeChart, which is an open source charting library [1], based on its size, fan-in/out coupling, and cohesion metrics. We developed JamTool, a Java automated measurement tool [4] to obtain the metrics and to observe the quality change along the evolution of the twenty-two released versions of JFreeChart. The empirical study clearly indicates that there are positive relations between the number of classes and the fan-in/out coupling, and the added class group has better software quality than the removed class group. Moreover, the experimental results follow Lehman's 1 st , 2 nd , 6 th  laws 6 th  but against 7 th  law of software evolution.
['Young Lee', 'Jeong Yang', 'Kai H. Chang']
Metrics and Evolution in Open Source Software