Introduction

The program ckjm calculates Chidamber and Kemerer object-oriented metrics by processing the bytecode of compiled Java files. The program calculates for each class the following six metrics, and displays them on its standard output, following the class's name:

WMC: Weighted methods per class
DIT: Depth of Inheritance Tree
NOC: Number of Children
CBO: Coupling between object classes
RFC: Response for a Class
LCOM: Lack of cohesion in methods
Ca: Afferent coupling (not a C&K metric)
NPM: Number of Public Methods for a class (not a C&K metric)

I wrote this program out of frustration over the lack of reliable programs to calculate the Chidamber and Kemerer object-oriented metrics. The programs I found on the web were either incomplete (they calculated only some of the metrics), or unreliable (they calculated results that were obviously wrong), or extremely inefficient (they required GBs of RAM and hours of processing). Ckjm is mean and lean, following the Unix tradition of doing one thing well. It will not automatically recurse directories looking for the files you want measured, it does not offer a GUI and fancy diagrams (or even an XML output facility), and it calculates only few metrics other than the six ones specified by Chidamber and Kemerer. However, it does this job thoroughly, and efficiently: on a 1.6GHz Pentium-M machine version 1.1 of the tool processed the 33MB of the Eclipse 3.0 jar files (19717 classes) in 95 seconds.

To run the program you simply specify the class files (or pairs of jar/class files) on its command line or standard input. The program will produce on its standard output a line for each class containing the complete name of the class and the values of the corresponding class metrics. This operation model allows the tool to be easilly extended using textual pre and post processors.

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