Hello, Looking in http://repo1.maven.org/maven2/org/apache/maven/plugins/maven-pmd-plugin/2.3/maven-pmd-plugin-2.3.pom I found out it depends on pmd-jdk14-4.1.1.jar Now, this Jar does not contain net.sourceforge.pmd.rules.basic.AvoidMultipleUnaryOperators but the plugin implementation is looking for it. But, if your use pmd-4.2.1.jar (from http://repo1.maven.org/maven2/pmd/pmd/4.2.1) instead of pmd-jdk14-4.1.1.jar (by manually replacing in ~/.m2/repository), the class is found and everything works. So the problem really is a wrong dependency in maven-pmd-plugin-2.3.pom, which is the latest for this plugin.
FYI --Amir
