Fast-ClassPath-Scanner does not work with java 6 runtime?

Fast-ClassPath-Scanner http://ift.tt/1sdNsRi using latest version. On executing(get names of all classes in war which includes all jars and classes)

new FastClasspathScanner(basePackage).scan().getNamesOfAllClasses()

getting unsupportedclassversion error with jre 6 .

Please provide a solution to it or alternative to perform same.