code: static String[] getClasspathClassNames() throws ZipException, IOException {
          final String[] classes = getClasspathFileNamesWithExtension(".class");
          for (int i = 0; i < classes.length; i++) {
              classes[i] = classes[i].substring(0, classes[i].length() - 6).replace("/", ".");
          }
          return classes;
      }
docs: Returns a list of the classes on the
  classpath. The names returned will
  be appropriate for using Class.forName(String)
  in that the slashes will be changed to dots
  and the .class file extension will be removed.