code: public static Iterator<String> iterateClassnames(final File parentDirectory,
                                                     final File ... classFiles) {
      return iterateClassnames(parentDirectory, Arrays.asList(classFiles).iterator());
    }
docs: Iterate over the class files and remove the parent directory from file name and replace
  directory separator with dots.
  
  @param parentDirectory to remove from {@code classFile} and maybe {@code null}.
  @param classFiles array to extract the names from. Must not be {@code null}.
  @return iterator of full qualified class names based on passed classFiles
  @see #iterateClassnames(File, Iterator)