code: public static List<File> listFilesByRegex(String regex, File... directories) {
          return listFiles(directories,
                  new RegexFileFilter(regex),
                  CanReadFileFilter.CAN_READ);
      }
docs: Returns list of files matches specified regex in specified directories
  
  @param regex       to match file names
  @param directories to find
  @return list of files matches specified regex in specified directories