code: private static boolean accept(final String extension, final File pathname) {
          if (nulls(extension, pathname)) return false;
          String absPath = pathname.getAbsolutePath();
          final int extLength = extension.length();
          int start = absPath.length() - extLength, end = absPath.length();
          String ext = absPath.substring(start, end);
          if (extension.equalsIgnoreCase(ext)) return true;
          return false;
      }
docs: Returns {@code true} if {@code pathname} ends with {@code extension},
  ignoring case, {@code false} otherwise.
  
  @param extension File extension
  @param pathname Path name
  @return boolean