docs: private static String toFullWidth(String ascii) {
      int numChars = ascii.length();
      StringBuilder sb = new StringBuilder(ascii);
      for (int i = 0; i < numChars; ++i) {
        char ch = ascii.charAt(i);
        if (ch < 0x80) {
          sb.setCharAt(i, (char) (ch + 0xff00 - 0x20));
        }
      }
      return sb.toString();
    }