docs: private int getAndParseHexChar() throws ParseException {
          final char hexChar = getc();
          if (hexChar >= '0' && hexChar <= '9') {
              return hexChar - '0';
          } else if (hexChar >= 'a' && hexChar <= 'f') {
              return hexChar - 'a' + 10;
          } else if (hexChar >= 'A' && hexChar <= 'F') {
              return hexChar - 'A' + 10;
          } else {
              throw new ParseException(this, "Invalid character in Unicode escape sequence: " + hexChar);
          }
      }