docs: private static boolean isValidChar(char c) {
          if ( c >= '0' && c <= '9' || c >= 'A' && c <= 'Z' || c >= 'a' && c <= 'z' ) {
              return true;
          }
          return c != ' ' && c != '\u00A0' && !Character.isWhitespace(c) && !Character.isWhitespace(c);
      }