code: public static boolean containsWhitespace(final String str) {
          if (N.isNullOrEmpty(str)) {
              return false;
          }
  
          final char[] chars = getCharsForReadOnly(str);
          for (int i = 0, len = str.length(); i < len; i++) {
              if (Character.isWhitespace(chars[i])) {
                  return true;
              }
          }
  
          return false;
      }
docs: From org.springframework.util.StringUtils, under Apache License 2.0