code: public static boolean isBlank(final String source) {
  
      if (isEmpty(source)) {
        return true;
      }
      int strLen = source.length();
      for (int i = 0; i < strLen; i++) {
        if (!Character.isWhitespace(source.charAt(i))) {
          return false;
        }
      }
      return true;
    }
docs: Returns true if the source string is null or all characters in this string
  is space; false otherwise.
  
  @param source string to be tested.
  @return true if the source string is null or all characters in this string
  is space; false otherwise.