code: public static boolean isBlank(@Nullable String string) {
          if (isEmpty(string)) {
              return true;
          }
          for (int i = 0; i < string.length(); i++) {
              if (!Character.isWhitespace(string.charAt(i))) {
                  return false;
              }
          }
          return true;
      }
docs: Check if the String is null or has only whitespaces.
  
  Modified from {@link org.apache.commons.lang.StringUtils#isBlank(String)}.
  
  @param string String to check
  @return {@code true} if the String is null or has only whitespaces