code: public static <T extends CharSequence> T defaultIfBlank(T str, T defaultStr) {
      return isBlank(str) ? defaultStr : str;
    }
docs: <p>
  Returns either the passed in CharSequence, or if the CharSequence is whitespace, empty ("") or
  {@code null}, the value of {@code defaultStr}.
  </p>
  
  @param str
  @param defaultStr