code: public static void doesNotContain(String textToSearch, String substring, String message) {
          if (Strings.hasLength(textToSearch) && Strings.hasLength(substring) &&
              textToSearch.indexOf(substring) != -1) {
              throw new IllegalArgumentException(message);
          }
      }
docs: Assert that the given text does not contain the given substring.
  <pre class="code">Assert.doesNotContain(name, "rod", "Name must not contain 'rod'");</pre>
  @param textToSearch the text to search
  @param substring the substring to find within the text
  @param message the exception message to use if the assertion fails