code: public static void assertAllAreNull(String messageIfNull, Object... objects) throws IllegalArgumentException {
          for (Object object : objects) {
              if (object != null) {
                  throw new IllegalArgumentException(messageIfNull);
              }
          }
      }
docs: Asserts that all of the objects are null.
  
  @throws IllegalArgumentException
  if any object provided was NOT null.