* aren't annotated nullable (according to the rules of {@link NullPointerTester}). In details:
   *
   * <ul>
   *   <li>All non-private static methods are checked such that passing null for any parameter
   *       that's not annotated nullable should throw {@link NullPointerException}.
   *   <li>If there is any non-private constructor or non-private static factory method declared by