new Object() {
                  @Override
                  public String toString() {
                    return "I'm a string";
                  }
                }));
    assertThrows(NullPointerException.class, () -> Functions.toStringFunction().apply(null));
  }

  @J2ktIncompatible
  @GwtIncompatible // SerializableTester
  public void testToStringFunctionSerializable() {

   * @throws IllegalArgumentException if the size of the cartesian product would be greater than
   *     {@link Integer#MAX_VALUE}
   * @throws NullPointerException if {@code lists}, any one of the {@code lists}, or any element of
   *     a provided list is null
   * @since 19.0
   */
  public static <B> List<List<B>> cartesianProduct(List<? extends List<? extends B>> lists) {

            buffer = new DfsReferralRequestBuffer(path, maxReferralLevel);
            assertNotNull(buffer);

            // Will throw NPE when trying to call size() or encode()
            assertThrows(NullPointerException.class, () -> {
                buffer.size();
            });
        }

        @ParameterizedTest
        @DisplayName("Should handle various referral levels")

    assertThat(reMultisetFirst.a.isEmpty()).isFalse();
    // The following NPE is a side effect of our changes to avoid mutating `final` fields.
    assertThrows(NullPointerException.class, () -> reMultisetFirst.z.multiset.isEmpty());

    ContainsBothWithContainsMultisetFirst reContainsMultisetFirst =
        reserialize(containsMultisetFirst);

     *         obtained, the returned version range's recommended version is set to <code>null</code>.
     *         </p>
     * @throws NullPointerException if the specified <code>VersionRange</code> is
     *                              <code>null</code>.
     */
    public VersionRange restrict(VersionRange restriction) {

   *   <li>All visible static methods are checked such that passing null for any parameter that's
   *       not annotated nullable (according to the rules of {@link NullPointerTester}) should throw
   *       {@link NullPointerException}.
   *   <li>If there is any visible constructor or visible static factory method declared by the
   *       class, all visible instance methods will be checked too using the instance created by

    List<@Nullable Integer> values = Arrays.asList(1, null);
    assertThrows(
        NullPointerException.class,
        () -> Multimaps.index((List<Integer>) values, Functions.identity()));
  }

  public void testIndex_nullKey() {
    List<Integer> values = Arrays.asList(1, 2);
    assertThrows(
        NullPointerException.class, () -> Multimaps.index(values, Functions.constant(null)));
  }

      AvlNode<E> root = rootReference.get();
      if (!range.contains(e) || root == null) {
        return 0;
      }
      return root.count(comparator(), e);
    } catch (ClassCastException | NullPointerException e) {
      return 0;
    }
  }

  @CanIgnoreReturnValue
  @Override
  public int add(@ParametricNullness E element, int occurrences) {
    checkNonnegative(occurrences, "occurrences");

     *
     * @param dest
     *            An <code>SmbResource</code> that represents the new pathname
     * @throws CIFSException if an error occurs renaming the resource
     * @throws NullPointerException
     *             If the <code>dest</code> argument is <code>null</code>
     */
    void renameTo(SmbResource dest) throws CIFSException;

    /**

   * necessary.
   *
   * <p>The returned iterator supports {@code remove()} when the corresponding input iterator
   * supports it.
   *
   * @throws NullPointerException if any of the provided iterators is null
   */
  @SafeVarargs
  public static <T extends @Nullable Object> Iterator<T> concat(Iterator<? extends T>... inputs) {