assertEquals(2, (int) result.next());
    assertThrows(NullPointerException.class, () -> result.hasNext());
    assertThrows(NullPointerException.class, () -> result.next());
    // There is no way to get "through" to the 3.  Buh-bye
  }

  public void testConcatVarArgsContainingNull() {
    assertThrows(
        NullPointerException.class,
        () ->
            Iterators.concat(

            return "RAW";
          }
        };
    try {
      Hashing.hmacMd5(badKey);
      fail();
    } catch (IllegalArgumentException expected) {
    } catch (NullPointerException toleratedOnAndroid) {
      // TODO(cpovirk): In an ideal world, we'd check here that we're running on Android.
    }
  }

  public void testEmptyInputs() throws Exception {

   * safe to do so. The exact circumstances under which a copy will or will not be performed are
   * undocumented and subject to change.
   *
   * @throws NullPointerException if any key or value in {@code multimap} is null
   */
  public static <K, V> ImmutableSetMultimap<K, V> copyOf(
      Multimap<? extends K, ? extends V> multimap) {
    return copyOf(multimap, null);
  }

 *  Fix: Don't close a `Deflater` while we're still using it to compress a web socket message. We
    had a severe bug where web sockets were closed on the wrong thread, which caused
    `NullPointerException` crashes in `Deflater`.

 *  Fix: Don't crash after a web socket fails its connection upgrade. We incorrectly released
    the web socket's connections back to the pool before their resources were cleaned up.

   * possible.
   *
   * @param sources the sources to concatenate
   * @return a {@code ByteSource} containing the concatenated data
   * @throws NullPointerException if any of {@code sources} is {@code null}
   * @since 15.0
   */
  public static ByteSource concat(Iterator<? extends ByteSource> sources) {
    return concat(ImmutableList.copyOf(sources));
  }

  /**

   *
   * @param collection a collection of {@code Character} objects
   * @return an array containing the same values as {@code collection}, in the same order, converted
   *     to primitives
   * @throws NullPointerException if {@code collection} or any of its elements is null
   */
  public static char[] toArray(Collection<Character> collection) {
    if (collection instanceof CharArrayAsList) {

    return asImmutableList(array);
  }

  private static <E> List<E> nullCheckedList(Object... array) {
    for (int i = 0, len = array.length; i < len; i++) {
      if (array[i] == null) {
        throw new NullPointerException("at index " + i);
      }
    }
    @SuppressWarnings("unchecked")
    E[] castedArray = (E[]) array;
    return Arrays.asList(castedArray);
  }

  @Override

   *   <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

    assertEquals(2, (int) result.next());
    assertThrows(NullPointerException.class, () -> result.hasNext());
    assertThrows(NullPointerException.class, () -> result.next());
    // There is no way to get "through" to the 3.  Buh-bye
  }

  public void testConcatVarArgsContainingNull() {
    assertThrows(
        NullPointerException.class,
        () ->
            Iterators.concat(

      List<E> extremeValues = new ArrayList<>();

      // nulls are usually out of bounds for a subset, so ban them altogether
      for (Object o : elements) {
        if (o == null) {
          throw new NullPointerException();
        }
      }

      // prepare extreme values to be filtered out of view
      E firstExclusive = delegate.belowSamplesGreater();
      E lastExclusive = delegate.aboveSamplesLesser();