* IllegalArgumentException} is thrown when the collection operation is performed. (This differs
   * from the {@code Collector} returned by {@link Collectors#toMap(Function, Function)}, which
   * throws an {@code IllegalStateException}.)
   *
   * @since 33.2.0 (available since 21.0 in guava-jre)
   */
  @SuppressWarnings({"AndroidJdkLibsChecker", "Java7ApiChecker"})

    try {
      Maps.toMap((Iterable<String>) strings, Functions.constant("foo"));
      fail();
    } catch (NullPointerException expected) {
    }
  }

  public void testToMapWithNullValues() {
    Iterable<String> strings = ImmutableList.of("one", "two", "three");
    try {
      Maps.toMap(strings, Functions.constant(null));
      fail();

    try {
      Maps.toMap((Iterable<String>) strings, Functions.constant("foo"));
      fail();
    } catch (NullPointerException expected) {
    }
  }

  public void testToMapWithNullValues() {
    Iterable<String> strings = ImmutableList.of("one", "two", "three");
    try {
      Maps.toMap(strings, Functions.constant(null));
      fail();

   * IllegalArgumentException} is thrown when the collection operation is performed. (This differs
   * from the {@code Collector} returned by {@link Collectors#toMap(Function, Function)}, which
   * throws an {@code IllegalStateException}.)
   *
   * @since 21.0
   */
  public static <T extends @Nullable Object, K, V>