return Integer.valueOf(from);
              }
            });

    result.next();
    assertThrows(NumberFormatException.class, () -> result.next());
  }

  public void testNullFriendlyTransform() {
    Iterator<@Nullable Integer> input = Arrays.<@Nullable Integer>asList(1, 2, null, 3).iterator();
    Iterator<String> result =
        Iterators.transform(
            input,