Iterator<Integer> result =
        Iterators.transform(
            input,
            new Function<String, Integer>() {
              @Override
              public Integer apply(String from) {
                return Integer.valueOf(from);
              }
            });

    List<Integer> actual = Lists.newArrayList(result);
    List<Integer> expected = asList(1, 2, 3);
    assertEquals(expected, actual);
  }