Java 8 Optional

public class OptionalTest {

    private User getUser() {
        return null;
    }

    @Test
    public void test1() {

        User user = getUser();

        String city = "未知";

        if (user!=null) {
            Address address = user.getAddress();
            if (address!=null) {
                city = address.getCity();
            }
        }

    }

    @Test
    public void test2() {
        Optional<User> optionalUser = Optional.ofNullable(getUser());

        String city = optionalUser
                .map(User::getAddress)
                .map(Address::getCity)
                .orElse("未知");

    }

}