Java 8 Method Reference - Method Reference on Instance Examples

public class ObjectRefExample {

    DataService dataService = new DataService();

    public static void main(String[] args) {

        ObjectRefExample example = new ObjectRefExample();
        example.showUsersInfo();
    }

    private void showUsersInfo() {
        List<String> userIds = dataService.getAllUserIds();
        //method ref on instance, using this
        userIds.forEach(this::displayUserInfo);
    }

    private void displayUserInfo(String id) {
        System.out.println("User Info for id :" + id);
        //method ref on dataService instance
        display(id, dataService::getUserNameById);
        display(id, dataService::getUserAddressById);
        System.out.println("------------------------");
    }

    private void display(String id, Function<String, ?> theConsumer) {
        System.out.println(theConsumer.apply(id));
    }
}

    @PostConstruct
    private void postConstruct () {
        Stream.iterate(1L, a -> a + 1)
              .limit(10)
              .forEach(this::createCustomer);
    }

    private void createCustomer (Long id) {
        DataFactory df = new DataFactory();
        Customer c = new Customer();
        c.setName(df.getName());
        c.setId(id);
        Address a = new Address();
        a.setStreet(df.getNumberText(4)+" "+df.getStreetName());
        a.setCity(df.getCity());
        a.setCounty(df.getItem(Locale.getISOCountries()));
        a.setZipCode(df.getNumberText(5));
        c.setAddress(a);
        customerMap.put(c.getId(), c);
    }