How to order cities name by their letters, not plate code in the list?

Question

This is written in Java. It works perfectly. But it writes cities based on their plate code from 1 to 80 for example. But city names for example 1- ZCity, 2-ACity, so it is not what I want.

What should I change in this code to produce cities by their name(letters)

Here is the code:

@RequestMapping(value = "/getCities", method = RequestMethod.GET)
    @Cacheable("cities")
    public @ResponseBody List<KeyValueDTO> getCities() {
        logger.trace("getCities begins.");
        List<City> cityList = cityService.findAll();
        List<KeyValueDTO> cityKeyDtoList = new ArrayList<>();
        for (City city : cityList) {
            KeyValueDTO cityKeyDto = new KeyValueDTO();
            cityKeyDto.setKey(city.getName());
            cityKeyDto.setValue(String.valueOf(city.getCode()));
            cityKeyDtoList.add(cityKeyDto);
        }
        logger.trace("CityController: getAllCities ends");
        return cityKeyDtoList;
    }