public String getExitGreeting(String hour) {
        int time = Integer.parseInt(hour);
        if (time >= 0  && time < 12) {
            return GOODBYE_MORNING;
        } else if (time >=12 && time < 17) {
            return GOODBYE_AFTERNOON;
        } else if (time >=17 && time < 19) {
            return GOODBYE_EVENING;
        } else if (time >= 20 && time < 24) {       
            return GOODBYE_NIGHT;
        } else {
            return "";
        }
    }