Collections.sort(messages, new Comparator() {
                                @Override
                                public int compare(Object o1, Object o2) {
                                    Message p1 = (Message) o1;
                                    Message p2 = (Message) o2;
                                    if (p1.getCreatedAt().compareTo(p2.getCreatedAt()) > 0) {
                                        return -1;
                                    } else if (p1.getCreatedAt().compareTo(p2.getCreatedAt()) < 0) {
                                        return +1;
                                    } else {
                                        return 0;
                                    }

                                }
                            });