list 集合排序

 Collections.sort(messageList, new Comparator<MSMessage>() {
                @Override
                public int compare(MSMessage msMessage1, MSMessage msMessage2) {
                    long diff = msMessage1.getDate() - msMessage2.getDate();
                    if (diff > 0) {
                        return 1;
                    } else if (diff < 0) {
                        return -1;
                    }
                    return 0;
                }
            });