ArrayList按照时间排序，ArrayList时间排序

ArrayList按照时间排序，ArrayList时间排序

Collections.sort(relationUserList, new Comparator<RelationUser>() {
    @Override
    public int compare(RelationUser relationUser1, RelationUser relationUser2) {
        return (relationUser2.getLastMessagecreateAt() + "").compareTo(relationUser1.getLastMessagecreateAt() + "");
    }
});