private static  Date getDateAdd(int days){
    SimpleDateFormat sf = new SimpleDateFormat("yyyy-MM-dd");
    Calendar c = Calendar.getInstance();
    c.add(Calendar.DAY_OF_MONTH, -days);
   return c.getTime();
}
private static  List<String> getDaysBetwwen(int days){ //最近几天日期
    List<String> dayss = new ArrayList<>();
    Calendar start = Calendar.getInstance();
    start.setTime(getDateAdd(days));
    Long startTIme = start.getTimeInMillis();
    Calendar end = Calendar.getInstance();
    end.setTime(new Date());
    Long endTime = end.getTimeInMillis();
    Long oneDay = 1000 * 60 * 60 * 24l;
    Long time = startTIme;
    while (time <= endTime) {
        Date d = new Date(time);
        DateFormat df = new SimpleDateFormat("yyyy-MM-dd");
        System.out.println(df.format(d));
        dayss.add(df.format(d));
        time += oneDay;
    }
    return dayss;
}