求时间的格式与星期几

Question

2021年5月28日是星期五。现在从2021年5月28日零点开始计时，根据给定的计时毫秒数，求计时时刻的时间格式，并输出当时是星期几（其中星期日输出7）。 样例输入 86400001 样例输出 00:00:00 6 数据范围 n<1e16

Answer 1

public static void main(String[] args){
    System.out.println(getTime(86400001L));
}

private static String getTime(Long time){
    try{
        SimpleDateFormat sdf1 = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        String fromDate = "2021-05-28 00:00:00";
        //计算2021-05-28 00:00:00 的时间戳
        long fromLong = sdf1.parse(fromDate).getTime();
        //加上time，算目标时间的时间戳
        long resLong = fromLong + time;
        //转换成date
        Date date = new Date(resLong);

        //是几点
        SimpleDateFormat sdf2 = new SimpleDateFormat("HH:mm:ss");
        String clock = sdf2.format(date);
        //是星期几
        int week = getWeek(date);
        return clock + " " + week;
    }catch (Exception e){
        e.printStackTrace();
        return "";
    }
}

public static int getWeek(Date date){
    Calendar cal = Calendar.getInstance();
    cal.setTime(date);
    int week_index = cal.get(Calendar.DAY_OF_WEEK) - 1;
    if(week_index<0){
        week_index = 7;
    }
    return week_index;
}