Java获取N天前，N天后的日期（如3天）

    /**
     *
     * @param num ﹣3 三天前 +3 三天后
     * @return
     */
    public static String getDayAgoOrAfterString(int num){
        Calendar calendar1 = Calendar.getInstance();
        SimpleDateFormat sdf1 = new SimpleDateFormat("yyyy-MM-dd");
        calendar1.add(Calendar.DATE, num);
/*
        Calendar calendar1 = Calendar.getInstance();
        calendar1.set(Calendar.SECOND, 59);
        calendar1.set(Calendar.MINUTE, 59);
        calendar1.set(Calendar.HOUR_OF_DAY, 23);
        calendar1.set(Calendar.MILLISECOND, 999);
        SimpleDateFormat sdf1 = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        calendar1.add(Calendar.DATE, num);
*/
        return sdf1.format(calendar1.getTime());
    }