Java实现日期加减法privatestaticDateaddDay(Datedate,intdays){Calendarcalendar=Calendar.getInstance();日历.setTime(日期);calendar.add(Calendar.DATE,days);returncalendar.getTime();}Calendar.YEAR:YearCalendar.MONTH:MonthCalendar.DATE:DayCalendar.HOUR:HourCalendar.MINUTE:MinuteCalendar.SECOND:Second用法示例publicstaticvoidmain(String[]args){SimpleDateFormatsdf=newSimpleDateFormat("yyyy-MM-ddHH:mm:ss");日期date=newDate(1618459828000L);System.out.println(sdf.format(日期));日期=添加日期（日期，3）；系统。out.println(sdf.format(date));}output:2021-04-1512:10:282021-04-1812:10:28Java实现Date以保留日期部分privatestaticDategetDate(Datedate){日历calendar=Calendar.getInstance();日历.setTime(日期);//小时calendar.set(Calendar.HOUR_OF_DAY,0);//分钟calendar.set(Calendar.MINUTE,0);//第二个calendar.set(Calendar.SECOND,0);//毫秒calendar.set(Calendar.MILLISECOND,0);返回日历.getTime();}使用示例publicstaticvoidmain(String[]args){SimpleDateFormatsdf=newSimpleDateFormat("yyyy-MM-ddHH:mm:ss");日期date=newDate(1618459828000L);System.out.println(sdf.format(日期));日期=getDate(日期);System.out.println(sdf.format(date));}输出：2021-04-1512:10:282021-04-1500:00:00
