java 日期计算

梦里梦外; 2021-11-04 17:28 473阅读 0赞

java 日期相关计算获取

public static void main(String[] args) {
       Date date = new Date();
       String dateStr = "2019-01-07";
       SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
       try {
          date = sdf.parse(dateStr);
       } catch (ParseException e) {
          e.printStackTrace();
       }
    
       //获取月份中的第一天
       Calendar cdMin = Calendar.getInstance();
       cdMin.setTime(date);
       cdMin.set(Calendar.DAY_OF_MONTH,cdMin.getActualMinimum(Calendar.DAY_OF_MONTH));
       String monthLast = sdf.format(cdMin.getTime());
       System.out.println("这个月的第一天:"+monthLast);
    
       //获取月份中的最后一天
       Calendar cd = Calendar.getInstance();
       cd.setTime(date);
       cd.set(Calendar.DAY_OF_MONTH,cd.getActualMaximum(Calendar.DAY_OF_MONTH));
       String monthLastDate = sdf.format(cd.getTime());
       System.out.println("这个月的最后一天:"+monthLastDate);
    
       //获取这个日期年所在的天数
       Calendar calendar = Calendar.getInstance();
       calendar.setTime(date);
       int week = calendar.get(Calendar.DAY_OF_WEEK);
       //如果是周天的话就要减去一天，不然就会跳到下周一
       if(1== week){
          calendar.add(Calendar.DAY_OF_MONTH, -1);
       }
       calendar.setFirstDayOfWeek(Calendar.MONDAY);
       int week1 = calendar.get(Calendar.DAY_OF_WEEK);
       calendar.add(Calendar.DATE,calendar.getFirstDayOfWeek()- week1);
       String weekStr = sdf.format(calendar.getTime());
       System.out.println("这个日期是一周中的第："+week1+"天");
       System.out.println("这个日期所在的周一是："+weekStr);
    
       //在这个日期加一天
       Calendar calendarAdd = Calendar.getInstance();
       calendarAdd.setTime(date);
       calendarAdd.add(Calendar.DAY_OF_WEEK,1);
       String dateAddOne = sdf.format(calendarAdd.getTime());
       System.out.println("当前时间是："+dateStr+",加一天后是："+dateAddOne);
    
       //这个日期减一天
       Calendar calendarCutOne = Calendar.getInstance();
       calendarCutOne.setTime(date);
       calendarCutOne.add(Calendar.DAY_OF_MONTH,-1);
       String dateCutOne = sdf.format(calendarCutOne.getTime());
       System.out.println("当前时间是："+dateStr+",减一天后是："+dateCutOne);
    
       //这个日期在年中的周数
       Calendar calendarWeek = Calendar.getInstance();
       calendarWeek.setTime(date);
       int year = calendarWeek.getWeekYear();
       //先设置周一为周的第一天
       int firstWeek = calendarWeek.get(Calendar.MONDAY);
       if(1 == firstWeek){
          calendarWeek.add(Calendar.DAY_OF_MONTH,-1);
       }
       calendarWeek.setFirstDayOfWeek(Calendar.MONDAY);
       int yearWeek = calendarWeek.get(Calendar.WEEK_OF_YEAR);
       System.out.println("当前年为："+year +"，这个日期所在年的第"+yearWeek+"周");
    }