java 时间Calendar

       // 当前时间对应的年、月、日、时、分、秒
       Calendar c = Calendar.getInstance();
       int year = c.get(Calendar.YEAR);
       int month = c.get(Calendar.MONTH) + 1;// 0-11 从一月到12月
       int day = c.get(Calendar.DATE);
       int week = c.get(Calendar.DAY_OF_WEEK); //1-7 从周日到周一
       int weekYear = c.get(Calendar.WEEK_OF_YEAR); // 一年的第几周
       long timeInMillis = c.getTimeInMillis();
       // 元旦零点
       Calendar newYearDayStart = Calendar.getInstance();
       newYearDayStart.set(Calendar.YEAR, Calendar.JANUARY, 1, 0, 0, 0);
       // 元旦23时59分59秒
       Calendar newYearDayEnd = Calendar.getInstance();
       newYearDayEnd.set(Calendar.YEAR, Calendar.JANUARY, 1, 23, 59, 59);
       // 当月第一天的零点
       Calendar monthDayFirstStart = Calendar.getInstance();
       monthDayFirstStart.set(Calendar.YEAR, Calendar.MONTH, 1, 0, 0, 0);
       // 当月第一天的23时59分59秒
       Calendar monthDayFirstEnd = Calendar.getInstance();
       monthDayFirstEnd.set(Calendar.YEAR, Calendar.MONTH, 1, 23, 59, 59);

        Calendar yesterdayStart = Calendar.getInstance();
        yesterdayStart.set(year, Calendar.MONTH, day - 1, 0, 0, 0);//昨天零时零分零秒
        Calendar yesterdayEnd = Calendar.getInstance();
        yesterdayEnd.set(year, Calendar.MONTH, day - 1, 23, 59, 59);// 昨天的23时59分59秒

         Calendar calendar = Calendar.getInstance();
         calendar.set(calendar.get(Calendar.YEAR), calendar.get(Calendar.MONTH), calendar.get(Calendar.DAY_OF_MONTH), 0, 0, 0);
         calendar.set(Calendar.DAY_OF_WEEK, Calendar.MONDAY);
         calendar.add(Calendar.DAY_OF_WEEK, -7);//上周第一天
         calendar.set(calendar.get(Calendar.YEAR), calendar.get(Calendar.MONTH), calendar.get(Calendar.DAY_OF_MONTH), 23, 59, 59);
         calendar.add(Calendar.DAY_OF_WEEK, 6);// 上周最后一天