java 时间处理 获取周的第一天 最后一天，月的第一天和最后一天：

Calendar calendar=Calendar.getInstance(); calendar.setTime(new Date()); //设置当前时间SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd");SimpleDateFormat sdfall=new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");//获取天开始时间和结束时间startDate=sdf.parse(sdf.format(calendar.getTime()));endDate=sdfall.parse(sdf.format(calendar.getTime())+" 23:59:59");//获取当前周的一天后最后一天calendar.setFirstDayOfWeek(Calendar.MONDAY);calendar.set(Calendar.DAY_OF_WEEK,calendar.getFirstDayOfWeek()); startDate=sdf.parse(sdf.format(calendar.getTime()));calendar.set(Calendar.DAY_OF_WEEK,calendar.getFirstDayOfWeek()+6); endDate=sdfall.parse(sdf.format(calendar.getTime())+" 23:59:59");//获取当前月的第一天和最后一天calendar.set(calendar.get(Calendar.YEAR),calendar.get(Calendar.MONTH), 1);startDate=sdf.parse(sdf.format(calendar.getTime()));calendar.roll(Calendar.DATE, -1);endDate=sdfall.parse(sdf.format(calendar.getTime())+" 23:59:59");