根据输入日期，获得当前月的天数

int year=0;
        int month=0;
        Calendar startDay = Calendar.getInstance();
        String[] date=null;
        try{
            startDay.setTime(FORMATTER.parse(beginTime));
            year=startDay.get(Calendar.YEAR);
            month=startDay.get(Calendar.MONTH);
            startDay.set(Calendar.YEAR, year);
            startDay.set(Calendar.MONTH, month);
            startDay.set(Calendar.DATE, 1);//把日期设置为当月第一天
            startDay.roll(Calendar.DATE, -1);//日期回滚一天，也就是最后一天
            int maxDate = startDay.get(Calendar.DATE);
            date=new String[maxDate];
            for (int i = 0; i < maxDate; i++){
                date[i]=(i+1)+"";
            }
        }catch (ParseException e){
            e.printStackTrace();
        }