得到几个月之内的天数（大家看看有没有更好的方法）

/**  
 * 得到指定月的天数  
 * */  
public static int getMonthLastDay(int year, int month)   
{   
    Calendar a = Calendar.getInstance();   
    a.set(Calendar.YEAR, year);   
    a.set(Calendar.MONTH, month - 1);   
    a.set(Calendar.DATE, 1);//把日期设置为当月第一天   
    a.roll(Calendar.DATE, -1);//日期回滚一天，也就是最后一天   
    int maxDate = a.get(Calendar.DATE);   
    return maxDate;   
}  

	
public static int getSameMonthDay(int year, int startYear, int month, int startMonth, int i){
	int threeMonthDay = 0;
	if(startMonth<i){
		if(month==0){
			month += 12;
			year=year-1;
		}
		if(month>0&&(year==startYear)){
			threeMonthDay += getSameMonthDay(year, startYear, month-1, startMonth, i);
		}else if(12-i+startMonth<=month){
			threeMonthDay += getSameMonthDay(year, startYear, month-1, startMonth, i);
		}
	}else{
		if(startMonth-i<=month){
			threeMonthDay += getSameMonthDay(year, startYear, month-1, startMonth, i);
		}
	}
	threeMonthDay += getMonthLastDay(year, month);
	return threeMonthDay;
}