Calendar获得某一月份天数

static int getLenOfMonth(Calendar Cal){
	if(Cal.get(Cal.MONTH)>=0&&Cal.get(Cal.MONTH)<12)
	{
		Cal.set(Cal.DATE, 1);
		Cal.roll(Cal.DATE, -1);
		return (int)Cal.get(Cal.DATE);
	}
	else
	return 0;
}