（版本1）
publicstaticint getIntervalDays(Date fDate, Date oDate) {
if (null == fDate || null == oDate) {
return -1;
}
long intervalMilli = oDate.getTime() - fDate.getTime();
return (int) (intervalMilli / (24 * 60 * 60 * 1000));
}
（版本2）
publicstaticint daysOfTwo(Date fDate, Date oDate) {
Calendar aCalendar = Calendar.getInstance();
aCalendar.setTime(fDate);
int day1 = aCalendar.get(Calendar.DAY_OF_YEAR);
aCalendar.setTime(oDate);
int day2 = aCalendar.get(Calendar.DAY_OF_YEAR);
return day2 - day1;
}