如何用java计算两个日期之间间隔多少天

Calendar now = Calendar.getInstance();
Calendar startTimeCal = Calendar.getInstance();
Calendar endTimeCal = Calendar.getInstance();
long buyCount;
startTimeCal.setTime(start_date);
endTimeCal.setTime(end_date);
if (endTimeCal.get(Calendar.YEAR) == startTimeCal.get(Calendar.YEAR)) {// 年份一致
buyCount =
endTimeCal.get(Calendar.DAY_OF_YEAR)
- startTimeCal.get(Calendar.DAY_OF_YEAR) + 1;
} else {// 年份不一致
buyCount =
now.getActualMaximum(Calendar.DAY_OF_YEAR)
- startTimeCal.get(Calendar.DAY_OF_YEAR)
+ endTimeCal.get(Calendar.DAY_OF_YEAR) + 1;
}
model.setBuyCount(buyCount);