java获取日期之间天数的方法

private int daysBetween(Date now, Date returnDate) {  Calendar cNow = Calendar.getInstance();  Calendar cReturnDate = Calendar.getInstance();  cNow.setTime(now);  cReturnDate.setTime(returnDate);  setTimeToMidnight(cNow);  setTimeToMidnight(cReturnDate);  long todayMs = cNow.getTimeInMillis();  long returnMs = cReturnDate.getTimeInMillis();  long intervalMs = todayMs - returnMs;  return millisecondsToDays(intervalMs);}private int millisecondsToDays(long intervalMs) {  return (int) (intervalMs / (1000 * 86400));}private void setTimeToMidnight(Calendar calendar) {  calendar.set(Calendar.HOUR_OF_DAY, 0);  calendar.set(Calendar.MINUTE, 0);  calendar.set(Calendar.SECOND, 0);}