獲取兩個日期之間的間隔天數

	/**
	 * 獲取兩個日期之間的間隔天數（第二個日期必須大於第一個日期）
	 * @param t1 第一個時間 yyy-MM-dd
	 * @param t2 第二個時間 yyyy-MM-dd
	 * @return int 間隔天數
	 * @throws Exception
	 */
	private int getBetweenDays(String t1, String t2) throws Exception {
		SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");
		int betweenDays = 0;
		Date d1 = format.parse(t1);
		Date d2 = format.parse(t2);
		Calendar c1 = Calendar.getInstance();
		Calendar c2 = Calendar.getInstance();
		c1.setTime(d1);
		c2.setTime(d2);
		// 保證第二個時間一定大於第一個時間
		if (c1.after(c2)) {
			c1 = c2;
			c2.setTime(d1);
		}
		int betweenYears = c2.get(Calendar.YEAR) - c1.get(Calendar.YEAR);
		betweenDays = c2.get(Calendar.DAY_OF_YEAR)
				- c1.get(Calendar.DAY_OF_YEAR);
		for (int i = 0; i < betweenYears; i++) {
			c1.set(Calendar.YEAR, (c1.get(Calendar.YEAR) + 1));
			betweenDays += c1.getMaximum(Calendar.DAY_OF_YEAR);
		}
		return betweenDays;
	}