計算兩個日期之間的天數

package test;

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Calendar;

public class TestDifferentDay {

	/**date2比date1多的天數  
	 * @param date1  
	 * @param date2  
	 * @return 
	 * */
	public static int differentDays(Date date1, Date date2) {
		Calendar cal1 = Calendar.getInstance();
		cal1.setTime(date1);
		Calendar cal2 = Calendar.getInstance();
		cal2.setTime(date2);
		int day1 = cal1.get(Calendar.DAY_OF_YEAR);
		int day2 = cal2.get(Calendar.DAY_OF_YEAR);
		int year1 = cal1.get(Calendar.YEAR);
		int year2 = cal2.get(Calendar.YEAR);
		if (year1 != year2) { // 同一年
			int timeDistance = 0;
			for (int i = year1; i < year2; i++) {
				if (i % 4 == 0 && i % 100 != 0 || i % 400 == 0) { // 閏年
					timeDistance += 366;
				} else { // 不是閏年
					timeDistance += 365;
				}
			}
			return timeDistance + (day2 - day1);
		} else { // 不一樣年
			System.out.println("判斷day2 - day1 : " + (day2 - day1));
			return day2 - day1;
		}
	}

	/**
	 * 經過時間秒毫秒數判斷兩個時間的間隔
	 * 
	 * @param date1
	 * @param date2
	 * @return
	 * */
	public static int differentDaysByMillisecond(Date date1, Date date2) {
		int days = (int) ((date2.getTime() - date1.getTime()) / (1000 * 3600 * 24));
		return days;
	}

	public static void main(String[] args) {

		String dateStr = "2008-1-1 1:21:28";
		String dateStr2 = "2010-1-2 1:21:28";
		SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
		SimpleDateFormat format2 = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
		try {
			Date date2 = format.parse(dateStr2);
			Date date = format.parse(dateStr);
			System.out.println("兩個日期的差距：" + differentDays(date, date2));
			System.out.println("兩個日期的差距：" + differentDaysByMillisecond(date, date2));
		} catch (ParseException e) {
			e.printStackTrace();
		}
	}
}