两个日期相差的天数

Date dt=new Date();
SimpleDateFormat matter1=new SimpleDateFormat("yyyy-MM-dd");
System.out.println(matter1.format(dt));
String dateStr = "2017-11-27";
String dateStr2 = matter1.format(dt);
System.out.println("dateStr= "+dateStr);
System.out.println("dateStr2= "+dateStr2);
SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");
SimpleDateFormat format2 = new SimpleDateFormat("yyyy-MM-dd");

try
{
Date date = format.parse(dateStr);
Date date2 = format.parse(dateStr2);
int betweenDays=differentDays(date2,date);
System.out.println("两个日期的差距：" +betweenDays );
if (betweenDays<=7) {

}
// System.out.println("两个日期的差距：" + differentDaysByMillisecond(date,date2));
} catch (ParseException e) {
e.printStackTrace();
}

/**
* 通过时间秒毫秒数判断两个时间的间隔
* @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;
}

/**
* date2比date1多的天数
* @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) //闰年
{
timeDistance += 366;
}
else //不是闰年
{
timeDistance += 365;
}
}

return timeDistance + (day2-day1) ;
}
else //不同年
{
System.out.println("判断day2 - day1 : " + (day2-day1));
return day2-day1;
}
}