java将两个日期相减得到天数

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Calendar;
public class dateCov {
public static void main(String[] args) {
System.out.println("相差日期为：" + dateCov.daysxiangcha("2010-10-20", "2010-12-20"));
}
public static int daysxiangcha(String dateStr1, String dateStr2) {
SimpleDateFormat sdf = new SimpleDateFormat("yyyyMMdd");
SimpleDateFormat sdf2 = new SimpleDateFormat("yyyy-MM-dd");
try {
dateStr1 = sdf.format(sdf2.parse(dateStr1));
dateStr2 = sdf.format(sdf2.parse(dateStr2));
} catch (ParseException e) {
e.printStackTrace();
}
int year1 = Integer.parseInt(dateStr1.substring(0, 4));
int month1 = Integer.parseInt(dateStr1.substring(4, 6));
int day1 = Integer.parseInt(dateStr1.substring(6, 8));
int year2 = Integer.parseInt(dateStr2.substring(0, 4));
int month2 = Integer.parseInt(dateStr2.substring(4, 6));
int day2 = Integer.parseInt(dateStr2.substring(6, 8));
Calendar c1 = Calendar.getInstance();
c1.set(Calendar.YEAR, year1);
c1.set(Calendar.MONTH, month1 - 1);
c1.set(Calendar.DAY_OF_MONTH, day1);
Calendar c2 = Calendar.getInstance();
c2.set(Calendar.YEAR, year2);
c2.set(Calendar.MONTH, month2 - 1);
c2.set(Calendar.DAY_OF_MONTH, day2);
long mills =
c1.getTimeInMillis() > c2.getTimeInMillis()
? c1.getTimeInMillis() - c2.getTimeInMillis()
: c2.getTimeInMillis() - c1.getTimeInMillis();
return (int) (mills / 1000 / 3600 / 24);
}
}