计算日期的天数差

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;
public class test16 {
/**
@param args
@throws ParseException
*/
public static void main(String[] args) throws ParseException {
// TODO Auto-generated method st
SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
Date d1=sdf.parse("2012-09-08 10:10:10");
Date d2=sdf.parse("2012-09-15 00:00:00");
System.out.println(daysBetween(d1,d2));
System.out.println(daysBetween("2012-09-08 10:10:10","2012-09-15 00:00:00"));  
}
/**
计算两个日期之间相差的天数
@param smdate 较小的时间
@param bdate 较大的时间
@return 相差天数
@throws ParseException
/
public static int daysBetween(Date smdate,Date bdate) throws ParseException
{
SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd");
smdate=sdf.parse(sdf.format(smdate));
bdate=sdf.parse(sdf.format(bdate));
Calendar cal = Calendar.getInstance();
cal.setTime(smdate);
long time1 = cal.getTimeInMillis();
cal.setTime(bdate);
long time2 = cal.getTimeInMillis();
long between_days=(time2-time1)/(10003600*24);
return Integer.parseInt(String.valueOf(between_days));
}
/*
字符串的日期格式的计算
/
public static int daysBetween(String smdate,String bdate) throws ParseException{
SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd");
Calendar cal = Calendar.getInstance();
cal.setTime(sdf.parse(smdate));
long time1 = cal.getTimeInMillis();
cal.setTime(sdf.parse(bdate));
long time2 = cal.getTimeInMillis();
long between_days=(time2-time1)/(10003600*24);
   return Integer.parseInt(String.valueOf(between_days));     
}  
}
// 转为毫秒相除