Java计算两个日期相差的天数

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 stub
        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)/(1000*3600*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)/(1000*3600*24);

       return Integer.parseInt(String.valueOf(between_days));
    }

}