java 计算2个日期差的天数

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));  
    }

}