java计算两个日期之间相隔的天数

　　

 import java.text.ParseException;
 import java.text.SimpleDateFormat;
 import java.util.Calendar;
 import java.util.Date;

 public class date {

     /**
      * @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));
     }

 }