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("2013-04-21 20:00:10");
		Date d2=sdf.parse("2013-07-10 14:54:00");
		System.out.println(daysBetween(d1,d2));

		System.out.println(daysBetween("2013-04-21 20:00:10","2013-07-10 14:54:00")+1);
	}

	/**
     * 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));
    }

}