Java Calendar 计算两个时间相隔天数

import java.text.ParseException;  
import java.text.SimpleDateFormat;  
import java.util.Calendar;  
import java.util.Date;
/**
 * @author Saffi
 * @date 2017-10-25
 */  
public class testDays {
     /**
     * @param args
     * @throws ParseException  
     */  
    public static void main(String[] args) throws ParseException {  
        //定义时间格式年月日 时分秒
        SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");  
        Date d1=sdf.parse("2014-09-15 00:00:00");  
        Date d2=sdf.parse("2017-10-25 00:00:00");
        //方法一：日期格式的计算   
        System.out.println(daysBetween(d1,d2));  
        //方法二：字符串的日期格式的计算
        System.out.println(daysBetween("2014-09-15 00:00:00","2017-10-25 00:00:00"));  
    }  
      
    /**  
     * 日期格式的计算   
     * @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
     * @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(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));     
    }  
 
}