java计算两个日期之间相差的天数

/**
*日期格式的计算
*/ 
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));    
    }