//  实现给定某日期，判断是星期几  
     public static String getWeekday(String date){//必须yyyy-MM-dd  
        SimpleDateFormat sd = new SimpleDateFormat("yyyy-MM-dd");    
        SimpleDateFormat sdw = new SimpleDateFormat("E");    
        Date d = null;    
        try {    
            d = sd.parse(date);    
        } catch (ParseException e) {    
            e.printStackTrace();    
        }  
        return sdw.format(d);  
     }