得到几天前，几天后的时间

    /**
       * 得到几天前的时间
       * @param d
       * @param day
       * @return
       */ 
      public static Date getDateBefore(Date d,int day){ 
       Calendar now =Calendar.getInstance(); 
       now.setTime(d); 
       now.set(Calendar.DATE,now.get(Calendar.DATE)-day); 
       return now.getTime(); 
      } 
      
      /**
       * 得到几天后的时间
       * @param d
       * @param day
       * @return
      */ 
      public static Date getDateAfter(Date d,int day){ 
       Calendar now =Calendar.getInstance(); 
       now.setTime(d); 
       now.set(Calendar.DATE,now.get(Calendar.DATE)+day); 
       return now.getTime(); 
     }