日期与字符串间的相互转化

public class DateUtil {

   private static  SimpleDateFormat sdf;


         public static String   dateToStr(Date date, String pattern){
              sdf=new SimpleDateFormat(pattern);
             return sdf.format(date);
         }

        public static Date   strToDate(String dateStr, String pattern){
             sdf=new SimpleDateFormat(pattern);
            try {
                return sdf.parse(dateStr);
            } catch (ParseException e) {
                e.printStackTrace();
                return null;
            }
        }
}