public class DateFormatter {
  /**
   * Date String 을 밀리세컨드로 변환
   * @param pattern yyyy-MM-dd
   * @param dateStr 2016-10-21
   * @return 밀리세컨드 
   */
  public static long dateStringToMillis(String pattern, String dateStr) {
    DateFormat format = new SimpleDateFormat(pattern);
    try {
      return format.parse(dateStr).getTime();
    } catch (ParseException e) {
      e.printStackTrace();
      return 0;
    }
  }
  
  
  /**
   * 날짜/시간 변환
   *
   * @param timeMillis 밀리세컨드
   * @param pattern    yyyy-MM-dd HH:mm:ss
   * @return 2016-10-21 09:01:03
   */
  public static String format(long timeMillis, String pattern) {
    return new SimpleDateFormat(pattern, Locale.getDefault()).format(timeMillis);
  }
} 
long time = DateFormatter.dateStringToMillis("H시 mm분", "10시 45분");
String timeStr = DateFormatter.format(time, "HH:mm"); // => 10:45, 09:45