class BithumbUtils {

  private BithumbUtils() {
    // not called
  }

  public static String getBaseCurrency(@Nullable CurrencyPair currencyPair) {
    return Optional.ofNullable(currencyPair)
        .map(c -> c.base)
        .map(Currency::getCurrencyCode)
        .orElse(null);
  }

  public static String getCounterCurrency() {
    return Currency.KRW.getCurrencyCode();
  }

  public static String fromOrderType(Order.OrderType type) {<FILL_FUNCTION_BODY>}
}

    switch (type) {
      case BID:
        return "bid";
      case ASK:
        return "ask";
      default:
        throw new NotAvailableFromExchangeException();
    }
  
<no_super_class>