class BittrexUtils {

  public static final String MARKET_NAME_SEPARATOR = "-";

  public static String toPairString(Instrument currencyPair) {
    if (currencyPair == null) return null;
    return currencyPair.getBase().getCurrencyCode().toUpperCase()
        + MARKET_NAME_SEPARATOR
        + currencyPair.getCounter().getCurrencyCode().toUpperCase();
  }

  public static CurrencyPair toCurrencyPair(String pairString) {<FILL_FUNCTION_BODY>}

  /** Utility class */
  private BittrexUtils() {
    throw new AssertionError();
  }
}

    if (pairString == null) return null;
    String[] pairStringSplit = pairString.split(MARKET_NAME_SEPARATOR);
    if (pairStringSplit.length != 2) return null;
    return new CurrencyPair(pairStringSplit[0], pairStringSplit[1]);
  
<no_super_class>