code: public double getExchangeRate(Currency otherCurrency) throws NoExchangeRate {
          return Common.getInstance().getStorageHandler().getStorageEngine().getExchangeRate(this, otherCurrency);
      }
docs: Returns the exchange rate between 2 currency.
  
  @param otherCurrency The other currency to exchange to
  @return The exchange rate or Double.MIN_VALUE if no exchange information are found.
  @throws com.greatmancode.craftconomy3.utils.NoExchangeRate If there's no exchange rate between the 2 currencies.