private void fetchBuyingAndSellingRate(String line, String currency) throws ParserConfigurationException, SAXException, IOException {
        if (line == null) {
            return;
        }
        String URL_SOURCE = "http://www.nbp.pl/kursy/xml/" + line + ".xml";
        Document doc = dataFetcher.getXML(URL_SOURCE);
        NodeList nList = doc.getElementsByTagName("pozycja");

        for (int temp = 0; temp < nList.getLength(); temp++) {
            Node nNode = nList.item(temp);

            if (nNode.getNodeType() == Node.ELEMENT_NODE) {
                Element eElement = (Element) nNode;
                if (eElement.getElementsByTagName(CURRENCY_CODE).item(0).getTextContent().equals(currency)) {
                    buyingRate = getFieldFromDOM(eElement, BUY_RATE_TAG);
                    sellingRate = getFieldFromDOM(eElement, SELL_RATE_TAG);
                }
            }
        }
        sumOfBuyingRate += buyingRate;
        sellingRates.add(sellingRate);
    }