JAVA Xpath expression to return null when attribute not found

In the following xml sample

      <employee>
        <payment contractType="1">
          <income type="0">
            <gr amount="2063.00" kae="211" code="1" />
            <gr amount="400.00" kae="215" code="6" />
            <et amount="47.55" kae="292" code="4012501" />
            <et amount="105.21" kae="293" code="4052000" />
            <de amount="88.15" code="4003101" />
          </income>
         </payment>
      </employee>
      <employee>
        <payment contractType="1">
          <income type="0">
            <gr amount="70.00" kae="213" code="4" />
            <gr amount="1560.00" kae="211" code="1" />
          </income>
       </payment>
    </employee>

i need to get the value of "amount" for "code" = "4". If the income node does not contain such data ( gr with code = "4") i need to return something like null or boolean false. Purpose is to look through all the employees in the xml file, load them on an Arraylist with 0 if they dont have any amount with code 4 else load the amount value.

code i use for this part :

    public class ReadXMLfile {
    public static void main(String[] args) {

    try {
        FileInputStream file = new FileInputStream(new File("E2015_1_1.xml"));

        DocumentBuilderFactory builderFactory = DocumentBuilderFactory.newInstance();

        DocumentBuilder builder =  builderFactory.newDocumentBuilder();

        Document xmlDocument = builder.parse(file);

        XPath xPath =  XPathFactory.newInstance().newXPath();


    expression = "/psp/body/organizations/organization/employees/employee/payment/income[@type='0']/gr";
    nodeList = (NodeList) xPath.compile(expression).evaluate(xmlDocument, XPathConstants.NODESET);
    ArrayList<String> gr4incomeList = new ArrayList<String>();

    for (int i = 0; i < nodeList.getLength(); i++) {

          String acode = (String)nodeList.item(i).getAttributes().getNamedItem("code").getNodeValue();
          System.out.println("acode = '" + acode + "'");

               if (acode.equals("4")){
                    System.out.println(nodeList.item(i).getAttributes().getNamedItem("amount").getNodeValue());
                    gr4incomeList.add(nodeList.item(i).getAttributes().getNamedItem("amount").getNodeValue());
                    System.out.println("array = " + gr4incomeList.get(i));
        }else
                    gr4incomeList.add("0000");

    }

     } catch (FileNotFoundException e) {
        e.printStackTrace();
    } catch (SAXException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    } catch (ParserConfigurationException e) {
        e.printStackTrace();
    } catch (XPathExpressionException e) {
        e.printStackTrace();
    }
}

}

Problem is it writes "0000" in the arraylist for any gr found except the ones with code = "4".

I am really stuck.

Any ideas? Thank you guys!