how to read few points from xml using java

I'm new to XML and I want to append points from an XML file to a point container that I wrote.

this is the XML file:

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<container>
    <point>
        <X>56</X>
        <Y>58</Y>
    </point>
    <point>
        <X>59</X>
        <Y>40</Y>
    </point>
    <point>
        <X>70</X>
        <Y>30</Y>
    </point>
</container>

this is what I did:

private void OpenFile () throws ParserConfigurationException, SAXException,       IOException {
    JFileChooser of = new JFileChooser();
    int option = of.showOpenDialog(of);
    while (!of.getSelectedFile().getName().endsWith(".xml")) {
        String error = "Error, Please select txt file";
        JOptionPane.showMessageDialog(this, error, "Wrong type of file", JOptionPane.INFORMATION_MESSAGE);
        of = new JFileChooser();
        option = of.showOpenDialog(of);
    }
    if (option == JFileChooser.APPROVE_OPTION){
        thisFile =  new File(of.getSelectedFile().getPath());
        DocumentBuilderFactory dbFactory = DocumentBuilderFactory.newInstance();
        DocumentBuilder dBuilder = dbFactory.newDocumentBuilder();
        Document doc = dBuilder.parse(thisFile);
        doc.getDocumentElement().normalize();

        NodeList nList = doc.getElementsByTagName("container");
        Element line = (Element) nList.item(0);
        for(int i =0 ; i < nList.getLength() ; i++) {
            Element point = (Element) line.getElementsByTagName("point").item(i);
            x = Integer.parseInt(point.getElementsByTagName("X").item(0).getTextContent());
            y = Integer.parseInt(point.getElementsByTagName("Y").item(0).getTextContent());
            drewPoints(x, y);
            pc.add(new Point(x, y));
        }
    }

my problem that it loop one time.