Java Xpath A location step was expected following the ‘/’ or ‘//’ token

I try to get child of all parent node in my dictionnary but when I tried to get child of each parent I have this error :

A location step was expected following the "" or '//' token.

Java file :

Map<String, String> data = new HashMap<String, String>();
        XPath xpath = XPathFactory.newInstance().newXPath();
        NodeList nodesClasses = (NodeList) xpath.evaluate("/DVD/animation/node()", document, XPathConstants.NODESET);

        for (int i = 0; i < nodesClasses.getLength(); i++) {
            NodeList nodesDetails = (NodeList) xpath.evaluate("/DVD/animation/"+nodesClasses.item(i).getNodeName() + "/node()", document, XPathConstants.NODESET);
            for (int j = 0; j < nodesDetails.getLength(); j++) {
                data.put(nodesClasses.item(i).getNodeName(), nodesDetails.item(j).getNodeName());