Replacing XML in a file from "Document" in Java

after processing my first steps in working with XML in java. I am now at the point where I want to update some data in the XML / GPX file ...

Reusing it in my "Document" works great :)

The question arises: how can I save the modified "document" -model back to my file? Should I be doing this using standard file functions (via pairs, etc.) and another more elegant way to do it ?; -)

Here is the code I have already worked out, maybe it can help. (the getParsedXML method just transfers the conversion from the file to an additional method)

                Document tmpDoc = getParsedXML(currentGPX);

            //XML Parsind tests:
            // Access to tag attribute <tag attribut="bla">
            System.out.println(tmpDoc.getElementsByTagName("wpt").item(0).getAttributes().getNamedItem("lat").getTextContent());

            // Access to the value of an child element <a><CHILD>ValueOfChild</CHILD></a>
            System.out.println(tmpDoc.getElementsByTagName("wpt").item(0).getChildNodes().item(5).getTextContent());

            // Replacing access to tag attribute
            tmpDoc.getElementsByTagName("wpt").item(0).getAttributes().getNamedItem("lat").setTextContent("139.921055008");
            System.out.println(tmpDoc.getElementsByTagName("wpt").item(0).getAttributes().getNamedItem("lat").getTextContent());

            // Replacing access to child element value
            tmpDoc.getElementsByTagName("wpt").item(0).getChildNodes().item(5).setTextContent("Cala Sant Vicenç - Mallorca 2");
            System.out.println(tmpDoc.getElementsByTagName("wpt").item(0).getChildNodes().item(5).getTextContent());