SAXBuilder saxBuilder = new SAXBuilder(); 
\\where modelPath a string originated from the IPath of the  model file
Document originalDoc = saxBuilder.build(new File(modelPath));

\\an outputter with a pretty print format
XMLOutputter xmlOutput = new XMLOutputter();
xmlOutput.setFormat(Format.getPrettyFormat());	
\\the new doc that you will write too
Document exportDoc = new Document();
.....
.....your processing methods
.....
\\xmlOutputter can be used to write the xml to the file, you will need to call the .output method with the exported doc and an OutputStreamWriter

public static List<Element> getElements(String regex, Document doc, Namespace ns) {
    	XPathFactory xFactory = XPathFactory.instance();
        XPathExpression<Element> expr = xFactory.compile(regex, Filters.element(), null, ns);    
        return expr.evaluate(doc);   
 }


\\a sample caller of the method
getElements("//elementName",doc,namespace).
			forEach(el->{
                             //do your processing with lamdas
                             // e.g Element myElement = new Element("test");
                             // etc
                        });