import java.io.File;
import javax.xml.parsers.DocumentBuilderFactory;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.NodeList;
import org.w3c.dom.ProcessingInstruction;
public class Main {
public static void main(String[] argv) throws Exception {
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
factory.setValidating(true);
factory.setExpandEntityReferences(false);
Document doc = factory.newDocumentBuilder().parse(new File("filename"));
// Add a PI at the beginning of the document
Element element = doc.getDocumentElement();
ProcessingInstruction pi = doc.createProcessingInstruction("target", "instruction");
element.getParentNode().insertBefore(pi, element);
}
}