Visit all nodes from DOM

 
import java.io.File;

import javax.xml.parsers.DocumentBuilderFactory;

import org.w3c.dom.Document;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;

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"));

    visit(doc, 0);
  }
  public static void visit(Node node, int level) {
    NodeList list = node.getChildNodes();
    for (int i = 0; i < list.getLength(); i++) {
      Node childNode = list.item(i);
      visit(childNode, level + 1);
    }
  }
}