Java Most efficient method to iterate over all elements in a org w3c dom Document

Question

What is the most efficient way to iterate through all DOM elements in Java   Something like this but for every single DOM elements on current org w3c dom Document   for Node childNode   node getFirstChild    childNode  null        Node nextChild   childNode getNextSibling           Do something with childNode  including move or delete        childNode   nextChild

User · Answer

I also stumbled over this problem recently. Here is my solution. I wanted to avoid recursion, so I used a while loop.

Because of the adds and removes in arbitrary places on the list, I went with the LinkedList implementation.

/* traverses tree starting with given node */
  private static List<Node> traverse(Node n)
  {
    return traverse(Arrays.asList(n));
  }

  /* traverses tree starting with given nodes */
  private static List<Node> traverse(List<Node> nodes)
  {
    List<Node> open = new LinkedList<Node>(nodes);
    List<Node> visited = new LinkedList<Node>();

    ListIterator<Node> it = open.listIterator();
    while (it.hasNext() || it.hasPrevious())
    {
      Node unvisited;
      if (it.hasNext())
        unvisited = it.next();
      else
        unvisited = it.previous();

      it.remove();

      List<Node> children = getChildren(unvisited);
      for (Node child : children)
        it.add(child);

      visited.add(unvisited);
    }

    return visited;
  }

  private static List<Node> getChildren(Node n)
  {
    List<Node> children = asList(n.getChildNodes());
    Iterator<Node> it = children.iterator();
    while (it.hasNext())
      if (it.next().getNodeType() != Node.ELEMENT_NODE)
        it.remove();
    return children;
  }

  private static List<Node> asList(NodeList nodes)
  {
    List<Node> list = new ArrayList<Node>(nodes.getLength());
    for (int i = 0, l = nodes.getLength(); i < l; i++)
      list.add(nodes.item(i));
    return list;
  }

User · Answer

for  int i   0  i  lt  nodeList getLength    i     change to   for  int i   0  len   nodeList getLength    i  lt  len  i      to be more efficient   The second way of javanna answer may be the best as it tends to use a flatter  predictable memory model

User · Answer

Basically you have two ways to iterate over all elements   1  Using recursion  the most common way I think    public static void main String   args  throws SAXException  IOException          ParserConfigurationException  TransformerException        DocumentBuilderFactory docBuilderFactory   DocumentBuilderFactory          newInstance        DocumentBuilder docBuilder   docBuilderFactory newDocumentBuilder        Document document   docBuilder parse new File  document xml         doSomething document getDocumentElement        public static void doSomething Node node           do something with the current node instead of System out     System out println node getNodeName          NodeList nodeList   node getChildNodes        for  int i   0  i  lt  nodeList getLength    i              Node currentNode   nodeList item i           if  currentNode getNodeType      Node ELEMENT NODE                  calls this method for all the children which is Element             doSomething currentNode                       2  Avoiding recursion using getElementsByTagName   method with   as parameter   public static void main String   args  throws SAXException  IOException          ParserConfigurationException  TransformerException        DocumentBuilderFactory docBuilderFactory   DocumentBuilderFactory              newInstance        DocumentBuilder docBuilder   docBuilderFactory newDocumentBuilder        Document document   docBuilder parse new File  document xml          NodeList nodeList   document getElementsByTagName           for  int i   0  i  lt  nodeList getLength    i              Node node   nodeList item i           if  node getNodeType      Node ELEMENT NODE                   do something with the current element             System out println node getNodeName                         I think these ways are both efficient  Hope this helps

[java] Java: Most efficient method to iterate over all elements in a org.w3c.dom.Document?

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