How I can implement an algorithm that loops through a tree HTML with Java?

Question

I have to walk a tree that reaches me from a NodeList, I need an algorithm to traverse all nodes in order, most likely be in depth but not how to implement it. I think I need some recursion. Can anybody help?

The part of the code is: NodeList nodeLista = documento.getElementsByTagName("html");

for (int s = 0; s < nodeLista.getLength(); s++) {
    Node Raiz = nodeLista.item(s);

....

    for (int h = 0; h < nodeLista.getLength(); h++) {

    //Level of depth 1.
    Node Primer_Hijo = nodeLista.item(h); // In the first iteration for the HEAD will enter in the second iteration enter the BODY.

    //Level of depth 2.
    Element SegundoElemento = (Element) Primer_Hijo;
    NodeList ListadeNodos2 = SegundoElemento.getChildNodes();

.....

Answer 1

Recursive descent is exactly what you are looking for.

http://en.wikipedia.org/wiki/Recursive_descent_parser

Answer 2

For parsing html I have used Jerry in the past.

It bills itself as jquery for java and allows you to use css style selectors. I think there are now several libraries that implement css style selectors now.

It leads to more easily readable code though it might not fit your use case.

Answer 3

This is the pseudo code

    traverse_tree(node)   {
    childNodes = node.getChildNodes();
    if(chidNodes is empty){
      print valueOf(node);
      return;
    }
    for each childNode in childNodes{
     traverse_tree(childNode);
    }
}

Start traversal by calling traverse_tree(rootNode) //root is the tree root node.

Answer 4

Something like this:

public static void main(String[] args) {
    //get the nodeList
    //...
    for (int h = 0; h < nodeLista.getLength(); h++) {
        Node Primer_Hijo = nodeLista.item(h); 
        navegate(Primer_Hijo);
    }

    //or (better) the root node
    navegate(rootNode);
}

void navegate(Node node){
    //do something with node
    node.getAttributes();
    //...

    for(int i=0; i<node.getChildNodes().getLength(); i++)
        navegate(node.getChildNodes().item(i));
    }
}