remove node from XML file java program

Question

When I try to remove a node from XML node from java program it is giving me a strange problem. It is removing alternate nodes. I have to remove existing nodes before inserting new nodes. my xml file is:

<?xml version="1.0" encoding="windows-1252" ?>
<chart>
<categories>
 <category label="3 seconds"/>
 <category label="6 seconds"/>
 <category label="9 seconds"/>
 <category label="12 seconds"/>
</categories>

</chart>

my java program is:

      DocumentBuilderFactory  docFactory  = DocumentBuilderFactory.newInstance();
      DocumentBuilder docBuilder = docFactory.newDocumentBuilder();

      Document doc = docBuilder.parse(filePath);


      Node categories = doc.getElementsByTagName("categories").item(0);

      NodeList categorieslist = categories.getChildNodes();

      // if exists delete old data the insert new data.


      for (int c = 0; c < categorieslist.getLength(); c++) {

        Node node = categorieslist.item(c);
        categories.removeChild(node);
      }
    for(int i=1;i<20;i++){

    Element category = doc.createElement("category");
    category.setAttribute("label",3*i+" seconds");
    categories.appendChild(category);
  }

This code is deleting alternative nodes I don't know why. The resulting XML is showing like this:

<categories>
 <category label="6 seconds"/>
 <category label="12 seconds"/>
 <category label="3 seconds"/>
 <category label="6 seconds"/>
 <category label="9 seconds"/>
      .....
      .....
 </categories>

when i try to print c value from for loop it is printing only half of the size of list value. — mallikarjun
– mallikarjun, Commented Jul 10, 2012 at 11:12
It is solved when i doesn't increment "c" value in loop. but i don't know why can somebody please explain me. — mallikarjun
– mallikarjun, Commented Jul 10, 2012 at 11:17
When you delete node 0, all nodes shift left. So node one becomes node 0. Then you attempt to delete node 1, nut never go back to delete node 0 again. So you completely missed the original node 1. — GC_
– GC_, Commented Sep 8, 2013 at 21:36

Anton · Accepted Answer · 2012-07-10 14:41:57Z

6

Every time you remove a child the list becomes shorter, the list isn't a static collections, so every time you call getLength() you get the actual size

Node categories = doc.getElementsByTagName("categories").item(0);
NodeList categorieslist = categories.getChildNodes();
while (categorieslist.getLength() > 0) {
    Node node = categorieslist.item(0);
    node.getParentNode().removeChild(node);
}

answered Jul 10, 2012 at 14:41

Anton

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mallikarjun Over a year ago

but why it is deleting alternative nodes

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