Altering a DOM once it has been created after parseing an XML file

Question

Does anyone know of a nice easy way to edit a DOM once I have parsed it in so that I can write an altered XML file back to disk. (I can do the reading and writing easy enough, I just need the editing part.
I used to have code that worked if the child node you altered was directly off the root but I need something a bit more genric so that I can say:
replace(Document doc, String tag, String sub_tag, String item);
Where doc is the current DOM, tag is the main tag (not always the root), sub_tag is the specific tag I want to alter and item is the value I want to set the sub_tag to.
i.e. I want to read in XML like
<root>
<name>aname</name>
<blob>ablob</blob>
_{<name>subname</name>
<item>anitem</item>}
</root>
and have one method where I can change the root name or the sub name.
Any ideas ?

Answer 1

FYI here is how I did it in the end.
* Finds where the child tag we are looking for occurs and then replaces it with
* the a modified clone of the child.
* @param doc The Document to alter.
* @param parent_tag The tag to alter.
* @param child_tag The sub_tag that will be altered.
* @param item The item to insert as the value of a tag.
* @param index_one The index of the parent tag incase there is more than one.
* @param index_two The index of the child tag incase there is more than one.
* @return The modified document.
private Document putItemInDoc(Document doc, String parent_tag, String child_tag, String item, int index_one, int index_two)
Document tempDoc = doc;
Element root = tempDoc.getDocumentElement();
boolean found = false;
Node parent = null;
NodeList matches = tempDoc.getElementsByTagName(parent_tag);
//get the parent node we know the child to be on.
parent = matches.item(index_one);
NodeList childList = parent.getChildNodes();
int count = 0;
int i = 0;
do{
if((childList.item(i)).getNodeName().equals(child_tag))
if(count==index_two)
Node child = childList.item(i);
Node clone = child.cloneNode(true);
clone.getFirstChild().setNodeValue(item);
found = true;
System.out.println("found");
//replace child node with modified clone.
tempDoc.getElementsByTagName(parent_tag).item(index_one).replaceChild(clone,child);
else
count++;
i++;
}while((i<childList.getLength())&&(!found));
return(tempDoc);