How to merge two XML's with JDOM?

Question

How to merge two xmls's using jdom? like:
is there a way to add the complete content one xml into the parent node of another xml?
//in.xml
<?xml version="1.0"?>
<people>
<person>
  <name>ABC</name>
  <email>[email protected]</email>
</person>
</people>
//out.xml
<?xml version="1.0"?>
<address>
<city> abccounty</city>
<state> abcstate</state>
</address>
Merged XML:
<?xml version="1.0"?>
<people>
<person>
  <name>xyz</name>
  <email>[email protected]</email>
</person>
<address>
<city> abccounty</city>
<state> abcstate</state>
</address>
</people>
import java.util.List;
import org.jdom.Document;
import org.jdom.Element;
import org.jdom.input.SAXBuilder;
import org.jdom.output.Format;
import org.jdom.output.XMLOutputter;
public class MergeXMLS {
     public static void main(String[] args) {
          try{
              SAXBuilder builder = new SAXBuilder();
              Document books = builder.build("D:/in.xml");
              Document onebook = builder.build("D:/out.xml");
              Element root = books.getRootElement();
              List rows = root.getChildren();
              for (int i = 0; i < rows.size(); i++) {
                  Element row = (Element) rows.get(i);
                  onebook.getRootElement().addContent(row.detach());
                  System.out.println(row.getName());
              new XMLOutputter(Format.getPrettyFormat()).output(onebook, System.out);
          }catch(Exception e){
               e.printStackTrace();
}

Answer 1

The above code only add's the first node.
I changed the code little differently to
              SAXBuilder builder = new SAXBuilder();
              Document books = builder.build("D:/in.xml");
              Document onebook = builder.build("D:/out.xml");
             //trying to add second xml into the first
              books.getRootElement().addContent(onebook.getRootElement().getContent()); 
              new XMLOutputter(Format.getPrettyFormat()).output(books, System.out);
here is the exception from the above code:
org.jdom.IllegalAddException: The Content already has an existing parent "address"
     at org.jdom.ContentList.add(ContentList.java:218)
     at org.jdom.ContentList.add(ContentList.java:140)