借这里人气 问下：怎么用jdom 怎么在xml中写入重复元素

/*例子实现这个xml:
<HVTR>
<RBIF>
<RINM>报告机构名称</RINM>
</RBIF>

<CATIs>
<CATI seqno=”1”>
<CTIF>
<CTNM>客户名称</CTNM>
<CITP>客户身份证件类型</CITP>
</CTIF>
</CATI>
………(循环CATI) 问题就在这里,做循环时属性值累加,但是元素不变,编译的时候没有问题,运行的时候报错:The Content already has an existing parent "CATI"
</CATIs>
</HVTR>
*/

import java.io.*;
import org.jdom.*;
import org.jdom.input.*;
import org.jdom.input.*;
import org.jdom.output.*;
public class xmlwriter {
public void writer() throws IOException,JDOMException {
int i=1;
Element root,r2,r3,r1,r4,r5;
Document Doc;
root = new Element("HVTR");
Doc = new Document(root);
root.addContent(new Comment("这是注释"));
root.addContent(new Element("RBIF").addContent(new Element("RINM").addContent("报告机构名称")));
r1 = new Element("CATIs");
r2 = new Element("CATI");
r3 = new Element("CTIF");
r4 = new Element("CTNM");
r5 = new Element("CITP");
r4.addContent("客户名称");
r5.addContent("客户身份证件类型");
r3.addContent(r4);
r3.addContent(r5);
for(i=1;i<=10;i++){
String num=Integer.toString(i);
r2.addContent(r3).setAttribute("seqno", num);
}
r1.addContent(r2);
root.addContent(r1);

Format format = Format.getPrettyFormat();
format.setEncoding("GB2312");
XMLOutputter Outputter = new XMLOutputter();
Outputter.setFormat(format);
Outputter.output(Doc, new FileOutputStream("test1.xml"));
}
public static void main(String[] args) {
try {
xmlwriter s1 = new xmlwriter();
System.out.println("Now we build an XML document .....");
s1.writer();
}
catch (Exception e) {
System.out.println(e.getMessage());
}
}
}