计算机科学论坛--求助:有一个读取的程序,想写一个对应的写入的程序,帮帮我啊~~

这是一个在XML文件中读取Petri网信息的程序,现在想做相应的改变,变成将Petri网信息写入XML文件,谁能帮帮我吗?谢谢了哦~
import java.io.*;
import java.util.Vector;
import javax.xml.parsers.*;
import org.w3c.dom.*;

public class ReadPlace {
    static Document document;
    private boolean validating;

    public ReadPlace() {
    }

    public Vector toRead(String filename) {
       Vector <String>plabel=new Vector<String>();
       Vector <String>marking=new Vector<String>();

       String myStr=new String();

       try {
           DocumentBuilderFactory factory =
           DocumentBuilderFactory.newInstance();
           factory.setValidating(validating);
           DocumentBuilder builder = factory.newDocumentBuilder();
           Document doc = builder.parse(new File(filename));
           doc.normalize();

           NodeList list = doc.getElementsByTagName("place");
           for (int i = 0; i < list.getLength(); i++) {
               Element nodeitm = (Element)list.item(i);
               myStr=nodeitm.getElementsByTagName("label").item(0).getFirstChild().getNodeValue();
               plabel.addElement(myStr);
               myStr=nodeitm.getElementsByTagName("tokens").item(0).getFirstChild().getNodeValue();
               marking.addElement(myStr);
            }

        } catch (Exception exp) {
            exp.printStackTrace();
            return null;
        }

        Vector <Vector>all=new Vector<Vector>();
        all.addElement(plabel);
        all.addElement(marking);
        return all;
    }


}

///////

import java.util.Vector;

public class Demo{
public static void main(String[] args) {
       Vector A;
       ReadPlace my = new ReadPlace();
       A = my.toRead("tpn.xml");
       for (int i = 0; i < A.size(); i++) {
          System.out.println(A.elementAt(i));
       }
    }
}

///////

///////


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