java怎样读写和修改XML文件？？

<?xml version="1.0" encoding="UTF-8"?>   
  
<users>   
  
<Messages>   
<sendName>sendUsers</sendName>   
<receiveName>snake</receiveName>   
<date>2007-12-04 12:20:00</date>   
<status>0</status>   
<message>this is Content</message>   
</Messages>   
  
</users>  

package com.lianxi.DAO;   
import java.io.File;   
  
import javax.xml.parsers.DocumentBuilder;   
import javax.xml.parsers.DocumentBuilderFactory;   
import javax.xml.transform.Transformer;   
import javax.xml.transform.TransformerFactory;   
import javax.xml.transform.dom.DOMSource;   
import javax.xml.transform.stream.StreamResult;   
  
import org.w3c.dom.Document;   
import org.w3c.dom.Node;   
import org.w3c.dom.NodeList;   
public class UpdateXml {   
 public static boolean doc2XmlFile(Document document,String filename)    
    {    
      boolean flag = true;    
      try    
       {    
            /** 将document中的内容写入文件中   */    
             TransformerFactory tFactory = TransformerFactory.newInstance();       
             Transformer transformer = tFactory.newTransformer();     
            /** 编码 */    
            //transformer.setOutputProperty(OutputKeys.ENCODING, "GB2312");    
             DOMSource source = new DOMSource(document);     
             StreamResult result = new StreamResult(new File(filename));       
             transformer.transform(source, result);     
         }catch(Exception ex)    
         {    
             flag = false;    
             ex.printStackTrace();    
         }    
        return flag;          
    }   
    
 public static Document load(String filename)    
    {    
       Document document = null;    
      try     
       {     
            DocumentBuilderFactory   factory = DocumentBuilderFactory.newInstance();       
            DocumentBuilder builder=factory.newDocumentBuilder();       
            document=builder.parse(new File(filename));       
            document.normalize();    
       }    
      catch (Exception ex){    
           ex.printStackTrace();    
       }      
      return document;    
    }   
   /**   
     *   演示修改文件的具体某个节点的值    
     */    
   public static void xmlUpdateDemo()    
    {    
       Document document = load("c://Message.xml");    
       Node root=document.getDocumentElement();    
      /** 如果root有子元素 */    
      if(root.hasChildNodes())    
       {    
         /** ftpnodes */    
          NodeList ftpnodes = root.getChildNodes();    
         /** 循环取得ftp所有节点 */    
         for (int i=0;i<ftpnodes.getLength();i++)    
          {                          
             NodeList ftplist = ftpnodes.item(i).getChildNodes();    
            for (int k=0;k<ftplist.getLength();k++)    
             {    
               Node subnode = ftplist.item(k);    
              /** 删除ftp-chn节点 */    
//              if (subnode.getNodeType()==Node.ELEMENT_NODE&&subnode.getNodeName()=="ftp-chn")    
//               {    
//                  ftpnodes.item(i).removeChild(subnode);    
//               }    
              /** 修改ftp-host的值为 192.168.0.1 */    
              if (subnode.getNodeType()==Node.ELEMENT_NODE&&subnode.getNodeName()=="status")    
               {                     
                  subnode.getFirstChild().setNodeValue("1");    
               }    
             }    
                
          }    
       }    
        
       doc2XmlFile(document,"c://Message.xml");    
    }   
   public static void main(String args[])throws Exception   
   {   
    UpdateXml.xmlUpdateDemo();   
   }   
}