/*******ReplaceText.java(Read intro.xml)*************/
import java.io.*;
import org.w3c.dom.*;
import javax.xml.parsers.*;
import org.apache.crimson.tree.XmlDocument;
import org.xml.sax.*;

public class ReplaceText
{
private Document document;

public ReplaceText()
{
  try
  {
   DocumentBuilderFactory factory=
    DocumentBuilderFactory.newInstance();
   factory.setValidating(true);
   DocumentBuilder builder=factory.newDocumentBuilder();
   builder.setErrorHandler(new MyErrorHandler());
   document=builder.parse(new File("intro.xml"));
   
   Node root=document.getDocumentElement();

   if (root.getNodeType()==Node.ELEMENT_NODE)
   {
    Element myMessageNode=(Element)root;
    NodeList messageNodes=myMessageNode.getElementsByTagName("message");

    if (messageNodes.getLength()!=0)
    {
     Node message=messageNodes.item(0);
     Text newText=document.createTextNode("New Changed Message!");
     Text oldText=(Text)message.getChildNodes().item(0);
     message.replaceChild(newText,oldText);
    }
   }
   ((XmlDocument)document).write(new FileOutputStream(intro1.xml));
  }catch(SAXParseException spe)
  {
   System.err.println("Parse Error:"+spe.getMessage());
   System.exit(1);
  }catch(SAXException se)
  {
   se.printStackTrace();
  }catch(FileNotFoundException fne)
  {
   System.err.println("File \'intro.xml\' not Found.");
   System.exit(1);
  }catch(Exception e)
  {
   e.printStackTrace();
  }
}

public static void main(String args[])
{
  ReplaceText d=new ReplaceText();
}
};

/************Error Handler for validation errors.***********/
import org.xml.sax.ErrorHandler;
import org.xml.sax.SAXException;
import org.xml.sax.SAXParseException;

public class MyErrorHandler implements ErrorHandler
{
public void fatalError(SAXParseException exception)throws SAXException
{
  throw exception;
}
public void error(SAXParseException e)throws SAXParseException
{
  throw e;
}
public void warning(SAXParseException err)throws SAXParseException
{
  System.err.println("Warning:"+err.getMessage());
}
};

运行:javac ReplaceText.java MyErrorHandler.java
编译通过了
运行:java ReplaceText
提示错误:java.lang.ClassCastException
错误指向这两行:
((XmlDocument)document).write(new FileOutputStream(intro1.xml));
ReplaceText d=new ReplaceText();

请问该怎样解决呢?

import java.io.*;
import org.w3c.dom.*;
import javax.xml.parsers.*;
//import com.sun.xml.tree.XmlDocument;
import org.apache.crimson.tree.XmlDocument;
import org.xml.sax.*;

public class ReplaceText {
   private Document document;

   public ReplaceText()
   {
      try {

         // obtain the default parser
         DocumentBuilderFactory factory =
            DocumentBuilderFactory.newInstance();

         // set the parser to validating           
         factory.setValidating( true );
     
         DocumentBuilder builder = factory.newDocumentBuilder();

         // set error handler for validation errors
         builder.setErrorHandler( new MyErrorHandler() );

         // obtain document object from XML document
         document = builder.parse( new File( "intro.xml" ) );

         // fetch the root node
         Node root = document.getDocumentElement();

         if ( root.getNodeType() == Node.ELEMENT_NODE ) {
            Element myMessageNode = ( Element ) root;
            NodeList messageNodes =
               myMessageNode.getElementsByTagName( "message" );

            if ( messageNodes.getLength() != 0 ) {
               Node message = messageNodes.item( 0 );

               // create a text node
               Text newText = document.createTextNode(
                                "New Changed Message!!" );

               // get the old text node
               Text oldText =
                  ( Text ) message.getChildNodes().item( 0 );  

               // replace the text
               message.replaceChild( newText, oldText );
            }
         }            
        
         ( (XmlDocument) document).write( new FileOutputStream(
             "intro2.xml" ) );  
      }
      catch ( SAXParseException spe ) {
         System.err.println( "Parse error: " +
            spe.getMessage() );
         System.exit( 1 );
      }
      catch ( SAXException se ) {
         se.printStackTrace();         
      }
      catch ( FileNotFoundException fne ) {
         System.err.println( "File \'intro.xml\' not found. " );
         System.exit( 1 );
      }
      catch ( Exception e ) {
         e.printStackTrace();
      }
   }
   
   public static void main( String args[] )
   {
      ReplaceText d = new ReplaceText();    
   }
}

import java.io.*;
import org.w3c.dom.*;
import org.xml.sax.*;
import javax.xml.parsers.*;
import org.apache.crimson.tree.XmlDocument;

public class BuildXml
{
 private Document document;
 
 public BuildXml()
 {
  DocumentBuilderFactory factory=DocumentBuilderFactory.newInstance();
  try
  {
   DocumentBuilder builder=factory.newDocumentBuilder();
   document=builder.newDocument();
  }catch(ParserConfigurationException pce)
  {
   pce.printStackTrace();
  }
  
  Element root=document.createElement("root");
  document.appendChild(root);
  
  Comment simpleComment=document.createComment("This is a simple contact list");
  root.appendChild(simpleComment);

  Node contactNode=createContactNode(document);
  root.appendChild(contactNode);

  ProcessingInstruction pi=document.createProcessingInstruction("myInstruction","action list");
  root.appendChild(pi);

  CDATASection cdata=document.createCDATASection("I can add <, >, and ?" );
  root.appendChild(cdata);

  try
  {
   ((XmlDocument)document).write(new FileOutputStream("myDocument.xml"));
  }catch(IOException ioe)
  {
   ioe.printStackTrace();
  }
 }

 public Node createContactNode(Document document)
 {
  Element firstElement=document.createElement("FirstName");
  Element lastElement=document.createElement("LastName");

  firstElement.appendChild(document.createTextNode("Sue"));
  lastElement.appendChild(document.createTextNode("Green"));

  Element contact=document.createElement("contact");

  Attr genderAttribute=document.createAttribute("gender");
  genderAttribute.setValue("F");

  contact.setAttributeNode(genderAttribute);
  contact.appendChild(firstElement);
  contact.appendChild(lastElement);
  
  return contact;
 }

 public static void main(String args[])
 {
  BuildXml buildXml=new BuildXml();
 }
};

另外XmlDocument这个文件在书上是import com.sun.xml.tree.XmlDocument;
而我找不到这个...用import org.apache.crimson.tree.XmlDocument;这个替代...
值得注意的是:XmlDocument.class这个文件在很多地方都有,比如在F:\oracle\ora90\oem_webstage\oracle\xml\parser\v2里面也有XmlDocument.class这个文件...它跟org.apache.crimson.tree.XmlDocument这个大小是不一样的
我认为用"import org.apache.crimson.tree.XmlDocument;"这个替代"import com.sun.xml.tree.XmlDocument;"是不正确的...但我又找不到"import com.sun.xml.tree.XmlDocument;"这个文件.
大家帮帮忙啊...我两个星期了都无法解决这个问题....谢谢!

不知道这样说能否对你有所帮助？