[HELP! ] why my program thows a javax.swing.text.ChangedCharSetException?

Question

there's the source:
import java.io.*;
import java.util.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
import javax.swing.text.*;
import javax.swing.text.html.*;
import javax.swing.border.*;
class HTMLMagician extends JFrame
     protected static final String APP_NAME="HTML Magician V1.0 Produced By V Studio";
     protected JTextPane hm_textPane;
     protected StyleSheet hm_styleSheet;
     protected HTMLEditorKit html_kit;
     protected HTMLDocument html_document;
     protected JMenuBar hm_menuBar;
     protected JToolBar hm_toolBar;
     protected JFileChooser hm_fileChooser;
     protected File current_file;
     protected boolean text_changed=false;
     public HTMLMagician()
          super(APP_NAME);
          setSize(800,600);
          getContentPane().setLayout(new BorderLayout());
          produceMenuBar();
          hm_textPane=new JTextPane();
          html_kit=new HTMLEditorKit();
          hm_textPane.setEditorKit(html_kit);
          JScrollPane textPane_scrollPane=new JScrollPane();
          textPane_scrollPane.getViewport().add(hm_textPane);
          getContentPane().add(textPane_scrollPane,BorderLayout.CENTER);
          hm_fileChooser=new JFileChooser();
          javax.swing.filechooser.FileFilter hm_filter=new javax.swing.filechooser.FileFilter()
               public boolean accept(File pathname)
                    if(pathname.isDirectory())
                         return true;
                    String ext_name=pathname.getName().toLowerCase();
                    if(ext_name.endsWith(".htm"))
                         return true;
                    if(ext_name.endsWith(".html"))
                         return true;
                    if(ext_name.endsWith(".asp"))
                         return true;
                    if(ext_name.endsWith(".jsp"))
                         return true;
                    if(ext_name.endsWith(".css"))
                         return true;
                    if(ext_name.endsWith(".php"))
                         return true;
                    if(ext_name.endsWith(".aspx"))
                         return true;
                    if(ext_name.endsWith(".xml"))
                         return true;
                    if(ext_name.endsWith(".txt"))
                         return true;
                    return false;
               public String getDescription()
                    return "HTML files(*.htm,*.html,*.asp,*.jsp,*.css,*.php,*.aspx,*.xml)";
          hm_fileChooser.setAcceptAllFileFilterUsed(false);
          hm_fileChooser.setFileFilter(hm_filter);
          try
               File dir=(new File(".")).getCanonicalFile();
               hm_fileChooser.setCurrentDirectory(dir);
          }catch(IOException ex)
               showError(ex,"Error openning current directory");
          newDocument();
          WindowListener action_winClose=new WindowAdapter()
               public void windowClosing(WindowEvent evt)
                    if(!promptToSave())
                         return;
                    System.exit(0);
          addWindowListener(action_winClose);
          setDefaultCloseOperation(JFrame.DO_NOTHING_ON_CLOSE);
          setVisible(true);
     protected void produceMenuBar()
          hm_menuBar=new JMenuBar();
          hm_toolBar=new JToolBar();
          JMenu menu_file=new JMenu("File");
          menu_file.setMnemonic('f');
          ImageIcon icon_new=new ImageIcon("imgs/file.gif");
          Action action_new=new AbstractAction("New",icon_new)
               public void actionPerformed(ActionEvent evt)
                    if(!promptToSave())
                         return;
                    newDocument();
          JMenuItem item_new=new JMenuItem(action_new);
          item_new.setMnemonic('n');
          item_new.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_N,InputEvent.CTRL_MASK));
          menu_file.add(item_new);
          JButton button_new=hm_toolBar.add(action_new);
          ImageIcon icon_open=new ImageIcon("imgs/folder_open.gif");
          Action action_open=new AbstractAction("Open...",icon_open)
               public void actionPerformed(ActionEvent evt)
                    if(!promptToSave())
                         return;
                    openDocument();
          JMenuItem item_open=new JMenuItem(action_open);
          item_open.setMnemonic('o');
          item_open.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_O,InputEvent.CTRL_MASK));
          menu_file.add(item_open);
          JButton button_open=hm_toolBar.add(action_open);
          ImageIcon icon_save=new ImageIcon("imgs/floppy.gif");
          Action action_save=new AbstractAction("Save",icon_save)
               public void actionPerformed(ActionEvent evt)
                    saveAs(false);
          JMenuItem item_save=new JMenuItem(action_save);
          item_save.setMnemonic('s');
          item_save.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_S,InputEvent.CTRL_MASK));
          menu_file.add(item_save);
          JButton button_save=hm_toolBar.add(action_save);
          Action action_saveAs=new AbstractAction("Save As...")
               public void actionPerformed(ActionEvent evt)
                    saveAs(true);
          JMenuItem item_saveAs=new JMenuItem(action_saveAs);
          item_saveAs.setMnemonic('a');
          item_saveAs.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_A,InputEvent.CTRL_MASK));
          menu_file.add(item_saveAs);
          menu_file.addSeparator();
          Action action_close=new AbstractAction("Quit")
               public void actionPerformed(ActionEvent evt)
                    if(!promptToSave())
                         return;
                    System.exit(0);
          JMenuItem item_exit=new JMenuItem(action_close);
          item_exit.setMnemonic('q');
          item_exit.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_Q,InputEvent.CTRL_MASK));
          menu_file.add(item_exit);
          hm_menuBar.add(menu_file);
          setJMenuBar(hm_menuBar);
          getContentPane().add(hm_toolBar,BorderLayout.NORTH);
     protected String getDocumentName()
          return current_file==null ? "Untitled" : current_file.getName();
     protected void newDocument()
          html_document=(HTMLDocument)html_kit.createDefaultDocument();
          hm_styleSheet=html_document.getStyleSheet();
          hm_textPane.setDocument(html_document);
          current_file=null;
          setTitle(getDocumentName()+" - "+APP_NAME);
          Runnable runner=new Runnable()
               public void run()
                    text_changed=false;
                    html_document.addDocumentListener(new action_textChanged());
          SwingUtilities.invokeLater(runner);
     protected void openDocument()
          if(hm_fileChooser.showOpenDialog(HTMLMagician.this)!=JFileChooser.APPROVE_OPTION)
               return;
          File f=hm_fileChooser.getSelectedFile();
          if(f==null || !f.isFile())
               return;
          current_file=f;
          setTitle(getDocumentName()+" - "+APP_NAME);
          HTMLMagician.this.setCursor(Cursor.getPredefinedCursor(Cursor.WAIT_CURSOR));
          try
               InputStream in=new FileInputStream(current_file);
               html_document=(HTMLDocument)html_kit.createDefaultDocument();
               html_kit.read(in,html_document,0);
               hm_styleSheet=html_document.getStyleSheet();
               hm_textPane.setDocument(html_document);
               in.close();
          }catch(Exception ex)
               showError(ex,"Error openning file "+current_file);
          HTMLMagician.this.setCursor(Cursor.getPredefinedCursor(Cursor.DEFAULT_CURSOR));
          Runnable runner=new Runnable()
               public void run()
                    text_changed=false;
                    html_document.addDocumentListener(new action_textChanged());
          SwingUtilities.invokeLater(runner);
     protected boolean saveAs(boolean as)
          if(!as && !text_changed)
               return true;
          if(as || current_file==null)
               if(hm_fileChooser.showSaveDialog(HTMLMagician.this)!=JFileChooser.APPROVE_OPTION)
                    return false;
               File f=hm_fileChooser.getSelectedFile();
               if(f==null || !f.isFile())
                    return false;
               current_file=f;
               setTitle(getDocumentName()+" - "+APP_NAME);
          HTMLMagician.this.setCursor(Cursor.getPredefinedCursor(Cursor.WAIT_CURSOR));
          try
               OutputStream out=new FileOutputStream(current_file);
               html_kit.write(out,html_document,0,html_document.getLength());
               out.close();
          }catch(Exception ex)
               showError(ex,"Error saving file "+current_file);
          HTMLMagician.this.setCursor(Cursor.getPredefinedCursor(Cursor.DEFAULT_CURSOR));
          return true;
     protected boolean promptToSave()
          if(!text_changed)
               return true;
          int result=JOptionPane.showConfirmDialog(this,"Save change to "+getDocumentName(),APP_NAME,JOptionPane.YES_NO_CANCEL_OPTION,JOptionPane.INFORMATION_MESSAGE);
          switch(result)
               case JOptionPane.YES_OPTION:
                    if(!saveAs(false))
                         return false;
                    return true;
               case JOptionPane.NO_OPTION:
                    return true;
               case JOptionPane.CANCEL_OPTION:
                    return false;
          return true;
     protected void showError(Exception ex,String message)
          ex.printStackTrace();
          JOptionPane.showMessageDialog(this,message,APP_NAME,JOptionPane.WARNING_MESSAGE);
     public static void main(String[] args)
          new HTMLMagician();
     class action_textChanged implements DocumentListener
          public void changedUpdate(DocumentEvent evt)
               text_changed=true;
          public void insertUpdate(DocumentEvent evt)
               text_changed=true;
          public void removeUpdate(DocumentEvent evt)
               text_changed=true;
when i open a .html file,the command output :
javax.swing.text.ChangedCharSetException
     at javax.swing.text.html.parser.DocumentParser.handleEmptyTag(Unknown Source)
     at javax.swing.text.html.parser.Parser.startTag(Unknown Source)
     at javax.swing.text.html.parser.Parser.parseTag(Unknown Source)
     at javax.swing.text.html.parser.Parser.parseContent(Unknown Source)
     at javax.swing.text.html.parser.Parser.parse(Unknown Source)
     at javax.swing.text.html.parser.DocumentParser.parse(Unknown Source)
     at javax.swing.text.html.parser.ParserDelegator.parse(Unknown Source)
     at javax.swing.text.html.HTMLEditorKit.read(Unknown Source)
     at javax.swing.text.DefaultEditorKit.read(Unknown Source)
     at HTMLMagician.openDocument(HTMLMagician.java:222)
     at HTMLMagician$4.actionPerformed(HTMLMagician.java:128)
     at javax.swing.AbstractButton.fireActionPerformed(Unknown Source)
     at javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source)
     at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source)
     at javax.swing.DefaultButtonModel.setPressed(Unknown Source)
     at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(Unknown Source)
     at java.awt.Component.processMouseEvent(Unknown Source)
     at javax.swing.JComponent.processMouseEvent(Unknown Source)
     at java.awt.Component.processEvent(Unknown Source)
     at java.awt.Container.processEvent(Unknown Source)
     at java.awt.Component.dispatchEventImpl(Unknown Source)
     at java.awt.Container.dispatchEventImpl(Unknown Source)
     at java.awt.Component.dispatchEvent(Unknown Source)
     at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
     at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
     at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
     at java.awt.Container.dispatchEventImpl(Unknown Source)
     at java.awt.Window.dispatchEventImpl(Unknown Source)
     at java.awt.Component.dispatchEvent(Unknown Source)
     at java.awt.EventQueue.dispatchEvent(Unknown Source)
     at java.awt.EventDispatchThread.pumpOneEventForHierarchy(Unknown Source)
     at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
     at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
     at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
     at java.awt.EventDispatchThread.run(Unknown Source)
why? what's wrong? thanks

Answer 1

The DocumentParser seems to throw a ChangedCharSetException if it finds a "http-equiv" meta tag for "content-type" or "charset" and if the parser's "ignoreCharSet" property is set to false on creation.