Syntax Highlighting and Undo Problem

Question

Hello Guys. I am working ona very simple type of Java Code Editor with syntax highlighting feature. It works fine as far as the syntax highlighting, cut, copy, paste etc are concerned but when I added Undo, Redo feature, it was not working as Undo Redo should. The UndoManager first removes the text attributes and finally the main Undo job. For example if I paste word public , the UndoManager will first remove the attributes and after about third or fouth click on the Undo button removes the pasted word.
Please Help.

Answer 1

Here's the complete demo code.
import java.awt.*;
import java.awt.event.*;
import java.util.*;
import javax.swing.*;
import javax.swing.text.*;
import javax.swing.event.*;
import javax.swing.text.rtf.*;
import javax.swing.undo.*;
class ColorTextInTextPane extends JFrame implements UndoableEditListener
     private Hashtable keywords,impclasses;
     JEditorPane edit;
     UndoManager undo;
     JButton undoIt, redoIt;
     JPanel southButtonPanel;
     MyDocument doc = new MyDocument();
     public ColorTextInTextPane()
          super("ColorTextInTextPane");
          this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
          edit = new JEditorPane();
          edit.setEditorKit(new StyledEditorKit());
          edit.setEditable(true);
          doc.addUndoableEditListener(this);
          edit.setDocument(doc);
          JScrollPane scroll=new JScrollPane(edit);
          undo = new UndoManager();
          undoIt = new JButton("Undo");
          undoIt.addActionListener(new ActionListener()
            public void actionPerformed(ActionEvent ae)
                undoAction(ae);
          redoIt = new JButton("Redo");
          redoIt.addActionListener(new ActionListener()
            public void actionPerformed(ActionEvent ae)
                redoAction(ae);
          southButtonPanel = new JPanel();
          southButtonPanel.add(undoIt);
          southButtonPanel.add(redoIt);
          getContentPane().add(scroll);
          getContentPane().add(southButtonPanel, BorderLayout.SOUTH);
          setSize(300,300);
          setVisible(true);
          Object dummyObject = new Object();
          keywords = new Hashtable();
          keywords.put( "abstract", dummyObject );
          keywords.put( "boolean", dummyObject );
          keywords.put( "break", dummyObject );
          keywords.put( "byte", dummyObject );
          keywords.put( "byvalue", dummyObject );
          keywords.put( "case", dummyObject );
          keywords.put( "cast", dummyObject );
          keywords.put( "catch", dummyObject );
          keywords.put( "char", dummyObject );
          keywords.put( "class", dummyObject );
          keywords.put( "const", dummyObject );
          keywords.put( "continue", dummyObject );
          keywords.put( "default", dummyObject );
          keywords.put( "do", dummyObject );
          keywords.put( "double", dummyObject );
          keywords.put( "else", dummyObject );
          keywords.put( "extends", dummyObject );
          keywords.put( "false", dummyObject );
          keywords.put( "final", dummyObject );
          keywords.put( "finally", dummyObject );
          keywords.put( "float", dummyObject );
          keywords.put( "for", dummyObject );
          keywords.put( "future", dummyObject );
          keywords.put( "generic", dummyObject );
          keywords.put( "goto", dummyObject );
          keywords.put( "if", dummyObject );
          keywords.put( "implements", dummyObject );
          keywords.put( "import", dummyObject );
          keywords.put( "inner", dummyObject );
          keywords.put( "instanceof", dummyObject );
          keywords.put( "int", dummyObject );
          keywords.put( "interface", dummyObject );
          keywords.put( "long", dummyObject );
          keywords.put( "native", dummyObject );
          keywords.put( "new", dummyObject );
          keywords.put( "null", dummyObject );
          keywords.put( "operator", dummyObject );
          keywords.put( "outer", dummyObject );
          keywords.put( "package", dummyObject );
          keywords.put( "private", dummyObject );
          keywords.put( "protected", dummyObject );
          keywords.put( "public", dummyObject );
          keywords.put( "rest", dummyObject );
          keywords.put( "return", dummyObject );
          keywords.put( "short", dummyObject );
          keywords.put( "static", dummyObject );
          keywords.put( "super", dummyObject );
          keywords.put( "switch", dummyObject );
          keywords.put( "synchronized", dummyObject );
          keywords.put( "this", dummyObject );
          keywords.put( "throw", dummyObject );
          keywords.put( "throws", dummyObject );
          keywords.put( "transient", dummyObject );
          keywords.put( "true", dummyObject );
          keywords.put( "try", dummyObject );
          keywords.put( "var", dummyObject );
          keywords.put( "void", dummyObject );
          keywords.put( "volatile", dummyObject );
          keywords.put( "while", dummyObject );
          Object dummyObject1 = new Object();
          impclasses = new Hashtable();
          impclasses.put( "JFrame", dummyObject1);
          impclasses.put( "Applet", dummyObject1);
                impclasses.put( "JApplet", dummyObject1);
                impclasses.put( "JTextField", dummyObject1);
                impclasses.put( "JLabel", dummyObject1);
                impclasses.put( "JPanel", dummyObject1);
                impclasses.put( "JButton", dummyObject1);
     public void undoableEditHappened(UndoableEditEvent ev) {
    undo.addEdit(ev.getEdit());
    updateMenu();
  void undoAction(ActionEvent e) {
    try {
      if (undo.canUndo())
        undo.undo();
      updateMenu();
    catch (CannotRedoException cre) {
  void redoAction(ActionEvent e)
    try {
      if (undo.canRedo())
        undo.redo();
      updateMenu();
    catch (CannotRedoException cre) {
  public void updateMenu()
    undoIt.setEnabled(undo.canUndo());
    redoIt.setEnabled(undo.canRedo());
     public static void main(String a[])
          new ColorTextInTextPane();
     class MyDocument extends DefaultStyledDocument
          DefaultStyledDocument doc;
          MutableAttributeSet normal;
          MutableAttributeSet keyword;
          MutableAttributeSet comment;
          MutableAttributeSet quote;
          MutableAttributeSet impclasses1;
          public MyDocument()
               doc = this;
               putProperty( DefaultEditorKit.EndOfLineStringProperty, "\n" );
               normal = new SimpleAttributeSet();
               StyleConstants.setForeground(normal, Color.black);
               comment = new SimpleAttributeSet();
               StyleConstants.setForeground(comment, Color.green);
               StyleConstants.setItalic(comment, true);
               keyword = new SimpleAttributeSet();
               StyleConstants.setForeground(keyword, Color.blue);
               StyleConstants.setBold(keyword, true);
               quote = new SimpleAttributeSet();
               StyleConstants.setForeground(quote, Color.red);
               StyleConstants.setBold(quote, true);
               impclasses1 = new SimpleAttributeSet();
               StyleConstants.setForeground(impclasses1, Color.magenta);
               StyleConstants.setBold(impclasses1, true);
          public void insertString(int offset, String str, AttributeSet a) throws BadLocationException
               super.insertString(offset, str, a);
               processChangedLines(offset, str.length());
          public void remove(int offset, int length) throws BadLocationException
               super.remove(offset, length);
               processChangedLines(offset, 0);
          public void processChangedLines(int offset, int length) throws BadLocationException
               String content = doc.getText(0, doc.getLength());
               Element root = doc.getDefaultRootElement();
               int startLine = root.getElementIndex( offset );
               int endLine = root.getElementIndex( offset + length );
               for (int i = startLine; i <= endLine; i++)
                    int startOffset = root.getElement( i ).getStartOffset();
                    int endOffset = root.getElement( i ).getEndOffset();
                    applyHighlighting(content, startOffset, endOffset - 1);
          public void applyHighlighting(String content, int startOffset, int endOffset)
               throws BadLocationException
               int index;
               int lineLength = endOffset - startOffset;
               int contentLength = content.length();
               if (endOffset >= contentLength)
                    endOffset = contentLength - 1;
               //  set normal attributes for the line
               doc.setCharacterAttributes(startOffset, lineLength, normal, true);
               //  check for multi line comment
               String multiLineStartDelimiter = "/*";
               String multiLineEndDelimiter = "*/";
               index = content.lastIndexOf( multiLineStartDelimiter, endOffset );
               if (index > -1)
                    int index2 = content.indexOf( multiLineEndDelimiter, index );
                    if ( (index2 == -1) || (index2 > endOffset) )
                         doc.setCharacterAttributes(index, endOffset - index + 1, comment, false);
                         return;
                    else
                    if (index2 >= startOffset)
                         doc.setCharacterAttributes(index, index2 + 2 - index, comment, false);
                         return;
               //  check for single line comment
               String singleLineDelimiter = "//";
               index = content.indexOf( singleLineDelimiter, startOffset );
               if ( (index > -1) && (index < endOffset) )
                    doc.setCharacterAttributes(index, endOffset - index + 1, comment, false);
                    endOffset = index - 1;
               //  check for tokens
               checkForTokens(content, startOffset, endOffset);
          private void checkForTokens(String content, int startOffset, int endOffset)
               while (startOffset <= endOffset)
                    //  find the start of a new token
                    while ( isDelimiter( content.substring(startOffset, startOffset + 1) ) )
                         if (startOffset < endOffset)
                              startOffset++;
                         else
                              return;
                    if ( isQuoteDelimiter( content.substring(startOffset, startOffset + 1) ) )
                         startOffset = getQuoteToken(content, startOffset, endOffset);
                    else
                         startOffset = getOtherToken(content, startOffset, endOffset);
          private boolean isDelimiter(String character)
               String operands = ";:{}()[]+-/%<=>!&|^~*";
             if (Character.isWhitespace( character.charAt(0) ) ||
                  operands.indexOf(character) != -1 )
                  return true;
             else
                  return false;
          private boolean isQuoteDelimiter(String character)
               String quoteDelimiters = "\"'";
               if (quoteDelimiters.indexOf(character) == -1)
                  return false;
             else
                  return true;
          private boolean isKeyword(String token)
               Object o = keywords.get( token );
               return o == null ? false : true;
          private boolean isimpclasses1(String token)
               Object o = impclasses.get( token );
               return o == null ? false : true;
          private int getQuoteToken(String content, int startOffset, int endOffset)
               String quoteDelimiter = content.substring(startOffset, startOffset + 1);
               String escapedDelimiter = "\\" + quoteDelimiter;
               int index;
               int endOfQuote = startOffset;
               //  skip over the escaped quotes in this quote
               index = content.indexOf(escapedDelimiter, endOfQuote + 1);
               while ( (index > -1) && (index < endOffset) )
                    endOfQuote = index + 1;
                    index = content.indexOf(escapedDelimiter, endOfQuote);
               // now find the matching delimiter
               index = content.indexOf(quoteDelimiter, endOfQuote + 1);
               if ( (index == -1) || (index > endOffset) )
                    endOfQuote = endOffset;
               else
                    endOfQuote = index;
               doc.setCharacterAttributes(startOffset, endOfQuote - startOffset + 1, quote, false);
                        //String token = content.substring(startOffset, endOfQuote + 1);
                        //System.out.println( "quote: " + token );
               return endOfQuote + 1;
          private int getOtherToken(String content, int startOffset, int endOffset)
             int endOfToken = startOffset + 1;
               while ( endOfToken <= endOffset )
                    if ( isDelimiter( content.substring(endOfToken, endOfToken + 1) ) )
                         break;
                    endOfToken++;
               String token = content.substring(startOffset, endOfToken);
                        //System.out.println( "found: " + token );
               if ( isKeyword( token ) )
                    doc.setCharacterAttributes(startOffset, endOfToken - startOffset, keyword, false);
               if(isimpclasses1 ( token) )
                    doc.setCharacterAttributes(startOffset, endOfToken - startOffset, impclasses1, false);
               return endOfToken + 1;
}