Attempt to mutate in notification error

Question

I have a text editor, i want to make this
when i man type double /, che color of the text from position 0 to position 10 become blue
I write code like this
import java.awt.*;
import java.awt.event.*;
import java.util.Hashtable;
import javax.swing.*;
import javax.swing.text.*;
import javax.swing.event.*;
public class TextComponentDemo extends JFrame {
JTextPane textPane;
DefaultStyledDocument dsd;
Hashtable actions;
SimpleAttributeSet attrs;
Style style;
public TextComponentDemo() {
//Create the document for the text area.
dsd = new DefaultStyledDocument();
//Create the text pane and configure it.
textPane = new JTextPane(dsd);
attrs = new SimpleAttributeSet();
StyleConstants.setForeground(attrs, Color.blue);
dsd.addDocumentListener(new MyDocumentListener());
//And this one listens for any changes to the document.
protected class MyDocumentListener
implements DocumentListener, ChangeListener {
public void insertUpdate(DocumentEvent e) {
     if (sel.compareTo("//") == 0) {
     dsd.setCharacterAttributes(0,10, attrs, true);
but i have this exception at line
dsd.setCharacterAttributes(0,10, attrs, true);
Can't take the textjava.lang.IllegalStateException: Attempt to mutate in notification
how i can resolve this exception?

Answer 1

thx
you know where i can file an example that when i press
the program show a windows with the list of java method, like this
JFrame jf = new JFrame();
jf.
setSize()
setBound()
setTitle()
getPosition()
ecc...