TextField Document listener

Question

Hello, I have a JTextField and I have created a DocumentListener because I don't want to allow user to insert too many characters.
When he does, I get this exception "Attempt to mutate in notification". Could anyone help me? My code is this one:
    public class MyListener implements DocumentListener
        public void insertUpdate(DocumentEvent ev)
            Document doc=(Document)ev.getDocument();           
            if(isTooLong()==true)
                try
                    doc.remove(ev.getOffset(),ev.getLength());
                catch(Exception e)
                    System.out.println("Error " + e.getMessage());
                    System.exit(0);
        public void removeUpdate(DocumentEvent e)
        public void changedUpdate(DocumentEvent e) {
    }

Answer 1

I get this exception "Attempt to mutate in notification". You can't update the Document from a DocumentListener.
The latest recommendation on how to do this is to use a DocumentFilter. An exaple can be found in the Swing tutorial on "Using Text Components":
http://java.sun.com/docs/books/tutorial/uiswing/components/generaltext.html