Java Swing DocumentFilter create custom filter

import javax.swing.JFrame;
import javax.swing.JTextField;
import javax.swing.text.AbstractDocument;
import javax.swing.text.AttributeSet;
import javax.swing.text.BadLocationException;
import javax.swing.text.Document;
import javax.swing.text.DocumentFilter;

class My extends DocumentFilter {
   public void insertString(DocumentFilter.FilterBypass fb, int offset, String string, AttributeSet attr)
         throws BadLocationException {
      System.out.println("insert string" + string);
      System.out.println(offset);
      super.insertString(fb, offset, string, attr);
   }/*  w  ww .  ja va 2  s  .  co m*/

   public void remove(DocumentFilter.FilterBypass fb, int offset, int length) throws BadLocationException {
      System.out.println("remove");

      super.remove(fb, offset, length);
   }

   public void replace(DocumentFilter.FilterBypass fb, int offset, int length, String text, AttributeSet attrs)
         throws BadLocationException {
      System.out.println("replace");
      super.replace(fb, offset, length, text, attrs);
   }
}

public class Main {
   public static void main(String args[]) {
      JFrame frame = new JFrame("Example");
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

      JTextField textFieldOne = new JTextField();
      Document textDocOne = textFieldOne.getDocument();
      DocumentFilter filterOne = new My();
      
      ((AbstractDocument) textDocOne).setDocumentFilter(filterOne);
      
      frame.add(textFieldOne);

      frame.setSize(250, 150);
      frame.setVisible(true);
   }
}