POLYMORHISM FROM ABOUT PAGE

private void jMenu2MousePressed(java.awt.event.MouseEvent evt) {                                    
    about s = new about();
    s.setVisible(true);
    this.setVisible(false);
}                                   

private void jMenu3MousePressed(java.awt.event.MouseEvent evt) {                                    
    service d = new service();
    d.setVisible(true);
    this.setVisible(false);
}