Continuação do timer, mesmo fechando a janela

public class tempo4 extends javax.swing.JFrame {
    DateFormat dateFormat;      
    Calendar calendar;       
    Timer timer; 
    boolean janela = true;
    /** Creates new form tempo4 */
    public tempo4() {
        this.dateFormat = new SimpleDateFormat("HH:mm:ss");   
        this.calendar = Calendar.getInstance();   
        this.calendar.set(Calendar.MILLISECOND, 0);   
        this.calendar.set(Calendar.SECOND, 0);   
        this.calendar.set(Calendar.MINUTE, 0);   
        this.calendar.set(Calendar.HOUR_OF_DAY, 0);                     
        this.initialize(); 
        initComponents();
    }
    protected void initialize() {   
        this.add(this.getLabel());    
        this.go();   
    }   
  
    public JLabel getLabel() {   
        if (this.jLabel1 == null) {   
            this.jLabel1 = new JLabel(getTime());   
            //this.label.setPreferredSize(new Dimension(100, 22));   
        }   
        return this.jLabel1;   
    }
    
    public void go() {   
        ActionListener action = new ActionListener() {   
            public void actionPerformed(ActionEvent e) {   
                jLabel1.setText(getTime());   
            }
        };   
        this.timer = new Timer(1000, action);   
        this.timer.start();   
    }   
  
    public String getTime() {   
        this.calendar.add(Calendar.SECOND, 1);   
        return this.dateFormat.format(this.calendar.getTime());   
    }   
 
   //aqui estao os botoes "start", "stop" e "janela", respectivamente...
     
    private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         
        // TODO add your handling code here:
        if (!timer.isRunning()) {   
            timer.start();          
    }
    }                                        

    private void jButton2ActionPerformed(java.awt.event.ActionEvent evt) {                                         
        // TODO add your handling code here:
        if (timer.isRunning()) {   
            timer.stop();   
         } 
    }                                        

    private void jButton3ActionPerformed(java.awt.event.ActionEvent evt) {                                         
        // TODO add your handling code here:
        this.dispose();
        JOptionPane.showMessageDialog(null, "Você irá para a próxima janela!");
        new tempo4().setVisible(true);
    }