How do I close a JFrame ???

Hi Experts,

   In the end following code, every time when the gameOver() is called, it creates a new Test(). Therefore, after several runs ... I got many Test() and many JFrame .... How do I close the previous one after a new one is created ??? many thanks !!!


public class Test extends JFrame implements KeyListener, ActionListener{
           
         // --- blah blah ....
 
          public Test() {

         // --- blah blah ....                      
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setSize(425,425) ;
        show() ;
       
    }
    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        Test mySnake = new Test() ;
       
    }
   
    public void actionPerformed(ActionEvent e) {
               blah .....    
         if(e.getSource() == restart){ Test PlayAgain = new Test() ;}
               blah .....
   }

      public void gameOver(){
           //   blah ....  
        restart = new JButton() ;
        restart.setText("Play Again!") ;
        restart.setSize(150,30) ;
        restart.setLocation(125,150) ;
        restart.addActionListener(this) ;
        getContentPane().add(restart) ;
          // blah ...
       }
}