Criar novo container HELP

void Memoria1()  //6x6//
      {
      painel = new Painel(); //cria um novo painel
      this.getContentPane().add(painel); //adiciona esse panel no frame atual
      this.setTitle(" Memória 2004"); //seta o title o frame atual
      this.setSize(800,600); // seta o tamanho do frame atual
      this.show();
      }

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;


public class Memoria extends JFrame
{

   JPanel painel2;
   JPanel painel1;
   JPanel painel;
   private JButton but1,but2,but3;
   private JLabel texto;
   private JPanel painel5,painel6;
   Memoria()
   {

      but1=new JButton("Fácil - 4x4 ");
      but2=new JButton("Médio - 6x6");
      but3=new JButton("Difícil - 8x8");
      texto =new JLabel("Escolha a dificuldade");

      painel5 =new JPanel();
      painel5.add(but1);
      painel5.add(but2);
      painel5.add(but3);
      painel5.add(texto);
      getContentPane().add(painel5);
      this.setSize(500,100);

       but1.addActionListener(
            new ActionListener()
               {
               public void actionPerformed(ActionEvent e)
                  {
                      new Memoria3();
                  }
               } );
      but2.addActionListener(
                  new ActionListener()
                     {
                     public void actionPerformed(ActionEvent e)
                        {
                        new Memoria1();
                        }
                     } );
      but3.addActionListener(
                  new ActionListener()
                     {
                     public void actionPerformed(ActionEvent e)
                        {
                         Memoria2 mem = new Memoria2();
                        }
                     } );

              this.show();

   }


   public static void main(String[] args)
   {
      new Memoria();
   }
}


class Memoria1 extends JFrame
{

      void Memoria1()  //6x6//
      {
      JPanel painel = new JPanel();
      this.getContentPane().add(painel);
      this.setTitle(" Memória 2004");
      this.setSize(800,600);
      this.show();
      }
}

class Memoria2 extends JFrame
{

      void Memoria2()//8x8//
      {
         this.setTitle(" Memória 2004");
         this.setSize(1000,600);

         JPanel painel1 = new JPanel();

         this.getContentPane().add(painel1);
         this.show();
      }
}

class Memoria3 extends JFrame
{

   void Memoria3()//4x4//
      {
         this.setTitle("Memoria 2004");
         this.setSize(800,600);

         JPanel painel2 = new JPanel();

         this.getContentPane().add(painel2);
         this.show();
      }
}