Dynamically adding JLabel to my GUI

[Renxx]

import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.ArrayList;
import java.util.Random;

import javax.swing.Icon;
import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPasswordField;
import javax.swing.JTextField;


public class a62JButton {

   /**
    * @param args
    */
   public static void main(String[] args) {
      GUI go = new GUI();
      go.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      go.setSize(300, 300);
      go.setVisible(true);
   }

}

class Generate {
   
  Random gen = new Random(); 
  private int number;
 
  public int getNumber() {
     number = gen.nextInt(6);
     return number;
  }
  
}

class GUI extends JFrame {
   
   private JButton reg;
   private JButton cus;
   private JTextField tField;
   private JPasswordField pField;
   
   GUI() {
      super("The title");
      setLayout(new FlowLayout());
      
      reg = new JButton("Regular");
      add(reg);
      
    //  Icon b = new ImageIcon(getClass().getResource("a.png"));
      cus = new JButton("Custom");
     // cus.setRolloverIcon(null);
      add(cus);
      
      tField = new JTextField("Input");
      tField.setEditable(true);
      add(tField);
      
      
      HandlerClass handler = new HandlerClass();
      reg.addActionListener(handler);
      cus.addActionListener(handler);
   }
   
   private class HandlerClass implements ActionListener {
    //  ArrayList<JLabel> al = new ArrayList<JLabel>();
      Generate obj = new Generate();
      private int muutuja;
      
      public void actionPerformed(ActionEvent e) {
         if(e.getSource()==reg) {
            muutuja = obj.getNumber();
            JOptionPane.showMessageDialog(null, "Generated random number "+ muutuja);
              [B] add(new JLabel(Integer.toString(muutuja)));[/B]
         } else if(e.getSource()==cus) {
            if(tField.isEditable()) {
               tField.setEditable(false);            
            } else {
               tField.setEditable(true);
            }
         }
      }
      
   }
}

I made a program with GUI. When you run the program and click on the JButton, then it generates Random number, but how can I add another JLabel to GUI which displays the generated number while the program is running. I bolded the line which shows the problem line. I can't get added that line to in main class created go object which is a GUI.

[al_Marshy_1981]

call validate() after you add the JLabel

Container.validate() (Java Platform SE 6)

[Renxx]

Thank you ;)