Why is my Button failing to perform in my GUI?

My code below does not respond and open the plain message when I click the button after running it, I've checked the code a few times and can't see where I'm going wrong, can anyone see if there's something I missed as I think it should all be implemented correctly but the JButton is not opening my menu items. Many thanks

public static void main(String[] args) {
    // TODO Auto-generated method stub
    final JFrame frame=new JFrame("CoinSorterGUI");
    
    class MyItemListener implements ItemListener{
        
        public void itemStateChanged(ItemEvent ev) {
            boolean selected = (ev.getStateChange()== ItemEvent.SELECTED);
            AbstractButton button =(AbstractButton) ev.getItemSelectable();
            String command = button.getActionCommand();
            if (selected) {
                int messageType = -1;
                String message = "";
                if (command.equals("CoinCalculator")) {
                    messageType = JOptionPane.PLAIN_MESSAGE;
                    message = "Welcome to the CoinCalculator, click OK to begin program";
            }else if (command.equals("Multiple CoinCalculator")) {
                    messageType = JOptionPane.PLAIN_MESSAGE;
                    message = "Welcome to the Multiple CoinCalculator, click OK to begin program";
            }else if (command.equals("Print Coin List")) {
                    messageType = JOptionPane.PLAIN_MESSAGE;
                    message = "Current coin denominations are; £2, £1, 50p, 20p and 10p";
            }else if (command.equals("Set details")) {
                messageType = JOptionPane.INFORMATION_MESSAGE;
                message = " ** Set details Sub Menu ** "
                        + "    1 -  Set Currency       "
                        + "    2 -  Set minimum input value"
                        + "    3 -  Set Maximum input value"
                        + "    4 -  Return to main menu";
            }else if (command.equals("Display program configurations")) {
                messageType = JOptionPane.PLAIN_MESSAGE;
                message = "The current currency is £, the minimum input value is 0 and the maximum input value is 10000";
            }
                JOptionPane.showMessageDialog(frame,
                        message,
                        "CoinSorter",
                        messageType);
            }
                    
          }
        }

        JButton r1 = new JButton("CoinCalculator");
        r1.setActionCommand("CoinCalculator");
 
        JButton r2 = new JButton("Multiple CoinCalculator");
        r2.setActionCommand("Multiple CoinCalculator");
 
        JButton r3 = new JButton("Print Coin List");
        r3.setActionCommand("Print Coin List");
 
        JButton r4 = new JButton("Set details");
        r4.setActionCommand("Set details");
        
        JButton r5 = new JButton("Display program configurations");
        r5.setActionCommand("Display program configurations");
    
        MyItemListener myItemListener = new MyItemListener();
        r1.addItemListener(myItemListener);
        r2.addItemListener(myItemListener);
        r3.addItemListener(myItemListener);
        r4.addItemListener(myItemListener);
        r5.addItemListener(myItemListener);
        
        final ButtonGroup group = new ButtonGroup();
        group.add(r1);
        group.add(r2);
        group.add(r3);
        group.add(r4);
        group.add(r5);
        
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(700, 500);
        Container cont = frame.getContentPane();
 
        cont.setLayout(new GridLayout(0, 1));
        cont.add(new JLabel("Welcome to the CoinSorter, please choose from the options: "));
        cont.add(r1);
        cont.add(r2);
        cont.add(r3);
        cont.add(r4);
        cont.add(r5);
 
        frame.setVisible(true);

}

}