Can't synchronize multiple JPanels in a JFrame

[vassil_zorev]

Hello,
I've recently started using swing for creating User Interfaces and here is a difficulty I cannot overcome. My application has a main class and four JPanel forms.
The main class has a function that creates a JFrame and loads in it an instance of the first "JPanel" class. This has three radio buttons in a group and a JButton with the below function:

Code:

private void jButton1MouseClicked(java.awt.event.MouseEvent evt) {                                      
// TODO add your handling code here:
        if (jRadioButton1.isSelected()) {
            JOptionPane.showMessageDialog(null, "Beginner");
            this.selection = 1;
        } else  if (jRadioButton2.isSelected()) {
            JOptionPane.showMessageDialog(null, "Intermediate");
            this.selection = 2;
        } else  if (jRadioButton3.isSelected()) {
            JOptionPane.showMessageDialog(null, "Advanced");
            this.selection = 3;
        } else  {
            JOptionPane.showMessageDialog(null, "Make a selection!");
        }
    }

selection is a public int member of NewJPanel (fst JPanel class)

Here is the Main class:

Code:

public Main() {
        
    }
    
    public void PlayAGame() {
        JFrame myFrame = new JFrame("Difficulty selection:");
        NewJPanel panel = new NewJPanel();
        myFrame.setSize(256,256);
        myFrame.setDefaultCloseOperation(myFrame.EXIT_ON_CLOSE);
        myFrame.getContentPane().add(panel);
        myFrame.pack();
        myFrame.setVisible(true);
        switch (panel.selection)    {
            case 1: {
                NewJPanel1 panel1 = new NewJPanel1();
                myFrame.getContentPane().remove(panel);
                myFrame.getContentPane().add(panel1);
                break;
            }
            case 2: {
                NewJPanel2 panel2 = new NewJPanel2();
                myFrame.getContentPane().remove(panel);
                myFrame.getContentPane().add(panel2);
                break;
            }
            case 3: {
                NewJPanel3 panel3 = new NewJPanel3();
                myFrame.getContentPane().remove(panel);
                myFrame.getContentPane().add(panel3);
                break;
            }
            default:    {
                break;
            }
        }
    }
    
    public static void main(String ar[]){
        Main myMain = new Main();
        myMain.PlayAGame();
    }

Here is what I want the code to do:
Load a NewJPanel in the frame, the user makes a choice and clicks the button, then PlayAGame() (using the switch) unloads the NewJPanel and loads the suitable Panel in the frame.

Here is what it does:
NewJPanel is loaded, I make a choice, click the button and nothing happens; NewJPanel is still in the frame

I need help, please!

Regards,
Vassil Zorev