Ciao a tuttii

Sono ancora fermo al mio problema dopo numerosi tentativi...

Ho creato questa cosa:

codice:
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.awt.*;

import javax.swing.*;

public class ProvaGUI extends JPanel implements ActionListener {
	
    protected JPanel botton, panel1, panel2;
    
    public ProvaGUI(){
    	
    	setLayout(new BorderLayout());
    	
    	panel1 = new JPanel();
    	panel2 = new JPanel();
    	
    	botton = new JPanel();
    	
    	JButton b1 = new JButton("Bottone 1");
    	JButton b2 = new JButton("Bottone 2");
    	JButton a1 = new JButton("Abilita 1");
    	JButton a2 = new JButton("Abilita 2");
    	
    	
    	panel1.add(b1);
    	panel2.add(b2);
    	
    	
    	botton.add(a1);
    	a1.setMnemonic(KeyEvent.VK_D);
    	a1.setActionCommand("vPanel1");
    	botton.add(a2);
    	a2.setMnemonic(KeyEvent.VK_D);
    	a2.setActionCommand("vPanel2");
    	
    	a1.addActionListener(this);
    	a2.addActionListener(this);

    	add(botton, BorderLayout.PAGE_START);
    	add(panel1, BorderLayout.CENTER);
    	panel1.setVisible(false);
    	add(panel2, BorderLayout.CENTER);
    	panel2.setVisible(false);
    	
    }
	
	public void actionPerformed(ActionEvent e) {
		
		if("vPanel1".equals(e.getActionCommand())){
			panel1.setVisible(true);
			panel2.setVisible(false);
			
		}else{
			panel1.setVisible(false);
			panel2.setVisible(true);			
		}		     
    }
	
    
    private static void createAndShowGUI() {

        //Create and set up the window.
        JFrame frame = new JFrame("ButtonDemo");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        //Create and set up the content pane.
        ProvaGUI prova = new ProvaGUI();
        frame.getContentPane().add(prova);

        //Display the window.
        frame.pack();
        frame.setVisible(true);
    }
    
    public static void main(String[] args) {
        //Schedule a job for the event-dispatching thread:
        //creating and showing this application's GUI.
        javax.swing.SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                createAndShowGUI(); 
            }
        });
    }

}
Che dovrebbe fare questa cosa:

premendo su a1 dovrebbe abilitare il panel1

premendo su a2 dovrebbe abilitare il panel2

Solo che abilita solamente il panel2 alla pressione di a2.

Dove commetto l'errore??

Grazie mille!

mainetz.