Runtime Switching Between Look-And-Feels

Whenever the user of the application mouses over a different button, the entire application is updated in terms of its look and feel.

public class LAFSwitchButton extends JButton {
    public LAFSwitchButton(final String laf) {
        setText(laf);
        setPreferredSize(new Dimension(130,40));
        addMouseListener(new MouseAdapter() {
            @Override
            public void mouseEntered(MouseEvent e) {
                NbPreferences.forModule(LAFSwitchButton.class).put("laf", laf);
                setBorder(new LineBorder(Color.RED,2));
            }
            @Override
            public void mouseExited(MouseEvent e) {
                setBorder(new LineBorder(Color.BLACK));
            }
        });
    }
}

Now add a few of the above buttons to a TopComponent, get notified of preference changes, and then update the look and feel:

public final class LAFSwitchTopComponent extends TopComponent {
    public LAFSwitchTopComponent() {
        initComponents();
        setName(NbBundle.getMessage(LAFSwitchTopComponent.class, "CTL_PersonasTopComponent"));
        setToolTipText(NbBundle.getMessage(LAFSwitchTopComponent.class, "HINT_PersonasTopComponent"));
        setLayout(new MigLayout());
        add(new LAFSwitchButton("Nimbus"), "growx, push, wrap");
        add(new LAFSwitchButton("Metal"), "growx, push, wrap");
        add(new LAFSwitchButton("GTK"), "growx, push, wrap");
        add(new LAFSwitchButton("Motif"), "growx, push, wrap");
        final Preferences pref = NbPreferences.forModule(LAFSwitchButton.class);
        pref.addPreferenceChangeListener(new PreferenceChangeListener() {
            @Override
            public void preferenceChange(final PreferenceChangeEvent evt) {
                WindowManager.getDefault().invokeWhenUIReady(new Runnable() {
                    @Override
                    public void run() {
                        if (evt.getKey().equals("laf")) {
                            String laf = pref.get("laf", "");
                            if (laf.equals("Metal")) {
                                setLAF("javax.swing.plaf.metal.MetalLookAndFeel");
                            } else if (laf.equals("Nimbus")) {
                                setLAF("com.sun.java.swing.plaf.nimbus.NimbusLookAndFeel");
                            } else if (laf.equals("GTK")) {
                                setLAF("com.sun.java.swing.plaf.gtk.GTKLookAndFeel");
                            } else if (laf.equals("Motif")) {
                                setLAF("com.sun.java.swing.plaf.motif.MotifLookAndFeel");
                            }
                        }
                    }
                    private void setLAF(String laf) {
                        try {
                            UIManager.setLookAndFeel(laf);
                            JFrame frame = (JFrame) WindowManager.getDefault().getMainWindow();
                            SwingUtilities.updateComponentTreeUI(frame);
                        } catch (ClassNotFoundException ex) {
                            Exceptions.printStackTrace(ex);
                        } catch (InstantiationException ex) {
                            Exceptions.printStackTrace(ex);
                        } catch (IllegalAccessException ex) {
                            Exceptions.printStackTrace(ex);
                        } catch (UnsupportedLookAndFeelException ex) {
                            Exceptions.printStackTrace(ex);
                        }
                    }
                });
            }
        });
    }
    ...
    ...
    ...

That's all, and all of the above has always been possible, there's nothing new or 7.0-related in the code above; now mousing over one of the buttons will cause an immediate update of the look and feel of the application.