When implementing visual effects with Swing
it's often necessary to paint a component to an off-screen buffer

unfortunately it causes problems if this component or any of its children 
are double-buffered

Run the following test and see the unexpected visual artefacts

JDK 6u10 or previous version

import javax.swing.*;
import java.awt.*;
import java.awt.image.BufferedImage;

public class Test {

    private static void createGui() {
        final JFrame frame = new JFrame();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        
        // panel is double buffered
        final JPanel panel = new JPanel();
        panel.setSize(100, 100);

        JButton b = new JButton("Test") {

            protected void paintComponent(Graphics g) {
                super.paintComponent(g);

                // Note - the panel is not added to the frame
                BufferedImage im = new BufferedImage(100, 100, BufferedImage.TYPE_INT_ARGB);
                panel.paint(im.getGraphics());
            }
        };
        frame.add(b);

        frame.setSize(200, 200);
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }

    public static void main(String[] args) throws Exception {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                Test.createGui();
            }
        });
    }
}