public void saveComponentAsJPEG(Component myComponent, String filename) {
        Dimension size = myComponent.getSize();
        BufferedImage myImage = new BufferedImage(size.width, size.height, BufferedImage.TYPE_INT_RGB);
        Graphics2D g2 = myImage.createGraphics();
        myComponent.paint(g2);
        try {
            OutputStream out = new FileOutputStream(filename);
            ImageIO.write(myImage, "jpg", out);
            out.close();
        } catch (Exception e) {
        }
    }

saveComponentAsJPEG(dialog, file);

saveComponentAsJPEG(dialog.getContentPane(), file);