how to download and save transparent png file

Hi all,

I'm trying to download and to save a transparent png file.
I succeed to download and save it, but in losing the transparent
background!

My source code is:
String url = "http://..../test.png";
URLConnection connection = new URL(url).openConnection();
Image image =
Toolkit.getDefaultToolkit().createImage((ImageProducer)connection.getContent());
ImageIO.write(toBufferedImage(image), extension, new
File(filename).getCanonicalFile());

with the function:

     private BufferedImage toBufferedImage(Image image) {
         if( image instanceof BufferedImage ) {
             return ((BufferedImage)image);
         } else {
             image = new ImageIcon(image).getImage();
             BufferedImage bufferedImage = new
BufferedImage(image.getWidth(null), image.getHeight(null),
BufferedImage.TYPE_INT_RGB );
             Graphics g = bufferedImage.createGraphics();
             g.drawImage(image,0,0,null);
             g.dispose();
             return (bufferedImage);
         }
     }

If someone have an idea for me?

(Is it possible to download and to save the getcontent() directly to a
file without transform it into Image?)

Thanks

--
Alex