How to let user download zip file using vaadin file downloader

I've followed this topic and it perfectly works. Here's the function to create resource for file downloader

 private StreamResource createResource() {
    return new StreamResource(new StreamSource() {
        @Override
        public InputStream getStream() {
            String text = "My image";

            BufferedImage bi = new BufferedImage(100, 30, BufferedImage.TYPE_3BYTE_BGR);
            bi.getGraphics().drawChars(text.toCharArray(), 0, text.length(), 10, 20);

            try {
                ByteArrayOutputStream bos = new ByteArrayOutputStream();
                ImageIO.write(bi, "png", bos);
                return new ByteArrayInputStream(bos.toByteArray());
            } catch (IOException e) {
                e.printStackTrace();
                return null;
            }

        }
    }, "myImage.png");
}

but i don't know how to make it create a resource of zip file. Do i need to create many resources?. Thank you

Here's the solution that i figured out myself

private StreamResource createZipResource()
{ 
    return new StreamResource(new StreamSource()
    { 
        @Override
        public InputStream getStream()
        {
            ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();

            try
            {
                ZipOutputStream out = new ZipOutputStream(byteArrayOutputStream);

                for (int i = 0; i < listData.size(); i++)
                {
                    if (listData.get(i).contains(".txt"))
                    { 
                        out.putNextEntry(new ZipEntry(listData.get(i) + ".txt"));
                    }
                    else
                    {
                        out.write(listData.get(i).getBytes());                            
                    } 
                }
                out.close();
                return new ByteArrayInputStream(byteArrayOutputStream.toByteArray()); 
            } 
            catch (IOException e)
            {
                System.out.println("Problem writing ZIP file: " + e);
            }
            return null; 
        }
    },"Filename.zip"); 
}