Create Zip file in memory !

I find myself writing and rewriting this piece of code whenever I want to zip a set of files (in memory) and return the zipped file back as an object in memory. I often use this when the user requests a download of multiple reports and the deployment environment doesn't allow for disk access.

I thought I'd post it here so that I could copy-paste it the next time I need it :) If you've stumbled upon this page, you're free to use the code below too!

private static byte[] createZip(Map files) throws IOException
    {
        ByteArrayOutputStream bos = new ByteArrayOutputStream();
        ZipOutputStream zipfile = new ZipOutputStream(bos);
        Iterator i = files.keySet().iterator();
        String fileName = null;
        ZipEntry zipentry = null;
        while (i.hasNext())
        {
            fileName = (String) i.next();
            zipentry = new ZipEntry(fileName);
            zipfile.putNextEntry(zipentry);
            zipfile.write((byte[]) files.get(fileName));
        }
        zipfile.close();

        return bos.toByteArray();
    }