public static boolean isFileURL(URL url) {
        String protocol = url.getProtocol();
        return (URL_PROTOCOL_FILE.equals(protocol));
    }
Determine whether the given URL points to a resource in the file system,
that is, has protocol "file" or "vfs".

@param url the URL to check
@return whether the URL has been identified as a file system URL
src/main/java/spark/utils/ResourceUtils.java