#vulnerable code 
                                public static void main(String[] args)
    {
        String source = System.getProperty("source");
        String destination = System.getProperty("destination");
        
        if (source == null) {
            help();
            return;
        }
        int threads = getThreadsNumber();
        boolean removeDeprecatedNodes = getRemoveDeprecatedNodes();
        logger.info("Threads Number = " + threads);
        Reader reader = new Reader(source, threads);
        Node root = reader.read();
        
        Writer writer = new Writer(destination, root, removeDeprecatedNodes);
        writer.write();
    } 
                            #location 16 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                public static void main(String[] args) {
        Configuration cfg = parseLegacyConfiguration();
        if (cfg == null) {
            cfg = parseConfiguration(args);
        }
        if (cfg == null) {
            Options options = createOptions();
            printHelp(options);
            return;
        }
        String sourceAddress = cfg.source();
        String destinationAddress = cfg.target();
        int threads = cfg.workers();
        boolean removeDeprecatedNodes = !cfg.copyOnly();
        LOGGER.info("using " + threads + " concurrent workers to copy data");
        Reader reader = new Reader(sourceAddress, threads);
        Node root = reader.read();
        if (root != null) {
            Writer writer = new Writer(destinationAddress, root, removeDeprecatedNodes);
            writer.write();
        } else {
            LOGGER.error("FAILED");
        }
    }