public static Collection<File> getTMXFiles(File directory) {
        if (!directory.isDirectory()) return Collections.emptyList();

        List<File> ret = new Vector<File>();

        for (File f : directory.listFiles()) {
            if (f.isDirectory()) {
                ret.addAll(getTMXFiles(f));
            } else if (isTMX(f)) {
                ret.add(f);
            }
        }

        return ret;
    }