files-matches-test.java

public String get(String filename) throws IOException {
        Path root = Paths.get("data");
        Stream<Path> other = Files.walk(root, 3).filter(path -> !path.equals(root)).map(root::relativize);

        List<Path> paths = (other.collect(Collectors.toList()));

        System.out.println(paths);

        for (Path path: paths)
            if (path.toString().matches("^[A-z\\/]*" + filename))
                return path.toString();
        return null;
}