Java Demo Code

DirectoryCollector.java

public class DirectoryCollector implements Collector {

    private final PlainFileFilter fileFilter;

    public DirectoryCollector(PlainFileFilter ff) {
        fileFilter = ff;
    }

    @Override
    public List<FileData> collect(Path path) {
        List<FileData> data = new ArrayList<>();

        try (DirectoryStream<Path> ds = Files.newDirectoryStream(path)) {
            for (Path p : ds) {
                if (Files.isDirectory(p, LinkOption.NOFOLLOW_LINKS)) {
                    data.addAll(new DirectoryCollector(fileFilter).collect(p));
                } else {
                    if (fileFilter.accept(p.toFile())) {
                        data.addAll(new FileCollector().collect(p));
                    }
                }
            }
        } catch (IOException ex) {
            System.err.println(ex.getMessage());
        }
        return data;
    }
}