How to read all files in directory iteratively in Java?

Question

I have a directory on network drive with million of files. If I try to read it with

folder.listFiles()

it will take a lot of time until resulting array will be filled with files.

I would like to receive files by one and printout a progress.

How can I do this in Java?

Answer 1

You might try with DirectoryStream :

Path dir = Paths.get("C:\\"); // directory to list

try (DirectoryStream<Path> stream = Files.newDirectoryStream(dir)) {
    for (Path entry: stream) {
        System.out.println(entry);
    }
} catch (DirectoryIteratorException ex) {
    ex.printStackTrace();
} catch (IOException ex) {
    ex.printStackTrace();
}

You can also make the DirectoryStream filter files for you if you need to: all you need to do is add a parameter to the Files.newDirectoryStream call:

DirectoryStream<Path> stream = Files.newDirectoryStream(dir, "*.{txt,png,jpg}");

Answer 2

You can use the NIO.2 API:

try (DirectoryStream<Path> directoryStream = Files.newDirectoryStream(Paths.get("/path/to/directory"))) {
    for (Path path : directoryStream) {
        System.out.println(path.toString());
    }
} catch (IOException ex) {}