Recursively list files in Java

Question

How do I recursively list all files under a directory in Java? Does the framework provide any utility?

I saw a lot of hacky implementations. But none from the fra

Answer 1

base on @Michael answer, add check whether listFiles return null

static Stream files(File file) {
    return file.isDirectory()
            ? Optional.ofNullable(file.listFiles()).map(Stream::of).orElseGet(Stream::empty).flatMap(MainActivity::files)
            : Stream.of(file);
}

or use Lightweight-Stream-API, which support Android5 & Android6

static Stream files(File f) {
    return f.isDirectory() ? Stream.ofNullable(f.listFiles()).flatMap(MainActivity::files) : Stream.of(f);
}