Java8 Stream of files, how to control the closing of files?

Question

Suppose I have a Java8 Stream and that I use that stream to map and such, how can I control the closing of the FileReader

Answer 1

I know this is an old question, but there is a very nice solution that I found here and I don't think it's on SO.

The java.nio.file offers methods that let you do this cleanly:

filenames.map(Paths::get)
    // Nicer alternative to File::exists
    .filter(Files::exists)
    // This will automatically close the stream after each file is done reading
    .flatMap(path -> {
        try {
            return Files.lines(path);
        } catch (IOException e) {
            // Seamlessly handles error opening file, no need for filtering
            return Stream.empty();
        }
    })
    .map(/* Do something with each line... */)