How to obtain Inputstream from Java 8 Streams?

Question

I have some data streamed from different files. It is in the following format:

Stream<String> linesModifiedAndAppendedFromVariousFiles=getLines();

However, I need to feed this into an library method that accepts InputStream or Reader as a parameter.

How can I feed this Java 8 stream into an InputStream or a type of Reader?

P.S: this is not about wrapping java.util.streams.Stream around an InputStream. What I am looking for is the other way around.

Answer 1

You can do this with PipedReader and PipedWriter.

PipedReader reader = new PipedReader();

Runnable feeder = new Runnable() {
    @Override
    public void run() {
        try (PipedWriter writer = new PipedWriter(reader)) {
            linesModifiedAndAppendedFromVariousFiles.forEachOrdered(line -> {
                try {
                    writer.write(line);
                    writer.write('\n');
                } catch (IOException e) {
                    throw new UncheckedIOException(e);
                }
            });
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }
};
new Thread(feeder).start();

someLibraryMethod.consumeReader(reader);