Sample RxJava large file process line-by-line

lbl_rxjs.java

/**
 * Opens a file at a specified URL and returns a Flowable ready to emit
 * its contents line by line.
 *
 * @param filepath the file path to open
 * @return a stream ready to be consumed. Its output will be a file line on each emission.
 */
public Flowable<String> openFileAsStream(String filepath) {
    return Flowable.using(
            () -> new BufferedReader(new FileReader(filepath)),
            reader -> Flowable.fromIterable(() -> reader.lines().iterator()),
            BufferedReader::close
    );
}
openFileAsStream(filePath)
      .parallel(4)
      .runOn(Schedulers.io())
      .map(this::processFileLineForOperations)
      .sequential()
      .buffer(100)
      .onBackpressureBuffer(backPressureBufferSize)