How to build a Java 8 stream from System.in / System.console()?

Question

Given a file, we can transform it into a stream of strings using, e.g.,

Stream lines = Files.lines(Paths.get(\"input.txt\"))

Answer 1

Usually the standard input is read line by line, so what you can do is store all the read line into a collection, and then create a Stream that operates on it.

For example:

List<String> allReadLines = new ArrayList<String>();

BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
String s;
while ((s = in.readLine()) != null && s.length() != 0) {
    allReadLines.add(s);
}

Stream<String> stream = allReadLines.stream();

Answer 2

you can use just Scanner in combination with Stream::generate:

Scanner in = new Scanner(System.in);
List<String> input = Stream.generate(in::next)
                           .limit(numberOfLinesToBeRead)
                           .collect(Collectors.toList());

or (to avoid NoSuchElementException if user terminates before limit is reached):

Iterable<String> it = () -> new Scanner(System.in);

List<String> input = StreamSupport.stream(it.spliterator(), false)
            .limit(numberOfLinesToBeRead)
            .collect(Collectors.toList());

Answer 3

A compilation of kocko's answer and Holger's comment:

BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
Stream<String> stream = in.lines().limit(numberOfLinesToBeRead);