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

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

Stream<String> lines = Files.lines(Paths.get("input.txt"))

Can we build a stream of lines from the standard input in a similar way?

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);

Java Read Console Input, Reading console input in programs may be necessary to make applications To read console input, we shall wrap the System.in (standard input stream) in an� The Java.io.Console class provides methods to access the character-based console device, if any, associated with the current Java virtual machine. The Console class was added to java.io by JDK 6. Important Points: It is used to read from and write to the console, if one exists.

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());

Console (Java Platform SE 8 ), How to build a Java 8 stream from System.in / System.console()?. 由怎甘沉沦 提交于2019-11-30 11:49:00. Given a file, we can transform it into a stream of� 3- System.console. This is the modern way of reading input from console in Java, it’s introduced in JDK 1.6 and allows developers to read input without using System.in. The drawback of using this technique is that it doesn’t work under IDE and only works in interactive environments.

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();

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Comments
  • See also stackoverflow.com/questions/29611661/…
  • This throws a NoSuchElementException if the stream ends before the limit (e.g. with Ctrl/Cmd+D).
  • @AjahnCharles fixed
  • If you have a BufferedReader there is no need for storing the lines into a Collection to get a Stream. The bigger problem is that interactive consoles usually don’t have an end-of-file…
  • Nice one. Didn't know this newly introduces method. Thanks, @Holger. :)
  • Great, BufferedReader.lines will eliminate much of the verbosity in this answer. If the numer of lines to be read is known, then in.limit(numberOfLines) should work here
  • "interactive consoles usually don’t have an end-of-file…" Don't you get an end-of-file when the program terminates? :-P
  • @Lii: no, a terminated program will not receive an end-of-file as a terminated program can’t receive anything.