How to recieve System.in from standar io

[small oak]

So I wanna read input from standard input and I'm using Scanner.

private static String readInput(Scanner input) throws java.io.IOException {
        String line = null;
        try {
            while (input.hasNextLine()) {
                 line = input.nextLine();
            }
            input.close();

        } catch (Exception ex) {
            ex.printStackTrace();
        }
        System.out.println(line);
        return line;
    }```
But this is not exactly achiving my goal. I wanna read few/multiple lines of sentences. Then I wanna work with this but this only reads line by line so that is the problem. Obviously I will implement a stringbuilder but the problem I am having rn is I don't how or when to terminate. If I was reading a file then I will read until there are no more lines but what do I do here?

[rugged tinsel]

Detected code, here are some useful tools:

Formatted code

private static String readInput(Scanner input) throws java.io.IOException {
  String line = null ;
  try {
    while (input.hasNextLine()) {
      line = input.nextLine();
    }
    input.close();
  } catch (Exception ex) {
    ex.printStackTrace();
  }
  System.out.println(line);
  return line;
}

<@&987246399047479336> please have a look, thanks.

[frosty relic]

ur approach looks flawed for a few reasons. could u step back and explain what u want to achieve in detail please?

then we can tell u how to do it in a better way 👍

[small oak]

I wanna read input from standard io. You are allowed to have \n, meaning new lines and you can copy and paste a file in the System.in. Then I wanna read line by line and put everything in a string.

[frosty relic]

and how are u planning the user to indicate the end?

by closing the input (permanently - ctrl+c)?

[small oak]

that I have no idea. I have hidden test cases and intially I made my program to read a file so there wasn't any problem but now I have no clue what should signal the end. What is the most usual wya?

[small oak]

maybe

[frosty relic]

is this an assignment?

[small oak]

yes

[frosty relic]

could u share the full assignment description please

[small oak]

It is way to long (like multiple pages). Since this isn't even important part of the assigment it only says: "The input is provided on standard input (System.in in Java)."

[frosty relic]

i need to know more about it though

for example if there will be other input as well after or before that, or if it will be used with console pipping or not and more

easiest would be to see the full assignment

[small oak]

I'm making a parser for a language and I am reading a text file which I will make syntax tree for

[frosty relic]

there are many ways to approach it and i cant tell u the appropriate if ur holding back the stuff im asking u to share

[small oak]

tell me exactly what you wanna know and I will provide that.

This is literally the only thing about input in my assigment. It is so unimportant for this assignment that our prof said we could use online code as long as we give credit in the report.

[frosty relic]

it will take much longer for me to pull the stuff out of ur nose than u just sharing the file. or is there any reason u dont just drag drop it?

[small oak]

it is not in english

[rugged tinsel]

I uploaded your attachments as Gist.

[small oak]

this is a quick translation

[frosty relic]

this cant be the full thing, can it? its missing what u shared previously about System.in

anyways, this back and forth took too long for me. im out of time, cheers

[small oak]

some of the things are pictures, can't really copy and paste them.

but let me double check

[small oak]

Okay I checked google translate has word limits lol forgot that

You may assume that if the given program is syntactically correct, all numbers that are unlimited in the language definition (distance parameters and repetition parameters) will be at most M, and the total number of instructions executed when the program runs will be at most N (these are guarantees on the input, nothing you need to check).

The input file is at most M MB in size.

Output
If the given Leona program is syntactically incorrect, the following message should be printed, where X is the line on which the (first) syntax error occurs:

Syntax error on line X
See clarifications in the example cases below for which line is considered to be the line of the first syntax error.

Otherwise, if the given program is syntactically correct, a list of line segments drawn by the program should be output. The segments should be output in the same order as they are drawn by Leona, and each segment should be output on a new line, in the following format:

Here is COLOR the color of the line segment (in hex format just like in the language), START is the starting point of the line segment (the point where Leona started when the segment was drawn), and END is the ending point of the line segment (the point where Leona stopped). The coordinates should be accurate up to an error of EPS (if double variables are used and printed with 4 or more decimal places, this should not cause any issues).```

[rugged tinsel]

Detected code, here are some useful tools:

[small oak]

@frosty relic here is the remaining part

[violet dagger]

@small oak the problem is that we don't know when we should stop reading from system.in

[small oak]

That is exactly my problem as well. But is there maybe something I am just not seeing? A way around it.

[violet dagger]

No, you can't just say it will stop when it will stop

You have to know when it will stop

[frosty relic]

it depends. for example u can use EOF when the input is supposed to be piped

java Foo < input.txt

[violet dagger]

Or read a specific word, etc

But in any case, there is no generic solution

[frosty relic]

or when the user is supposed to close the connection by using ctrl+c

it depends on what the assignment envisions for the interaction

and how its automated tests work