How to stop scanning after I input a certain line?

Question

I want to build a program that only stops scanning for strings until after I input "0" in the console, how do I do that?

I assume I can use do while loop, but I don't know what to put in the while() condition.

    Scanner scan = new Scanner(System.in);

    do {

        String line = scan.nextLine(); 

        //do stuff

    } while(); //what do i put in here to stop scanning after i input "0"

Thanks in advance, I'm new to Java and OOP in general.

Put in there some condition ot check if `line` is different from "0". You need to declare the variable outside of the loop tho. — Amongalen, Mar 20 '20 at 12:12
Does this answer your question? [How do I exit a while loop in Java?](https://stackoverflow.com/questions/7951690/how-do-i-exit-a-while-loop-in-java) — steviestickman, Mar 20 '20 at 12:13
Does this answer your question? [How to end a while Loop via user input](https://stackoverflow.com/questions/18975208/how-to-end-a-while-loop-via-user-input) — Joshua Wade, Mar 20 '20 at 15:35

Jason · Answer 1 · 2020-03-20T12:25:30.367

1

You can use a while loop instead of a do-while loop. Define a String that will be initialized inside the while loop. On each iteration we assign the String to Scanner#nextLine and check if that line is not equal to 0. If it is, the while-loop prevents iteration.

        Scanner scan = new Scanner(System.in);

        String line;

        while (!(line = scan.nextLine()).equals("0")) {
            System.out.println("line: " + line);
        }

edited Mar 20 '20 at 12:25

answered Mar 20 '20 at 12:14

Jason

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nextLine() still takes 0 – Abhinav Chauhan Mar 20 '20 at 12:22
i think he want to enter input until 0 is pressed , so your code still let the zero enter , because , nextLine() will take entire line, doesn't matter what condition you appy, please see my answer – Abhinav Chauhan Mar 20 '20 at 12:29
Eh, he said **until after I input 0** which means at some point he expects to input 0. This will allow him to process that input until 0 is provided. – Jason Mar 20 '20 at 12:41
so did i get it incorrect, i still don't get it, he didn't provide an example, i answered according to what i understood – Abhinav Chauhan Mar 20 '20 at 12:43
Yea, I would presume that it's a matter of misunderstanding the question. – Jason Mar 20 '20 at 12:45
let me ask for an example from OP – Abhinav Chauhan Mar 20 '20 at 12:45
Absolutely, it's always a good idea to ask for clarity. I could be wrong. – Jason Mar 20 '20 at 12:46
I figured it out by just using if(line.equals("0")) break; statement inside the while loops, for some reason your '!' is not working on me – AB3 Mar 20 '20 at 14:17

score 1 · Answer 2 · answered Mar 20 '20 at 12:28

1

You don't have to use any loop , as you said you want to stop input when 0 is pressed by default for nextLine() the input stops when user press the enter key because it is the delimiter , so just change the delimiter

Scanner scanner = new Scanner(System.in);
scanner.useDelimiter("0");   //regex
String s = scanner.next(); // no matter what user enters the s will contain the input before 0

answered Mar 20 '20 at 12:28

Abhinav Chauhan

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The user said **until I stop scanning for Strings** so it is implied they want multiple String values, meaning some type of looping mechanics is required. Not a singular line. – Jason Mar 20 '20 at 12:43

How to stop scanning after I input a certain line?

2 Answers2