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Thread: Help With coding on Arraylists and Scanner

  1. #1
    Junior Member
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    Default Help With coding on Arraylists and Scanner

    Hi I'm new to learning java/programing and I'm trying to create a function with the scanner class that reads the next line and appends it to an array list however my code doesn't work the way I want it to:

    import java.util.ArrayList;
    import java.util.Scanner;
     
    public class arrayappendtest {
     
        public static void main(String[] args) {
     
            Scanner s = new Scanner(System.in);
            String tmp;
     
            ArrayList<String> sample = new ArrayList();
     
            while (s.hasNext()) {
                System.out.println("Enter something (type quit to quit): ");
                tmp = s.nextLine();
                if (tmp.equals("quit")){
                    break;
                } else{
                    sample.add(tmp);
                }
            }
            s.close();
            System.out.println(sample);
     
        }
    }

    when I run this block there is always an extra entry


    test // this shouldn't be appended
    Enter something (type quit to quit):
    test1
    Enter something (type quit to quit):
    test2
    Enter something (type quit to quit):
    quit
    Enter something (type quit to quit): // this shouldn't print either
    [test, test1, test2]

    I don't understand why this is happening / what would be the best practice to solve I'm not appending anything until I get to my while loop.

    Thank you

  2. #2
    Super Moderator Norm's Avatar
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    Default Re: Help With coding on Arraylists and Scanner

    Take a look at this: https://stackoverflow.com/questions/...ore-the-output
    loop won't start until Scanner detects input is available, and so the program blocks waiting for input
    If you don't understand my answer, don't ignore it, ask a question.

  3. The Following User Says Thank You to Norm For This Useful Post:

    thefishvish (January 27th, 2022)

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