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Thread: Scanner problem

  1. #1
    Junior Member
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    Question Scanner problem

    The method below is called within a large loop in another method. The code has been boiled down to easily show the problem I'm having. I found that the method worked fine (prompts user for input, gets input, returns input) until I added a statement at the end of the method that closes the Scanner object. When the kb.close() statement is present, the method works the first time through, but subsequent calls to this method only display the prompt and the Scanner object never waits for the user to input anything thereafter. Can someone explain why this occurs and how to fix it?


    public int scanIt()
    int i;
    Scanner kb = new Scanner(System.out);
    System.out.print("==> "); // prompt for input
    i = kb.nextInt();
    System.out.println("User entered " + i);

  2. #2
    Super Moderator
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    Default Re: Scanner problem

    Welcome to the forum! Please read this topic to learn how to post code in code or highlight tags and other useful info for new members.

    Please post your code correctly per the above link.

  3. #3
    Super Moderator Norm's Avatar
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    Eastern Florida
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    Default Re: Scanner problem

    Can you make a small, complete program that compiles, executes and shows the problem?
    If you don't understand my answer, don't ignore it, ask a question.

  4. #4
    Member Ada Lovelace's Avatar
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    Default Re: Scanner problem

    Scanner kb = new Scanner(System.out);
    Should that not be in?

    Two other reasons why input is being skipped is the input object 'kb' is not
    being overwritten by the next input. It is a bug I have seen when using Net beans once before.
    To get around this - rest the input to zero at the end of the input cycle.

    Another piece of advice (which I learnt from this forum and kudos and thumbs up to Greg and Norm for this)
    is that if you are only outputting to the console you do not need to "close" the Scanner after the input. It does
    generate a warning on Eclipse - but it's just a reminder that closing Scanner may cause a resource leak if used
    with files/streams etc. You can safely ignore the error when dealing with simple console applications.

    Wishes Ada xx
    If to Err is human - then programmers are most human of us all.
    "The Analytical Engine offers a new, a vast, and a powerful language . . .
    for the purposes of mankind
    Augusta Ada Byron, Lady Lovelace (1851)

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