how to solve NoSuchElementException Error in Scanner of Java?

Question

I am making a simple console game where player is allowed to move in x ,-x, y,-y directions according to String input collected from keyboard as a, d, w and s respectively , but scanner is throwing NoSuchElementException, I tried collecting data with nextInt() too ,but I was getting similar exception. Note: But scanner works for one time i.e. first time.

My Code

   private static void gamePlay(boolean isPlaying) {

    while (isPlaying) {

        System.out.println("Choose a, d , s or w for movement:");
        Scanner sc = new Scanner(System.in);
        String choice = sc.next();
        sc.close();
        // code for movement of player according to a or s or d or w
        switch (choice) {
            case "a":
                // Some code here
                // move -x
                break;

            case "d":
                // Some code here
                // move +x

                break;

            case "w":
                // Some code here
                // move +y

                break;

            case "s":
                // Some code here
                // move -y

                break;
            case "q":
                //quit 
                isPlaying = false;
                break;

            default:
                break;

        }

    }

}

** Output**

    Choose a, d , s or w for movement:
    a
    Choose a, d , s or w for movement:
    Exception in thread "main" java.util.NoSuchElementException
    at java.base/java.util.Scanner.throwFor(Scanner.java:937)
    at java.base/java.util.Scanner.next(Scanner.java:1478)
    at App.gamePlay(App.java:37)
    at App.main(App.java:17)

TL;DR: When you `close()` the `Scanner` it also closes the underlying stream (`System.in` in this case). Solution: Don't close a `Scanner` wrapping `System.in`, make it a class level variable and reuse it as long as you need to. — maloomeister, May 12 '22 at 10:00
just move your sc.close() out of your while loop, and eventually change the scope of your sc varibale, so it is declared out of the while loop too — Helix112, May 12 '22 at 10:06
@roshannepal_x , you can instanciate the scanner only once before the while loop in your play method — Helix112, May 12 '22 at 10:12
should i upload my corrected code in my post so as to help other? — roshannepal_x, May 12 '22 at 10:15
@roshannepal_x , yes if you want to. Maybe someone will come with a better explanation of why that solves your issue — Helix112, May 12 '22 at 10:16
yes understanding the issue is more important than solving it. — roshannepal_x, May 12 '22 at 10:19

score 0 · Accepted Answer · answered May 12 '22 at 13:00

private static void gamePlay(boolean isPlaying) {

    while (isPlaying) {

        System.out.println("Choose a, d , s or w for movement:");
        Scanner sc = new Scanner(System.in);
        String choice = sc.next();
        // code for movement of player according to a or s or d or w
        switch (choice) {
            case "a":
                // Some code here
                // move -x
                break;

            case "d":
                // Some code here
                // move +x

                break;

            case "w":
                // Some code here
                // move +y

                break;

            case "s":
                // Some code here
                // move -y

                break;
            case "q":
                //quit
                sc.close();
                isPlaying = false;
                break;

            default:
                break;
        }

    }
}

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how to solve NoSuchElementException Error in Scanner of Java?

1 Answers1