java.lang.IllegalStateException: Scanner closed

Question

I got the following code, but after the first loop, my debugger is giving following errors,it s strange, i did it all the time like that, but it doesnt work anymore, this is pretty strange?! I checked it step-by-step, it is just stoppen after the switch order?

Exception in thread "main" java.lang.IllegalStateException: Scanner closed
        at java.util.Scanner.ensureOpen(Unknown Source)
        at java.util.Scanner.findWithinHorizon(Unknown Source)
        at java.util.Scanner.nextLine(Unknown Source)
        at Level.schleife(Level.java:35)
        at Crawler.main(Crawler.java:23)

---

public boolean schleife() {
    System.out.println("Das Spiel beginnt, bewege Dich mit der WASD Steuerung!");
    Scanner eingabeMove = new Scanner(System.in);

    tmpi = positioni;
    tmpj = positionj;
    while (true) {
        String bewegung = eingabeMove.nextLine();
        switch (bewegung) {
            case "w": {                                        // vorwärts
                tmpi += 1;
                if (actionResult()) {
                    positioni = tmpi;
                    break;
                } else {
                    return false;
                }
            }
            case "a": {                                    // links
                tmpj -= 1;
                if (actionResult()) {
                    positionj = tmpj;
                    break;
                } else {
                    return false;
                }
            }
            case "s": {                                    // rückwärts
                tmpi -= 1;
                if (actionResult()) {
                    positioni = tmpi;
                    break;
                } else {
                    return false;
                }
            }
            case "d": {                                    // rechts
                tmpj += 1;
                if (actionResult()) {
                    positionj = tmpj;
                    break;
                } else {
                    return false;
                }
            }
            default: {                                    // falsche Eingabe
                System.out.println("Falsche Eingabe!");
                continue;
            }
        }
        eingabeMove.close();
    }
}

Answer 1

Don't call eingabeMove.close(); at the end of that while loop. You're causing the Scanner to become inoperable at the end of the first loop.

Since the loop always terminates with a return, it doesn't make sense to close the Scanner in this schleife() method.

You actually don't need to close the Scanner though, because it wraps System.in which never closes anyhow. Given this fact, you can simply let eingabeMove go out of scope when the schleife() returns.

If you really want to close the Scanner, you should pass eingabeMove as a parameter to the method, and close it from the calling method.

public boolean schleife(Scanner eingabeMove) {
   // use the scanner
}

Calling code:

Scanner eingabeMove = new Scanner(System.in);
schleife(eingabeMove);
eingabeMove.close();