方法内带有ArrayList的NoSuchElementException[重复]

Question

null

public class Player {

    private ArrayList<String> players = new ArrayList<String>();
    private int maxPlayers = 0;


    public ArrayList<String> setPlayers(ArrayList<String> strArrList) {

        Scanner sc = new Scanner(System.in);

        for (int i = 1; i <= getMaxPlayers(); i++) {

            System.out.print("Player #" + i + ": ");
            String name = sc.next();
            strArrList.add(name);
            System.out.println();

        }

        return strArrList;
    }

    public void setMaxPlayers() {

        Scanner sc = new Scanner(System.in);

        System.out.print("How many players? ");
        maxPlayers = sc.nextInt();
        System.out.println();

        sc.close();
    }

    public ArrayList<String> getPlayers() {

        return players;
    }

    public int getMaxPlayers() {

        return maxPlayers;
    }
}

public class Main {

    public static void main(String[] args) {

        Player pl = new Player();

        pl.setMaxPlayers();
        pl.setPlayers(pl.getPlayers());
    }
}

How many players? 2

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 com.arsaii.drinkgame.Player.setPlayers(Player.java:18)
    at com.arsaii.drinkgame.Main.main(Main.java:10)

Process finished with exit code 1

我知道NoSuchelementException是什么意思（有点..）但是我也尝试在main方法中的不同测试类中使用来自Player类的相同for循环，它工作了…这是否意味着我得到了一个NoSuchelementException，因为它在一个方法中…有人能解释一下吗？

Answer 1

问题是在setmaxplayers()方法中调用sc.close()时。这也将关闭基础的系统。在输入流中。

由于system.in已关闭且无法重新打开，在setplayers()中创建另一个system.in包装system.in的扫描程序将失败。

因此，最简单的解决方案，正如这里所建议的，就是如果scanner实例包装system.in时，不关闭它。只需使用一个共享的scanner实例，并且不关闭它（根本不关闭，或者至少如果您知道以后需要它的话）。