扫描程序 - java.util.NoSuchElementException [英] Scanner - java.util.NoSuchElementException

问题描述

有人看到这个有问题吗？第一个输入工作正常，但在第一个循环后，它不会要求再次输入值。我该如何解决这个问题？

Does anyone see a problem with this? First input works fine, but after the first loop, it doesn't ask to enter a value again. How do I fix this?

    int value;
    while(true)
    {
        Scanner scan = new Scanner(System.in);
        System.out.println("Enter a value");
        try 
        {
            value = scan.nextInt();
            System.out.println("value provided is: " + value);
            scan.nextLine(); // consumes "\n" character in buffer
        }
        catch(InputMismatchException e) // outputs error message if value provided is not an integer
        {
            System.out.println("Incorrect input type. Try again.");
            continue; // restarts while loop to allow for re-entering of a valid input
        }
        scan.close();
    }

推荐答案

移动 scan.close（）; 到之外，而循环。

还有你不必在每次迭代时构造 new Scanner 。也可以将声明移到循环外部。

Also you don't have to construct a new Scanner on each iteration. Move the declaration to outside the loop as well.

当 关闭 Scanner ，这将关闭 System.in 输入流。

When close the Scanner, this closes the System.in input stream.

所以现在当你尝试再次实例化时，它找不到任何打开的流，你就会得到那个例外。

So now when you try to instantiate it again, it doesn't find any opened stream and you'll get that exception.

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