Question

我遇到了一个问题，即Scanner在无限期循环期间没有阻止用户输入。我尝试过使用hasNextLine()但是没有用。它只是无限地运行循环调用displayMenu()。

     do {

        displayMenu();

        int response;
        while (iStream.hasNextLine()) {
            response = Integer.parseInt(iStream.nextLine());

            switch (response) {
                case 1:
                    decodeMessage(getPhrase());
                    break;
                case 2:
                    encodeMessage(getPhrase());
                    break;
                case 3:
                    displayAlphabet();
                    break;
                case 4:
                    done = true;
                    System.out.println("Goodbye.");
                    break;
                default:
                    done = false;
            }
        }

    }
    while (!done);

我也尝试过不使用hasNextLine()，但我最终得到NoSuchElementException，因为它第一次运行完美，但在第二次迭代时，它不会阻止用户输入。< / p>

    do {

        displayMenu();

        int response = Integer.parseInt(iStream.nextLine());

            switch (response) {
                case 1:
                    decodeMessage(getPhrase());
                    break;
                case 2:
                    encodeMessage(getPhrase());
                    break;
                case 3:
                    displayAlphabet();
                    break;
                case 4:
                    done = true;
                    System.out.println("Goodbye.");
                    break;
                default:
                    done = false;

        }

    }
    while (!done);

有什么想法吗？

Answer 1

以下对我来说很好：

private static void displayMenu ()
{
    System.out.println ("Menu:");
    System.out.println ("\t1: Decode message");
    System.out.println ("\t2: Encode message");
    System.out.println ("\t3: Display alphabet");
    System.out.println ("\t4: Exit");
}

public static void main (String [] args)
{
    Scanner scanner = new Scanner (System.in);

    boolean done = false;
    while (!done)
    {
        displayMenu();

        switch (Integer.parseInt (scanner.nextLine ()))
        {
            case 1:
                System.out.println ("Decoding...");
                break;
            case 2:
                System.out.println ("Encoding...");
                break;
            case 3:
                System.out.println ("Displaying alphabet...");
                break;
            case 4:
                System.out.println("Exitting...");
                done = true;
                break;
            default:
                done = false;
        }
    }
}

循环期间Java Scanner不会阻塞

1 个答案: