Question

我正在尝试使用Scanner在程序中第二次从控制台获取输入，但在另一种方法中调用第二个Scanner时，它会出现NoSuchElement异常。

如果我从运行startMenu()中移除fileReader()它可以正常工作，但是在运行它之后由于某种原因会抛出异常。

    public class Garden {
    public static final Garden GARDEN = new Garden();
    //variable declartaions removed
    public static void main(String[] args) {
        if (null != args && 0 < args.length) {
            GARDEN.fileName = args[0].trim();
        }
        if (GARDEN.fileName != null) {
            GARDEN.fileReader(GARDEN.fileName);
        } else {
            GARDEN.fileReader();
        }

        GARDEN.startMenu();
        int mainI = 0;
        while (mainI != 1000000) {
            try {
                Thread.sleep(0);
            } catch (InterruptedException e) {
            }
            GARDEN.daysWeather();
            GARDEN.anotherDay();
            mainI++;
        }
    }


    protected void fileReader() { // asks for file name for config file
        System.out.println("Enter File Name Please");
        Scanner cmdReader = null;
        String cmdInput = null;
        try {
            cmdReader = new Scanner(System.in);
            cmdInput = cmdReader.nextLine();
        } catch (NoSuchElementException noSuchElement) {
            noSuchElement.printStackTrace();
            fileReader();  //throwing error here
        }

        //code removed
    }



    protected void startMenu() {// modified code from ATM lab (week2)
    int selected = 0;
        //code removed 
        Scanner climateScanner = new Scanner(System.in);
        System.out.println("Select a number 1-4");
        selected = climateScanner.nextInt();
        switch (selected) {
        case 1: // semiarid
            weatherType = 10; //10% chance to rain
            climateScanner.close();
            break;
        case 2: // arid
            weatherType = 20; //5% chance to rain
            climateScanner.close();
            break;
        case 3:
            weatherType = 50; //2% chance to rain
            tropicalWeather = true;
            climateScanner.close(); 
            break;
        case 4:
            weatherType = 20;//5% chance to rain 
            storming = true;
            climateScanner.close();
            break;
        default:
            System.out.println("Invalid Input try again");
            startMenu(); //using Recursion to ask for input again
            break;
        }
        //code removed
    }
}

Answer 1

 GARDEN.startMenu();// method id not a static one.

你不能以这种方式访问它。你必须初始化类或使你的方法静态。什么是GARDEN ??

好了，现在您已经编辑了代码。

再次

 GARDEN.fileReader(GARDEN.fileName); // you are parsing input argument 
                                // But method in your class is no argument method

Answer 2

问题是2个不同的Scanner（一个在startMenu（）中，一个在readFile（）中）改变了，所以在类变量中有一个Scanner scanner =新的Scanner（System.in），然后从内部调用scanner.nextLine（）方法

使用Scanner时出现NoSuchElement异常

2 个答案: