为何读取文本文件并正常打印时仍抛出NoSuchElementException？

我能读取文本文件的所有内容并打印数据，但仍会抛出NoSuchElementException异常。尝试了在while循环中使用hasNext()的方案，但没起作用。

原实现代码 #

public void fileReader() throws IOException {
    String id;
    String brand;
    int yearOfManufacture;
    int numSeats;
    double rentalPerDay;
    double insurancePerDay;
    double serviceFee;
    double discount;
    String model;
    String type;
    String color;
    ArrayList<Vehicle> vehicleArray = new ArrayList<>();
    File file = new File("C:/Users/jockg/Downloads/Fleet (1).csv");
    Scanner scan = new Scanner(file);
    scan.useDelimiter("n/n");

    while (scan.hasNext() || scan.hasNextDouble() || scan.hasNextInt()) {

        id = scan.next();
         System.out.println(id);
        brand = scan.next();
         System.out.println(brand);
        model = scan.next();
         System.out.println(model);
        type = scan.next();
         System.out.println(type);
        yearOfManufacture = Integer.parseInt(scan.next());
         System.out.println(yearOfManufacture);
        numSeats = Integer.parseInt(scan.next());
         System.out.println(numSeats);
        color = scan.next();
         System.out.println(color);
        rentalPerDay = Double.parseDouble(scan.next());
         System.out.println(rentalPerDay);
        insurancePerDay = Double.parseDouble(scan.next());
         System.out.println(insurancePerDay);
        serviceFee = Double.parseDouble(scan.next());
         System.out.println(serviceFee);
        if (scan.next().equals("N/A")) {
            discount = 0;
        } else {
            discount = Double.parseDouble(scan.next());
        }

         System.out.println(discount);

        Car newCar = new Car(id, brand, yearOfManufacture, numSeats, rentalPerDay, insurancePerDay, serviceFee,
                discount, model, type, color);
        vehicleArray.add(newCar);
    }
}

CSV文件内容 #

C001,Toyota,Yaris,Sedan,2012,4,Blue,50,15,10,10
C002,Toyota,Corolla,Hatch,2020,4,White,45,20,10,10
C003,Toyota,Kluger,SUV,2019,7,Grey,70,20,20,10
C004,Audi,A3,Sedan,2015,5,Red,65,10,20,10
C005,Holden,Cruze,Hatch,2020,4,Green,70,10,10,10
C006,BMW,X5,SUV,2018,7,White,100,25,20,10
C007,BMW,320i,Sedan,2021,5,Grey,75,10,15,N/A
C008,Ford,Focus,Sedan,2014,5,Red,45,10,10,N/A
C009,Ford,Puma,SUV,2015,5,Black,70,20,15,20

问题分析 #

1. 分隔符设置错误：scan.useDelimiter("n/n")完全不符合CSV格式，CSV用逗号分隔字段、每行是一条完整记录，错误的分隔符会导致Scanner读取逻辑混乱。
2. 循环条件逻辑错误：scan.hasNext() || scan.hasNextDouble() || scan.hasNextInt()使用逻辑或，只要任意一个条件为真就会继续循环，即使后续已经没有可读取的元素，最终触发NoSuchElementException。
3. 重复读取元素：处理discount时，if (scan.next().equals("N/A"))调用了一次scan.next()，如果条件不成立，又会调用一次scan.next()，导致跳过一个字段，后续读取全部错位，最终无元素可读时抛出异常。

修正后的代码 #

public void fileReader() throws IOException {
    ArrayList<Vehicle> vehicleArray = new ArrayList<>();
    File file = new File("C:/Users/jockg/Downloads/Fleet (1).csv");
    Scanner scan = new Scanner(file);

    // 逐行读取每条车辆记录
    while (scan.hasNextLine()) {
        String line = scan.nextLine();
        // 按逗号分割字段，适配CSV格式
        String[] fields = line.split(",");
        
        // 从分割后的数组中提取各字段
        String id = fields[0];
        String brand = fields[1];
        String model = fields[2];
        String type = fields[3];
        int yearOfManufacture = Integer.parseInt(fields[4]);
        int numSeats = Integer.parseInt(fields[5]);
        String color = fields[6];
        double rentalPerDay = Double.parseDouble(fields[7]);
        double insurancePerDay = Double.parseDouble(fields[8]);
        double serviceFee = Double.parseDouble(fields[9]);
        // 只读取一次discount字段，避免重复操作
        double discount = fields[10].equals("N/A") ? 0 : Double.parseDouble(fields[10]);

        // 打印验证数据
        System.out.println(id);
        System.out.println(brand);
        System.out.println(model);
        System.out.println(type);
        System.out.println(yearOfManufacture);
        System.out.println(numSeats);
        System.out.println(color);
        System.out.println(rentalPerDay);
        System.out.println(insurancePerDay);
        System.out.println(serviceFee);
        System.out.println(discount);

        // 创建车辆对象并加入集合
        Car newCar = new Car(id, brand, yearOfManufacture, numSeats, rentalPerDay, insurancePerDay, serviceFee,
                discount, model, type, color);
        vehicleArray.add(newCar);
    }
    // 关闭Scanner释放资源
    scan.close();
}

关键修改说明 #

• 逐行读取+字段分割：用hasNextLine()判断是否还有记录，nextLine()获取整行后用split(",")拆分字段，彻底避免Scanner分隔符的混乱问题。
• 避免重复读取：处理discount时只读取一次字段值，解决原代码中重复调用scan.next()导致的字段跳过和错位问题。
• 资源释放：添加scan.close()关闭Scanner，避免资源泄漏。

内容的提问来源于stack exchange，提问作者happy days