Java中Scanner读取文本为Vehicle子类Car字段赋值失败求助

我是Java新手，开发包含三个类的项目时遇到问题：用Scanner读取文本文件给Vehicle和其子类Car的字段赋值，仅Vehicle的字段成功，Car的isConvertible始终为false、numOfDoors始终为0。

问题根源 #

1. Vehicle类readDetails方法错误处理Scanner：父类方法中调用scanner.nextLine()并新建、关闭Scanner，直接耗尽传入的Scanner资源，导致子类后续无法读取剩余字段。
2. Car类readDetails方法逻辑冗余：子类中重复写了读取整行的逻辑，但传入的Scanner是针对单行文本的，无多行可读取，且父类已关闭Scanner，子类无法继续读取。
3. Vehicle类字段冗余：Vehicle中定义了isConvertible和numOfDoors，这两个是Car专属字段，属于设计冗余。
4. Car类构造方法无效赋值：isConvertible = this.isConvertible;这类代码无意义，默认值本身就是false和0。
5. Car类printDetails依赖未实现方法：ShowVehicleModel()等方法不存在，会导致编译错误。

修改方案 #

1. 重构Vehicle类 #

• 删除冗余的isConvertible和numOfDoors字段
• 修改readDetails方法，直接使用传入的Scanner读取字段，不新建/关闭Scanner
• 添加getter方法供子类访问私有字段

2. 重构Car类 #

• 删除构造方法中的无效赋值
• 修改readDetails方法，去掉整行读取逻辑，直接调用父类方法后读取专属字段
• 修复printDetails方法，使用父类getter获取字段值

3. 调整RentShop类 #

• 保持当前单行读取逻辑，确保传入Car的Scanner是针对单行文本的

修改后的代码 #

Vehicle类 #

import java.util.NoSuchElementException;
import java.util.Scanner;

public class Vehicle {
    private String vehicleModel;
    String vehicleCode;
    private int timesRented;
    private boolean onRent;
    private int price;
    private int vehiclePlateNum;

    public Vehicle() {
    }

    public void printDetails() {
        System.out.println("Vehicle model: " + vehicleModel + "; code: " + vehicleCode
                + "; timesRented: " + timesRented + "; onRent: " + onRent + "; price: " + price
                + "; vehiclePlateNum: " + vehiclePlateNum);
    }

    public void readDetails(Scanner scanner) {
        try {
            vehicleModel = scanner.next().trim();
            vehicleCode = scanner.next().trim();
            timesRented = Integer.parseInt(scanner.next().trim());
            onRent = Boolean.parseBoolean(scanner.next().trim());
            price = Integer.parseInt(scanner.next().trim());
            vehiclePlateNum = Integer.parseInt(scanner.next().trim());
        } catch (NoSuchElementException e) {
            System.out.println("Error reading vehicle data: " + e.getMessage());
        }
    }

    // 供子类使用的getter方法
    public String getVehicleModel() {
        return vehicleModel;
    }

    public String getVehicleCode() {
        return vehicleCode;
    }

    public int getTimesRented() {
        return timesRented;
    }

    public boolean isOnRent() {
        return onRent;
    }

    public int getPrice() {
        return price;
    }

    public int getVehiclePlateNum() {
        return vehiclePlateNum;
    }
}

Car类 #

import java.util.NoSuchElementException;
import java.util.Scanner;

public class Car extends Vehicle {
    private boolean isConvertible;
    private int numOfDoors;

    public Car() {
        super();
    }

    @Override
    public void printDetails() {
        System.out.println("Vehicle model: " + getVehicleModel() + "; code: " + getVehicleCode()
                + "; timesRented: " + getTimesRented() + "; onRent: " + isOnRent() + "; price: "
                + getPrice() + "; vehiclePlateNum: " + getVehiclePlateNum() + "; isConvertible: "
                + isConvertible + "; numOfDoors: " + numOfDoors);
    }

    @Override
    public void readDetails(Scanner scanner) {
        try {
            super.readDetails(scanner);
            this.isConvertible = Boolean.parseBoolean(scanner.next().trim());
            this.numOfDoors = Integer.parseInt(scanner.next().trim());
        } catch (NoSuchElementException e) {
            System.out.println("Error reading car data: " + e.getMessage());
        }
    }
}

RentShop类 #

import java.io.File;
import java.io.FileNotFoundException;
import java.util.ArrayList;
import java.util.Scanner;
import javax.swing.JFileChooser;

public class RentShop {
    public ArrayList<Vehicle> vehicleList;

    public RentShop() {
        vehicleList = new ArrayList<Vehicle>();
    }

    public void storeVehicle(Vehicle vehicle) {
        vehicleList.add(vehicle);
    }

    public void printAllVehicles() {
        for (Vehicle vehicle : vehicleList) {
            vehicle.printDetails();
        }
    }

    public void readDetails() {
        JFileChooser fileChooser = new JFileChooser();
        fileChooser.setDialogTitle("Select Vehicle Data File");
        fileChooser.setFileSelectionMode(JFileChooser.FILES_ONLY);
        fileChooser.setAcceptAllFileFilterUsed(false);
        fileChooser.setCurrentDirectory(new File(System.getProperty("user.dir")));
        int result = fileChooser.showOpenDialog(null);
        if (result == JFileChooser.APPROVE_OPTION) {
            File selectedFile = fileChooser.getSelectedFile();
            try {
                Scanner scanner = new Scanner(selectedFile);
                while (scanner.hasNextLine()) {
                    String lineOfText = scanner.nextLine().trim();
                    System.out.println(lineOfText);

                    Scanner lineScanner = new Scanner(lineOfText);
                    lineScanner.useDelimiter(",");

                    Car car = new Car();
                    car.readDetails(lineScanner);
                    vehicleList.add(car);

                    lineScanner.close();
                }

                scanner.close();
                printAllVehicles();
            } catch (FileNotFoundException e) {
                System.out.println("File not found: " + e.getMessage());
            }
        }
    }
}

验证说明 #

修改后运行RentShop的readDetails方法，文本文件每行数据会被正确拆分：前6个字段赋值给Vehicle父类，后2个字段赋值给Car子类，printDetails可完整输出所有字段值，包括isConvertible和numOfDoors。

内容的提问来源于stack exchange，提问作者Some dude