从每个 ArrayList 对象具有多个值的 ArrayList 写入文本文件 (java)

Question

我正在尝试将 ArrayList 保存到文本文件中。但是保存的格式是错误的。我的代码：

ArrayList<Vehicle> vehs = new ArrayList<Vehicle>();

vehs.add(new Vehicle("QJT123", "Starlet 99", 35.0, 190000));
vehs.add(new PremiumVehicle("TUX132", "BWM 05  ", 90.0, 12000, 100, 10000, 5000));

用于这 2 个的构造函数：

public PremiumVehicle(String vehicleID, String description, double dailyRate, int odometer, int allowance, int serLength, int lastOdo) //subclass

public Vehicle(String vehicleID, String description, double dailyRate, int odometer) //Superclass

这两个都存储在 Vehicle ArrayList 中。保存到文本文件的代码：

private static void saveFile(ArrayList<Vehicle> vehs){
    File fileName = new File("VehicleList.txt");        

    try {
        FileWriter fw = new FileWriter(fileName);
        Writer output = new BufferedWriter(fw);

        for (int i = 0; i < vehs.size(); i++){
            output.write(vehs.get(i).toString() + "\n");
        }

        output.close();

    } catch (Exception e) {
        JOptionPane.showMessageDialog(null, "I cannot create that file");
    }
}

我在 VehicleList.txt 中的输出：

vehicle ID = QJT123 Description = Starlet 99    Status = A  Daily Rate = 35.0 Odometer reading = 190000vehicle ID = TUX132  Description = BWM 05    Status = A  Daily Rate = 90.0   Odometer reading = 12000 Mileage allowance = 100    service length = 10000  Last Service = 5000

如何在写入新的 ArrayList 对象时添加每一行，例如：

vehicle ID = QJT123 Description = Starlet 99    Status = A  Daily Rate = 35.0 Odometer reading = 190000
vehicle ID = TUX132 Description = BWM 05    Status = A  Daily Rate = 90.0   Odometer reading = 12000 Mileage allowance = 100    service length = 10000  Last Service = 5000

我试过使用 vehs.get(i).toString() + "\n" 但它似乎不起作用。

Answer 1

BufferedWriter 有一个 newLine() 方法，如果你将 output 声明为 BufferedWriter ，你可以使用它。

private static void saveFile(ArrayList<Vehicle> vehs){
    File fileName = new File("VehicleList.txt"); 


    try {
        FileWriter fw = new FileWriter(fileName);
        BufferedWriter output = new BufferedWriter(fw);

        for (int i = 0; i < vehs.size(); i++){
            output.write(vehs.get(i).toString());
            output.newLine();
        }

        output.close();

    } catch (Exception e) {
        JOptionPane.showMessageDialog(null, "I cannot create that file");
    }
}

还有方法的 javadoc :

Writes a line separator. The line separator string is defined by the system property line.separator, and is not necessarily a single newline ('\n') character.

Answer 2

很可能，您的平台不会将 \n 视为换行符 - 这取决于 OS。

获取正确换行符的一种方法：

String lineSep = System.getProperty("line.separator");

或更简单：

String lineSep = System.lineSeparator();

而不是使用 + "\n"，而是在代码中使用 + lineSep。

从每个 ArrayList 对象具有多个值的 ArrayList 写入文本文件 (java)

Writing into text file from ArrayList that has multiple values per ArrayList object (java)

java

arraylist

text-files

bufferedreader

filewriter