从包含多个对象的文本文件创建对象 [英] Creating an object from a text file with multiple objects

问题描述

我需要从txt文件中读取有关汽车的信息，然后将其保存到 ArrayList 。文件中的第一行告诉您文件中有多少辆汽车。

I need to read information about cars from a txt file and then saves it to an ArrayList. The first line in the file tells you how many cars are within the file.

txt文件如下所示：

The txt file looks like this:

3
2011
Toyota 
Corolla
2009
Honda
Civic 
2012
Honda
Accord

等等..

我知道如何从a创建一个对象用户输入，但我正在尝试编辑它，所以从文件中读取它。

I know how to create an object from a users input, but I am trying to edit it so reads it from a file.

推荐答案

通常我建议使用 FileReader ，但你说的是您正在重构从用户读取此信息的代码。我想，你正在用扫描仪读取输入，所以最简单的方法就是更换

Usually I would suggest using a FileReader, but you said that you are refactoring code which reads this information from the user. I guess, you are reading the input with a Scanner, so the easiest way to change this is by replacing

Scanner sc = new Scanner(System.in);

这个：

Scanner sc = new Scanner(new File("someFile.txt"));

然后您可以使用扫描仪 ：

String fileName = "cars.txt";
List<Car> cars = new ArrayList<>();
try (Scanner sc = new Scanner(new File("someFile.txt"))){
    int count = sc.nextInt();
    for (int i = 0; i < count; i++) {
        int year = sc.nextInt();
        String brand = sc.next();
        String type = sc.next();
        cars.add(new Car(year, brand, type));
    }
} catch (IOException e) {
    System.err.println("error reading cars from file "+fileName);
    e.printStackTrace();
}

还可以使用 sc.hasNext（） Scanner 中读取之前，c $ c>和 sc.hasNextInt（），因为您的代码可能会抛出异常如果文件没有有效的内容..

Also use sc.hasNext() and sc.hasNextInt() before you read from the Scanner, since your code might otherwise throw exceptions if the file doesn't have valid content..

您可以在另一个（不同的）中看到 Car 类回答我发布了

You can see the Car class in another (distinct) answer I posted

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