从文件中读取对象并将其保存到 ArrayList

Question

我在从文件中读取特定对象并将其保存到 ArrayList 时遇到问题。

首先，我使用 writeCustomer() 写了一个客户。然后我写下 List customerList 中的所有记录并将它们保存到文件中。这很好用。

然后我想读取保存的文件，所以我使用 readCustomer() 读取了一行。这个方法 returns 一个 Customer 然后我想 return 一个包含所有 Clients 的列表使用 readData() 并阅读它，我在 [= 行中有 nullPointerException 27=](readCustomer(bufferedReader));

我的 Class Customer 有一个构造函数，并且有一个覆盖方法 toString()。

public class SaveCustomers {

public static void main(String[] args) throws IOException {

    List<Customers> customersList = new ArrayList<>();
    customersList.add(new Customers("ABC", 10));
    customersList.add(new Customers("SGS", 20));
    customersList.add(new Customers("FSD", 30));

    try (PrintWriter out = new PrintWriter("customer.txt", "UTF-8"))
    {         writeData(customersList, out);      }


    BufferedReader bufferedReader = new BufferedReader(new FileReader("customer.txt"));
    List<Customers> newList =  readData(bufferedReader);


    for(Customers c: newList){
        System.out.println(c);
    }
}

private static void writeCustomer(PrintWriter out, Customers customers){
    out.println(customers.getName()+"|"+customers.getTarrif());
}

private static void writeData(List<Customers> customersList, PrintWriter out){
    for(Customers c:customersList){
        writeCustomer(out, c);
    }
}

public static Customers readCustomer(BufferedReader bufferedReader) throws IOException {
    String line = bufferedReader.readLine();
    String [] tokens = line.split("\|");
    String name = tokens[0];
    int time = Integer.valueOf(tokens[1]);
    return new Customers(name, time);
}

public static List<Customers> readData(BufferedReader bufferedReader) throws IOException {

    List<Customers> list = new ArrayList<>();
        while (bufferedReader.readLine() != null) {
            list.add(readCustomer(bufferedReader));
        }
    return list;
}}

Answer 1

您已接近解决方案 ;)

在方法中：

readData(BufferedReader bufferedReader)

只需更改此行

for(Customers l : list) {

给这个：

while (bufferedReader.ready()) {

从文件中读取对象并将其保存到 ArrayList

Reading object from a file and saving it into ArrayList

java

arraylist

bufferedreader