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()编写一个客户。然后我从List customerList写下所有记录并将它们保存到文件中。这很有效。

然后我想读取保存的文件，所以我使用readCustomer()读了一行。此方法返回一个Customer，然后我想使用Clients返回包含所有readData()的列表并读取它，行list.add中有nullPointerException（readCustomer（bufferedReader））; < / p>

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

您接近解决方案;）

方法：

readData(BufferedReader bufferedReader)

只需更改此行

即可

for(Customers l : list) {

到这一个：

while (bufferedReader.ready()) {

从文件中读取对象并将其保存到ArrayList中

1 个答案: