java - 从文件中读取文本行

Question

我有一个包含 5 个客户(每行 1 个)的文本文件，客户 1、客户 2、客户 3、客户 4 和客户 5。使用以下代码，它可以完美读取 5 行文本；

import java.io.*;

public class CustomerIO  {

public void method () {

        try (BufferedReader br = new BufferedReader(new FileReader(new File ("Customers.txt")))) {
            int numberOfLines = readLines();
            String [] text = new String [numberOfLines];

            for (int i = 0; i < numberOfLines; i++) {
                text[i] = br.readLine();        
            }

            for (int i = 0; i < numberOfLines; i++) {
                System.out.println(text[i]);        
            }
        } catch (Exception e) {
            e.printStackTrace();
        }


    private int readLines() {

        try (BufferedReader br = new BufferedReader(new FileReader(new File ("Customers.txt")))) {

            while ((line = br.readLine()) != null) {
                numberOfLines++;
            }

        } catch (Exception e) {
            e.printStackTrace();
        }
        return numberOfLines;
        }
          }

但是，当我更改为以下内容时，输出为:Customer 2, Customer 4, null

import java.io.*;

public class CustomerIO  {

    String line;
    int numberOfLines = 0;

    public void method () {

        try (BufferedReader br = new BufferedReader(new FileReader(new File ("Customers.txt")))) {

            while (br.readLine() != null) {
                System.out.println(br.readLine());
            }
        } catch (Exception e) {
            e.printStackTrace();
        }


    }

    private int readLines() {

        try (BufferedReader br = new BufferedReader(new FileReader(new File ("Customers.txt")))) {

            while ((line = br.readLine()) != null) {
                numberOfLines++;
            }

        } catch (Exception e) {
            e.printStackTrace();
        }
        return numberOfLines;
        }
}

main方法包含在下面的runner.class文件中

public class Runner {

    public static void main(String[] args) {

        CustomerIO cus = new CustomerIO ();
        cus.method();
    }
}

你能帮我理解为什么会发生这种情况吗？我想在正确读取时将客户读入数组列表，而不是使用字符串 []。

谢谢

Answer 1

问题是您为每个循环调用 readline 两次。

这是您的错误代码:

while (br.readLine() != null) {
    System.out.println(br.readLine());

一个可行的解决方案可能是:

String line = br.readline();
while (line != null) {
    System.out.println(line);
    line = br.readline()
}