java如何读写csv

读取CSV文件

使用BufferedReader逐行读取CSV文件，配合String.split()分割逗号分隔的字段。注意处理字段内包含逗号或引号的情况。

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;

public class CSVReader {
    public static void main(String[] args) {
        String csvFile = "data.csv";
        String line;
        String csvSplitBy = ",";

        try (BufferedReader br = new BufferedReader(new FileReader(csvFile))) {
            while ((line = br.readLine()) != null) {
                String[] data = line.split(csvSplitBy);
                System.out.println("Column 1: " + data[0] + ", Column 2: " + data[1]);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

对于复杂CSV格式，建议使用第三方库如OpenCSV：

import com.opencsv.CSVReader;
import java.io.FileReader;

CSVReader reader = new CSVReader(new FileReader("data.csv"));
String[] nextLine;
while ((nextLine = reader.readNext()) != null) {
    System.out.println(nextLine[0] + " | " + nextLine[1]);
}

写入CSV文件

使用FileWriter配合StringBuilder构建CSV格式内容：

import java.io.FileWriter;
import java.io.IOException;

public class CSVWriter {
    public static void main(String[] args) {
        String csvFile = "output.csv";
        try (FileWriter writer = new FileWriter(csvFile)) {
            writer.append("Name,Age\n");
            writer.append("John,30\n");
            writer.append("Jane,25\n");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

使用OpenCSV库更安全地处理特殊字符：

import com.opencsv.CSVWriter;
import java.io.FileWriter;

CSVWriter csvWriter = new CSVWriter(new FileWriter("output.csv"));
String[] header = {"Name", "Age"};
csvWriter.writeNext(header);
csvWriter.writeNext(new String[]{"John", "30"});
csvWriter.close();

处理特殊字符

当字段包含逗号或换行符时，字段应该用双引号包裹：

// 手动处理
String escapedValue = "\"" + value.replace("\"", "\"\"") + "\"";

// 使用OpenCSV自动处理
csvWriter.writeNext(new String[]{"包含,逗号的值", "正常值"});

性能优化

对于大数据量，考虑使用缓冲流：

BufferedWriter bw = new BufferedWriter(new FileWriter("large.csv"));
bw.write("header1,header2\n");
bw.flush();

第三方库推荐

1. OpenCSV：功能全面，支持注解映射

   <dependency>
       <groupId>com.opencsv</groupId>
       <artifactId>opencsv</artifactId>
       <version>5.7.1</version>
   </dependency>

2. Apache Commons CSV：轻量级解决方案

   

   <dependency>
       <groupId>org.apache.commons</groupId>
       <artifactId>commons-csv</artifactId>
       <version>1.9.0</version>
   </dependency>