csv工具类

package com.cwp.utils;

import cn.hutool.core.io.FileUtil;
import cn.hutool.core.util.CharsetUtil;
import org.apache.commons.lang3.StringUtils;

import java.io.*;
import java.util.ArrayList;
import java.util.List;

public class MyCsvUtil {

    /**
     * CSV文件生成方法  字符流追加：FileWriter writer = new FileWriter(file，true)
     *
     * @param headLabel 头部标签
     * @param dataList  数据列表
     * @param csvFile  文件
     * @param addFlag   是否追加
     */
    public static void  writeToCsv(String headLabel, List<String> dataList, File csvFile, boolean addFlag) {

        BufferedWriter buffWriter = null;
        try {

            //文件输出流对象，第二个参数时boolean类型,为true表示文件追加（在已有的文件中追加内容）
          /*  FileWriter writer = new FileWriter(csvFile, addFlag);*/
            buffWriter =  FileUtil.getWriter(csvFile, CharsetUtil.CHARSET_GBK,addFlag);
            //构建缓存字符输出流（不推荐使用OutputStreamWriter）
           /* buffWriter = new BufferedWriter(writer, 1024);*/
            //头部不为空则写入头部，并且换行
            if (StringUtils.isNotBlank(headLabel)) {
                buffWriter.write(headLabel);
                buffWriter.newLine();
            }
            //遍历list
            for (String rowStr : dataList) {
                //如果数据不为空，则写入文件内容,并且换行
                if (StringUtils.isNotBlank(rowStr)) {
                    buffWriter.write(rowStr);
                    buffWriter.newLine();//文件写完最后一个换行不用处理
                }
            }
            //刷新流，也就是把缓存中剩余的内容输出到文件
            buffWriter.flush();
        } catch (Exception e) {
            System.out.println("写入csv出现异常");
            e.printStackTrace();
        } finally {
            try {
                //关闭流
                if (buffWriter != null) {
                    buffWriter.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }



    /**
     * 根据文件路径读取csv文件的内容
     *
     * @param filePath
     * @return
     */
    public static List<String> readFromCsv(String filePath) {
        ArrayList<String> dataList = new ArrayList<>();
        BufferedReader buffReader = null;
        try {
            //构建文件对象
            File csvFile = new File(filePath);
            //判断文件是否存在
            if (!csvFile.exists()) {
                System.out.println("文件不存在");
                return dataList;
            }
            //构建字符输入流
            buffReader =  FileUtil.getReader(csvFile, CharsetUtil.CHARSET_GBK);
           /* FileReader fileReader = new FileReader(csvFile);*/
            //构建缓存字符输入流
           /* buffReader = new BufferedReader(fileReader);*/
            String line = "";
            //根据合适的换行符来读取一行数据,赋值给line
            while ((line = buffReader.readLine()) != null) {
                if (StringUtils.isNotBlank(line)) {
                    //数据不为空则加入列表
                    dataList.add(line);
                }
            }
        } catch (Exception e) {
            System.out.println("读取csv文件发生异常");
            e.printStackTrace();
        } finally {
            try {
                //关闭流
                if (buffReader != null) {
                    buffReader.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return dataList;
    }


    private static void appendToCsvExample() {
       String csvfile = "E:\\csv\\对账文件20211111.csv";
       File csvFile=new File(csvfile);
        List<String> dataList = new ArrayList<>();
        dataList.add("190469730006,100011,4000,4000,0,105000041112608,01,00,2021-09-12 16:52:57,8");
        dataList.add("190469730173,100011,4000,4000,0,105000041112608,01,00,2021-09-12 16:53:54,8");
        dataList.add("190469730367,100011,4000,4000,0,105000041112608,01,00,2021-09-12 16:54:50,8");
        dataList.add("190469736543,100011,4000,4000,0,105000041112608,01,00,2021-09-12 17:25:53,8");
        dataList.add("190469746558,100011,4000,4000,0,105000041112608,01,00,2021-09-12 18:14:13,8");
        MyCsvUtil.writeToCsv("", dataList, csvFile, true);
    }


    private static void writeToCsvExample() {
        String headDataStr = "交易流水,商户编号,订单金额,支付金额,优惠金额,收款账户,支付方式,支付状态,支付时间,交易类型";
         String csvfile = "E:\\csv\\对账文件20211111.csv";
        List<String> dataList = new ArrayList<>();
        File csvFile=new File(csvfile);
       /* dataList.add("190469644375,100011,4000,4000,0,105000041112608,03,00,2021-09-12 07:44:12,8");
        dataList.add("190469644954,100011,4000,4000,0,105000041112608,03,00,2021-09-12 07:50:10,8");
        dataList.add("190469645620,100011,4000,4000,0,105000041112608,03,00,2021-09-12 07:56:59,8");
        dataList.add("190469661593,100011,2000,2000,0,105000041112608,01,00,2021-09-12 09:51:24,8");
        dataList.add("190469661738,100011,2000,2000,0,105000041112608,01,00,2021-09-12 09:52:15,8");
        dataList.add("190469661853,100011,2000,2000,0,105000041112608,01,00,2021-09-12 09:52:51,8");
        dataList.add("190469661931,100011,2000,2000,0,105000041112608,01,00,2021-09-12 09:53:27,8");
        dataList.add("190469699471,100011,2000,2000,0,105000041112608,03,00,2021-09-12 13:59:02,8");
        dataList.add("190469699540,100011,2000,2000,0,105000041112608,03,00,2021-09-12 13:59:29,8");
        dataList.add("190469712840,100011,4000,4000,0,105000041112608,03,00,2021-09-12 15:20:32,8");*/
        MyCsvUtil.writeToCsv(headDataStr, dataList, csvFile, false);
    }

    private static void readFromCsvExample() {
        String csvFilePath = "E:\\csv\\对账文件20211111.csv";
        List<String> list = MyCsvUtil.readFromCsv(csvFilePath);
        for (String data : list) {
            System.out.println(data);
        }
    }


  public static void main(String[] args) {

      writeToCsvExample();
      appendToCsvExample();
      readFromCsvExample();

  }
}

参考文章：Java实现CSV文件的读写（包含追加内容）_嘉禾嘉宁papa-优快云博客目录一、简介二、maven依赖或jar三、CSV工具类四、CSV读写测试4.1、文件写入4.2、文件内容追加4.3、文件读取结语一、简介  逗号分隔值（Comma-Separated Values，CSV，有时也称为字符分隔值，因为分隔字符也可以不是逗号），其文件以纯文本形式存储表格数据（数字和文本）。纯文本意味着该文件是一个字符序列，不含必须像二进制数字那样被解读的数据，CSV文件的特点：文件由任意数目的记录组成每条记录由字段组成，字段间的分隔符是其它字符或字符串，最常见的是逗号或制表符记录间https://blog.youkuaiyun.com/Alian_1223/article/details/121243848

opencsv项目参考地址：How to read and parse CSV file in Java - Mkyong.comTalks about CSV file parsing, RFC 4180, OpenCSV and Single class implementation examples to read and parse a CSV file.https://mkyong.com/java/how-to-read-and-parse-csv-file-in-java/