java生成Excel或CSV文件并写入数据

引入Maven依赖：

    <dependency>
      <groupId>org.apache.poi</groupId>
      <artifactId>poi</artifactId>
      <version>3.17</version>
    </dependency>
    <dependency>
      <groupId>org.apache.poi</groupId>
      <artifactId>poi-ooxml</artifactId>
      <version>3.17</version>
    </dependency>

Java将数据写入Excel，把这个方法封装了WriteToExcel

import org.apache.poi.xssf.usermodel.XSSFCell;
import org.apache.poi.xssf.usermodel.XSSFRow;
import org.apache.poi.xssf.usermodel.XSSFSheet;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;
 
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
 
public class WriteToExcel {
 
    private static XSSFWorkbook workbook;
    private static XSSFSheet sheet;
    private static XSSFRow row;
    private static XSSFCell cell;
    private static File file;
 
    //创建sheet页
    public static void setSheet(String sheetName) {
        workbook = new XSSFWorkbook();
        sheet = workbook.createSheet(sheetName);
    }
    //创建表头
    public static void createHead(List<String> headList) {
        //创建表头，也就是第一行
        row = sheet.createRow(0);
        for (int i = 0; i < headList.size(); i++) {
            cell = row.createCell(i);
            cell.setCellValue(headList.get(i));
        }
    }
    //创建表内容
    public static void createContent(List<List<String>> contentList) {
        //创建表内容，从第二行开始
        for (int i = 0; i < contentList.size(); i++) {
            row = sheet.createRow(i + 1);
            for (int j = 0; j < contentList.get(i).size(); j++) {
                row.createCell(j).setCellValue(contentList.get(i).get(j));
            }
        }
    }
    //写入文件
    public static void writeToFile(String filePath){
        file = new File(filePath);
        //将文件保存到指定的位置
        try {
            workbook.write(new FileOutputStream(file));
            System.out.println("写入成功");
            workbook.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    // 内容测试数据
    protected static List<List<String>> getContent() {
        List<List<String>> contentList = new ArrayList<>();
        List<String> content1 = new ArrayList<>();
        content1.add("张三");
        content1.add("18");
        List<String> content2 = new ArrayList<>();
        content2.add("李四");
        content2.add("20");
        contentList.add(content1);
        contentList.add(content2);
        return contentList;
    }
    
    public static void main(String[] args) {
        //表头测试数据
        List<String> headList = new ArrayList<>();
        headList.add("昵称");
        headList.add("年龄");
        List<List<String>> contentList = getContent();//内容测试数据
        setSheet("WorkSheet");                        //创建sheet页
        createHead(headList);                         //设置表头
        createContent(contentList);                   //设置内容
        writeToFile("D://work.xls");         //写入文件
    }
}

将excel转换为csv

import org.apache.commons.io.FilenameUtils;
import org.apache.poi.ss.usermodel.Cell;
import org.apache.poi.xssf.usermodel.XSSFCell;
import org.apache.poi.xssf.usermodel.XSSFRow;
import org.apache.poi.xssf.usermodel.XSSFSheet;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.util.Iterator;

/**
 * @Description: XlsxtoCSV
 * @author: muxianghui
 * @date: 2023年04月27日 9:56
 */
public class XlsxtoCSV {
    public static void xlsx(File inputFile, File outputFile) {
        StringBuffer data = new StringBuffer();
        try {
            FileOutputStream fos = new FileOutputStream(outputFile);
            FileInputStream fis = new FileInputStream(inputFile);
            XSSFWorkbook workbook = null;

            String ext = FilenameUtils.getExtension(inputFile.toString());

            if (ext.equalsIgnoreCase("xlsx")) {
                workbook = new XSSFWorkbook(fis);
            } else if (ext.equalsIgnoreCase("xls")) {
                workbook = new XSSFWorkbook(fis);
            }
            int numberOfSheets = workbook.getNumberOfSheets();
            XSSFRow row;
            XSSFCell cell;
            for (int i = 0; i < numberOfSheets; i++) {
                XSSFSheet sheet = workbook.getSheetAt(0);
                Iterator rowIterator = sheet.iterator();

                while (rowIterator.hasNext()) {
                    row = (XSSFRow) rowIterator.next();
                    Iterator cellIterator = row.cellIterator();
                    while (cellIterator.hasNext()) {

                        cell = (XSSFCell) cellIterator.next();

                        switch (cell.getCellType()) {
                            case Cell.CELL_TYPE_BOOLEAN:
                                data.append(cell.getBooleanCellValue() + ",");

                                break;
                            case Cell.CELL_TYPE_NUMERIC:
                                data.append(cell.getNumericCellValue() + ",");

                                break;
                            case Cell.CELL_TYPE_STRING:
                                data.append(cell.getStringCellValue() + ",");
                                break;

                            case Cell.CELL_TYPE_BLANK:
                                data.append("" + ",");
                                break;
                            default:
                                data.append(cell + ",");

                        }
                    }
                    data.append('\n'); // appending new line after each row
                }

            }
            fos.write(data.toString().getBytes());
            fos.close();
        } catch (Exception ioe) {
            ioe.printStackTrace();
        }
    }

注意事项：

如果打开文件提示“文件格式和扩展名不匹配。。。”，立刻想到这是由于生成的文件有问题。

解决一：需要修改代码重新生成；

解决二：通过文件转换方式生成；