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.*;

import java.util.ArrayList;

import java.util.List;

public class WriteExcel {

    /**

     * 向Excel中写入数据

     * @param args

     * @throws Exception

     */

    public static void main(String[] args) throws Exception {

        List<Student> stuList = new ArrayList<Student>();

        stuList.add(new Student(12,"lili","深圳南山"));

        stuList.add(new Student(13,"liming","深圳宝安"));

        stuList.add(new Student(14,"chengming","深圳罗湖"));

        String filePath = "E:\\ExcelData.xlsx";

        boolean flag = fileExist(filePath);

        if (flag){

            writeExcel(stuList,filePath);

        }else {

            File file = new File(filePath);

            writeExcel(stuList,filePath);

        }

    }

    //判断文件是否存在

    public static boolean fileExist(String filePath){

        boolean flag = false;

        File file = new File(filePath);

        flag = file.exists();

        return flag;

    }

    //向Excel中写数据

    public static void writeExcel(List<Student> list ,String filePath){

        XSSFWorkbook workbook = new XSSFWorkbook();

        XSSFSheet sheet = workbook.createSheet("student");

        XSSFRow firstRow = sheet.createRow(0);//第一行表头

        XSSFCell cells[] = new XSSFCell[3];

        String[] titles = new String[]{"age","name","address"};

        //循环设置表头信息

        for (int i=0;i<3;i++){

            cells[0]=firstRow.createCell(i);

            cells[0].setCellValue(titles[i]);

        }

        //遍历list,将数据写入Excel中

        for (int i=0;i<list.size();i++){

            XSSFRow row = sheet.createRow(i+1);

            Student student = list.get(i);

            XSSFCell cell = row.createCell(0); //第一列

            cell.setCellValue(student.getAge());

            cell=row.createCell(1); //第二列

            cell.setCellValue(student.getName());

            cell=row.createCell(2); //第三列

            cell.setCellValue(student.getAddress());

        }

        OutputStream out = null;

        try {

            out = new FileOutputStream(filePath);

            workbook.write(out);

            out.close();

        } catch (Exception e){

            e.printStackTrace();

        }

    }

}

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.FileInputStream;

import java.io.FileOutputStream;

import java.util.ArrayList;

import java.util.List;

public class AddExcel {

    /**

     * 向Excel中追加内容

     * @param args

     * @throws Exception

     */

    public static void main(String[] args) throws Exception{

        List<Student> stuList2 = new ArrayList<Student>();

        stuList2.add(new Student(15,"小明","深圳南山"));

        stuList2.add(new Student(16,"小王","深圳宝安"));

        stuList2.add(new Student(17,"小张","深圳罗湖"));

        FileInputStream in = new FileInputStream("E:\\ExcelData.xlsx");

        XSSFWorkbook workbook = new XSSFWorkbook(in);

        XSSFSheet sheet = workbook.getSheetAt(0);

        XSSFRow row=sheet.getRow(1);

        FileOutputStream out = new FileOutputStream("E:\\ExcelData.xlsx");

        //从第二行开始追加列

        /*row=sheet.getRow(1);

        row.createCell(3).setCellValue("AAA");

        row.createCell(4).setCellValue("BBB");*/

        //追加列数据

        for(int i=0;i<stuList2.size();i++){

            Student student = stuList2.get(i);

            row = sheet.getRow(i+1);

            row.createCell(3).setCellValue(student.getAge());

            row.createCell(4).setCellValue(student.getName());

            row.createCell(5).setCellValue(student.getAddress());

        }

        /*//追加行数据

        row=sheet.createRow((short)(sheet.getLastRowNum()+1)); //在现有行号后追加数据

        row.createCell(0).setCellValue("测试数据"); //设置第一个（从0开始）单元格的数据

        row.createCell(1).setCellValue("haha"); //设置第二个（从0开始）单元格的数据*/

        try {

            out.flush();

            workbook.write(out);

            out.close();

        }catch (Exception e){

            e.printStackTrace();

        }

    }

}