poi操作Excel，根据读取数据写入

poi操作Excel表，读取Excel表是实现了，可是怎么根据读到的数据，在写入另一个Excel文件中啊！各位，帮我在测试类中写下后半部分，多谢了！！

//实体类
public class Demo {
    private String name;
    private String rd;
    private String project;
    private String workTime;

   public Demo() {
    }

    public Demo(String name, String rd, String project, String workTime) {
        this.name = name;
        this.rd = rd;
        this.project = project;
        this.workTime = workTime;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getRd() {
        return rd;
    }

    public void setRd(String rd) {
        this.rd = rd;
    }

    public String getProject() {
        return project;
    }

    public void setProject(String project) {
        this.project = project;
    }

    public String getWorkTime() {
        return workTime;
    }

    public void setWorkTime(String workTime) {
        this.workTime = workTime;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        Demo demo = (Demo) o;
        return Objects.equals(name, demo.name) &&
                Objects.equals(rd, demo.rd) &&
                Objects.equals(project, demo.project) &&
                Objects.equals(workTime, demo.workTime);
    }

    @Override
    public int hashCode() {
        return Objects.hash(name, rd, project, workTime);
    }

    @Override
    public String toString() {
        return "Demo{" +
                "name='" + name + '\'' +
                ", rd='" + rd + '\'' +
                ", project='" + project + '\'' +
                ", workTime='" + workTime + '\'' +
                '}';
    }
}


//测试类
@Test
    public void test3() throws IOException {
        List<Demo> demoList = new ArrayList<>();
        //1.获取工作薄
        XSSFWorkbook workbook = new XSSFWorkbook("D:\\工作数据统计.xlsx");
        //2.获取工作表
        XSSFSheet sheet = workbook.getSheetAt(0);
        int lastRowNum = sheet.getLastRowNum();//最后一行索引
        for (int i =0;i<=lastRowNum;i++) {
            XSSFRow row = sheet.getRow(i);
            short cellNum = row.getLastCellNum();//获取最后一行单元格的索引
            List<String> list = new ArrayList<>();
            for (int j = 0; j <= cellNum; j++) {
                XSSFCell cell = row.getCell(j, Row.MissingCellPolicy.CREATE_NULL_AS_BLANK);
                cell.setCellType(CellType.STRING);
                String value = cell.getStringCellValue();
                list.add(value);
            }
            Demo demo = new Demo(list.get(0), list.get(1), list.get(2), (list.get(3)));
            demoList.add(demo);
        }

读取的数据，用poi生成一个excel，然后遍历往里写入数据再导出就行了

//接着你的代码之后继续写
HSSFWorkbook wb = new HSSFWorkbook();
HSSFSheet sheet = wb.createSheet();
String[] header = {"name","rd","project","workTime"};
HSSFRow row = sheet.createRow(0);
HSSFCell cell = row.createCell(j);
cell.setCellValue(header[0]);
cell.setCellValue(header[1]);
cell.setCellValue(header[2]);
cell.setCellValue(header[3]);
for (int i = 0; i < demoList.size(); i++) {
  Row row = sheet.createRow(i+1);
  Cell cellName = row.createCell(0);
  cellName.setCellValue(demoList.get(i).getName());
  Cell cellRd = row.createCell(1);
  cellRd.setCellValue(demoList.get(i).getRd());
  Cell cellProject = row.createCell(2);
  cellProject.setCellValue(demoList.get(i).getProject());
  Cell cellworkTime = row.createCell(2);
  cellworkTime.setCellValue(demoList.get(i).getWorktime());
}
FileOutputStream fileOutputStream = new FileOutputStream("工作数据统计(新).xlsx");
workbook.write(fileOutputStream);
fileOutputStream.close();

public static void writer(List<Demo> data) throws Exception {
        Workbook workbook = new XSSFWorkbook();

        //2.创建一个工作表
        Sheet sheet = workbook.createSheet("统计表");

        //列：x 行：y
        //(0,0)
        //3.创建一行 0代表第一行
        Row row1 = sheet.createRow(0);
        //4.创建一个单元格
        row1.createCell(0).setCellValue("name");
        //(1,0)第一行第二列
        row1.createCell(1).setCellValue("rd");
        row1.createCell(2).setCellValue("project");
        row1.createCell(3).setCellValue("workTime");
        for (int i = 0; i < data.size(); i++) {
            Row temp = sheet.createRow(i + 1);
            temp.createCell(0).setCellValue(data.get(i).getName());
            temp.createCell(1).setCellValue(data.get(i).getRd());
            temp.createCell(2).setCellValue(data.get(i).getProject());
            temp.createCell(3).setCellValue(data.get(i).getWorkTime());
        }
        //生成一张表（IO流） 03版本使用xlsx结尾：
        FileOutputStream fileOutputStream = new FileOutputStream("统计文件07版本.xlsx");
        //写
        workbook.write(fileOutputStream);
        //关闭
        fileOutputStream.close();
        System.out.println("07版本写入完毕");
    }