无法写入Excel文件（Apache POI） public静态字符串已存在（ArrayList reg\u id、ArrayList doc\u id、ArrayList status）引发rowseceededexception、WriteException、IOException{ 可写工作簿myFirstWbook=null； FileOutputStream out=新的FileOutputStream（新文件（“C://Users//Desktop//OP_demo.xlsx”）； XSSFWorkbook工作簿=新XSSFWorkbook（）； XSSFSheet sheet=workbook.createSheet（“Java书籍”）； int rowCount=0； int columnCount=0； 对于（int i=0；i

，您需要将工作簿移动到循环之外。 workbook.write（out）；将工作簿的内容写入文件流，处理完所有记录后需要写入文件，否则每次执行此操作时文件内容都会被重写

public static String already_exists(ArrayList<String> reg_id, ArrayList<String> doc_id, ArrayList<String> status) throws RowsExceededException, WriteException, IOException{
         WritableWorkbook myFirstWbook = null;
         FileOutputStream out = new FileOutputStream(new File("C://Users//Desktop//OP_demo.xlsx"));
                XSSFWorkbook workbook = new XSSFWorkbook();
                 XSSFSheet sheet = workbook.createSheet("Java Books");

                 int rowCount = 0;
                 int columnCount = 0;
                 for(int i=0;i<reg_id.size();i++)
                    {
                      Object[][] bookData={{reg_id.get(i),doc_id.get(i),status.get(i)}};
                      Row row = sheet.createRow(rowCount++); 
                      //System.out.println(reg_id.get(i)+doc_id.get(i)+status.get(i));
                      for (Object[] aBook : bookData) 
                        {

                         for (Object field : aBook) 
                            {
                             org.apache.poi.ss.usermodel.Cell cell = row.createCell(columnCount++);

                                {
                                 cell.setCellValue(field.toString());
                                }

                            }
                         workbook.write(out);


                      }


                 }

                 out.close();  

        return "";
    }

public静态字符串已存在（ArrayList reg\u id、ArrayList doc\u id、ArrayList status）引发rowseceededexception、WriteException、IOException{
可写工作簿myFirstWbook=null；
FileOutputStream out=新的FileOutputStream（新文件（“C://Users//Desktop//OP_demo.xlsx”）；
XSSFWorkbook工作簿=新XSSFWorkbook（）；
XSSFSheet sheet=workbook.createSheet（“Java书籍”）；
int rowCount=0；
int columnCount=0；
对于（int i=0；我在调用.close（）之前，尝试将“workbook.write（out）；”从循环中移出；嗨，Ankur，它成功了！我正在尝试了解它有什么不同，因为我是新手。你能解释一下吗？
public static String already_exists(ArrayList<String> reg_id, ArrayList<String> doc_id, ArrayList<String> status) throws RowsExceededException, WriteException, IOException{
             WritableWorkbook myFirstWbook = null;
             FileOutputStream out = new FileOutputStream(new File("C://Users//Desktop//OP_demo.xlsx"));
                    XSSFWorkbook workbook = new XSSFWorkbook();
                     XSSFSheet sheet = workbook.createSheet("Java Books");

                     int rowCount = 0;
                     int columnCount = 0;
                     for(int i=0;i<reg_id.size();i++)
                        {
                          Object[][] bookData={{reg_id.get(i),doc_id.get(i),status.get(i)}};
                          Row row = sheet.createRow(rowCount++); 
                          //System.out.println(reg_id.get(i)+doc_id.get(i)+status.get(i));
                          for (Object[] aBook : bookData) 
                            {

                             for (Object field : aBook) 
                                {
                                 org.apache.poi.ss.usermodel.Cell cell = row.createCell(columnCount++);

                                    {
                                     cell.setCellValue(field.toString());
                                    }

                                }

                          }

                     }

                     workbook.write(out); // writing the workbook to file-stream outside loop
                     out.close();  

            return "";
        }