使用Java将数据动态插入Excel

我是Java新手，在将动态数据插入Excel文件时遇到问题。这是下面的代码。如果我删除我的excel文件并重新运行我的程序。然后，它将创建一个新文件并插入以下数据。（hello，再见，true，date）。在第一次运行期间，程序仍然可以插入以下数据，但当我执行下一次运行时，数据无法存储到下一行。以下代码用于检查文件是否存在。我希望我能找人来帮助我，因为我在这段代码中挣扎了几天

    if (file.exists()) {
                        try{
                            fout = new FileOutputStream(fileName, true);
                            fin = new FileInputStream(fileName);
                            lPOIfs = new POIFSFileSystem(fin);
                            workbook = new HSSFWorkbook(lPOIfs);
                            worksheet = workbook.getSheet("POI Worksheet");
                            for (int i=0; i<workbook.getNumberOfSheets(); i++) {
                                System.out.println( workbook.getSheetName(i) );                                    
                            }
                            HSSFSheet sheet = workbook.getSheetAt(0);
                            last = sheet.getLastRowNum();
                        }catch (IOException e) {  
                            e.printStackTrace();  
                        }catch (NullPointerException e){
                            e.printStackTrace(); 
                        }
                    } else {
                        //create new file
                        try{
                        fout = new FileOutputStream(file);                            
                        }catch (IOException e) {  
                            e.printStackTrace();  
                        }
                        workbook = new HSSFWorkbook();                       
                        worksheet = workbook.createSheet("POI Worksheet");  
                    }

这是写入函数的完整代码：

    public void writeExcel(){
    String fileName = "C:\\Users\\blslyeoh\\Documents\\NetBeansProjects\\JavaApplication1\\poi-test.xls";       
    try {
                    int last=0;
                    File file = new File(fileName);
                    FileInputStream fin = null;  
                    HSSFWorkbook workbook = null;  
                    HSSFSheet worksheet = null;  
                    FileOutputStream fout = null;
                    POIFSFileSystem lPOIfs = null;
                    if (file.exists()) {
                        try{
                            fout = new FileOutputStream(fileName, true);
                            fin = new FileInputStream(fileName);
                            lPOIfs = new POIFSFileSystem(fin);
                            workbook = new HSSFWorkbook(lPOIfs);
                            worksheet = workbook.getSheet("POI Worksheet");
                            for (int i=0; i<workbook.getNumberOfSheets(); i++) {
                                System.out.println( workbook.getSheetName(i) );                                    
                            }
                            HSSFSheet sheet = workbook.getSheetAt(0);
                            last = sheet.getLastRowNum();
                        }catch (IOException e) {  
                            e.printStackTrace();  
                        }catch (NullPointerException e){
                            e.printStackTrace(); 
                        }
                    } else {
                        //create new file
                        try{
                        fout = new FileOutputStream(file);                            
                        }catch (IOException e) {  
                            e.printStackTrace();  
                        }
                        workbook = new HSSFWorkbook();                       
                        worksheet = workbook.createSheet("POI Worksheet");  
                    }
        // index from 0,0... cell A1 is cell(0,0)
                    if(last != 0){
                        last = worksheet.getLastRowNum()+1;
                    }else{
                        last = worksheet.getLastRowNum();
                    }
                    HSSFRow row = worksheet.createRow(last);                        
        HSSFCell cellA1 = row.createCell((short)0);
        cellA1.setCellValue("hello");   
        HSSFCellStyle cellStyle = workbook.createCellStyle();
        //cellStyle.setFillForegroundColor(HSSFColor.GOLD.index);
        //cellStyle.setFillPattern(HSSFCellStyle.SOLID_FOREGROUND);
        //cellA1.setCellStyle(cellStyle);
        HSSFCell cellB1 = row.createCell((short) 1);
        cellB1.setCellValue("goodbye");
        //cellStyle = workbook.createCellStyle();
        //cellStyle.setFillForegroundColor(HSSFColor.LIGHT_CORNFLOWER_BLUE.index);
        //cellStyle.setFillPattern(HSSFCellStyle.SOLID_FOREGROUND);
        //cellB1.setCellStyle(cellStyle);
        HSSFCell cellC1 = row.createCell((short) 2);
        cellC1.setCellValue(true);

        HSSFCell cellD1 = row.createCell((short) 3);
        cellD1.setCellValue(new Date());
        cellStyle = workbook.createCellStyle();
        cellStyle.setDataFormat(HSSFDataFormat
                .getBuiltinFormat("m/d/yy h:mm"));
        cellD1.setCellStyle(cellStyle);
        workbook.write(fout);
        fout.flush();

        fout.close();
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }

public void writeExcel（）{
String fileName=“C:\\Users\\blslyeoh\\Documents\\NetBeansProjects\\JavaApplication1\\poi test.xls”；
试一试{
int last=0；
文件=新文件（文件名）；
FileInputStream fin=null；
HSSF工作簿=空；
HSSF工作表=空；
FileOutputStream fout=null；
POIFSFS文件系统lPOIfs=null；
if（file.exists（））{
试一试{
fout=新文件输出流（文件名，true）；
fin=新文件输入流（文件名）；
lPOIfs=新的POIFSFS文件系统（fin）；
工作簿=新的HSSF工作手册（lPOIfs）；
工作表=工作簿.getSheet（“POI工作表”）；
对于（int i=0；i
首先阅读excel文件
如果您通过

工作表=工作簿.getSheet（“POI工作表”）；

然后关闭文件输入流
如果无法获取工作表，请通过

工作簿=新的HSSFWorkbook（）；

工作表=工作簿.createSheet（“POI工作表”）；

您已获得现有或新的wooksheet。

追加行并将其写入文件，然后通过

fout=新文件输出流（文件）；

工作簿。书写（fout）；

fout.close（）；
我希望这能帮助你。祝你愉快：-）
你有没有收到任何stacktrace？有没有抛出错误？发布这些错误会很有帮助。我知道了，谢谢你对这个URL的帮助。希望这能帮助你。顺便说一下，fout=new FileOutputStream（fileName，true）；应该改为fout=new FileOutputStream（fileName）；顺便说一句，谢谢@jcd的关注。你能把你的代码编辑成工作代码吗？我需要这个代码。第四条建议有帮助~非常感谢：D
    public void writeExcel(){
    String fileName = "C:\\Users\\blslyeoh\\Documents\\NetBeansProjects\\JavaApplication1\\poi-test.xls";       
    try {
                    int last=0;
                    File file = new File(fileName);
                    FileInputStream fin = null;  
                    HSSFWorkbook workbook = null;  
                    HSSFSheet worksheet = null;  
                    FileOutputStream fout = null;
                    POIFSFileSystem lPOIfs = null;
                    if (file.exists()) {
                        try{
                            fout = new FileOutputStream(fileName, true);
                            fin = new FileInputStream(fileName);
                            lPOIfs = new POIFSFileSystem(fin);
                            workbook = new HSSFWorkbook(lPOIfs);
                            worksheet = workbook.getSheet("POI Worksheet");
                            for (int i=0; i<workbook.getNumberOfSheets(); i++) {
                                System.out.println( workbook.getSheetName(i) );                                    
                            }
                            HSSFSheet sheet = workbook.getSheetAt(0);
                            last = sheet.getLastRowNum();
                        }catch (IOException e) {  
                            e.printStackTrace();  
                        }catch (NullPointerException e){
                            e.printStackTrace(); 
                        }
                    } else {
                        //create new file
                        try{
                        fout = new FileOutputStream(file);                            
                        }catch (IOException e) {  
                            e.printStackTrace();  
                        }
                        workbook = new HSSFWorkbook();                       
                        worksheet = workbook.createSheet("POI Worksheet");  
                    }
        // index from 0,0... cell A1 is cell(0,0)
                    if(last != 0){
                        last = worksheet.getLastRowNum()+1;
                    }else{
                        last = worksheet.getLastRowNum();
                    }
                    HSSFRow row = worksheet.createRow(last);                        
        HSSFCell cellA1 = row.createCell((short)0);
        cellA1.setCellValue("hello");   
        HSSFCellStyle cellStyle = workbook.createCellStyle();
        //cellStyle.setFillForegroundColor(HSSFColor.GOLD.index);
        //cellStyle.setFillPattern(HSSFCellStyle.SOLID_FOREGROUND);
        //cellA1.setCellStyle(cellStyle);
        HSSFCell cellB1 = row.createCell((short) 1);
        cellB1.setCellValue("goodbye");
        //cellStyle = workbook.createCellStyle();
        //cellStyle.setFillForegroundColor(HSSFColor.LIGHT_CORNFLOWER_BLUE.index);
        //cellStyle.setFillPattern(HSSFCellStyle.SOLID_FOREGROUND);
        //cellB1.setCellStyle(cellStyle);
        HSSFCell cellC1 = row.createCell((short) 2);
        cellC1.setCellValue(true);

        HSSFCell cellD1 = row.createCell((short) 3);
        cellD1.setCellValue(new Date());
        cellStyle = workbook.createCellStyle();
        cellStyle.setDataFormat(HSSFDataFormat
                .getBuiltinFormat("m/d/yy h:mm"));
        cellD1.setCellStyle(cellStyle);
        workbook.write(fout);
        fout.flush();

        fout.close();
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }