添加新行后,Excel文件不会更改

我开始做一个新的过程,将excel文件中的行添加到另一个excel文件,换句话说:将行追加到现有的Excel工作表.

为此,我正在测试以下代码,基于我在Internet上找到的代码:

私人全球声明:

private HSSFRow row;
private HSSFCell cell;
private FileInputStream inFile;
private POIFSFileSystem poiFile;
private HSSFSheet excelSheet = null;
private HSSFWorkbook excelBook = null;
private FileOutputStream outFile = null;
private static String outputFileName;

我用main方法开始一切:

public static void main(String args[]){
    outputFileName = "C:\\test1.xls";
    List newContent = new ArrayList<>();
    newContent.add("Test Val1");
    newContent.add("Test Val2");
    newContent.add("Test Val3");
    testingClass test = new testingClass();
    test.overwriteExcel(outputFileName,newContent);
}

有了这个我创建了文件,并且我假装更新它:

public void overwriteExcel(String outputFileName, List newContent){
    try{
    if(new File(outputFileName).exists()){  //--If the file exists/is already created
            outFile = new FileOutputStream(new File(outputFileName),true);  /*With the "true" parameter, the change must been applied but, nothing happens...*/
            inFile = new FileInputStream(new File(outputFileName));
            poiFile = new POIFSFileSystem(inFile);
            excelBook = new HSSFWorkbook(poiFile);
            excelSheet = excelBook.getSheetAt(0);
        }else{ //--Create the file
            outFile = new FileOutputStream(new File(outputFileName));
            excelBook = new HSSFWorkbook();
            excelSheet = excelBook.createSheet("Sheet1");
        }
        int i = 0;
        for(Iterator iter = newContent.iterator(); iter.hasNext();){
            Object val = iter.next();
            if(val!=null){
                row = excelSheet.createRow(excelSheet.getLastRowNum()+1);
                cell = row.createCell(0);  //--Temporaly, I change this val manually
                cell.setCelval(newContent.get(i++));
            }
        }
        excelBook.write(outFile);
        outFile.flush();
        outFile.close();
    }catch(Exception ex){
        JOptionPane.showMessageDialog(null,"Error: "+ex.getMessage(),"Warning!",JOptionPane.ERROR_MESSAGE);
    }
}

当课程结束他的过程时,我看到了文件并且我可以感知到文件大小的变化,但是当我打开它时,一切都是一样的,在我关闭文件之后,这将返回到他之前的大小......

试图理解发生了什么,我在row.createCell(0)中将"0"更改为"1",我删除了文件并重复了一下,一切正常,但是当我再次将值更改为"0"后,更改尚未应用...我不知道是否有一些文件权限...

我认为代码有问题,这不是我第一次使用excel文件,但这是我第一次尝试修改它.

提前谢谢!