Apachi POI - 单元格 setCellValue 抛出 NullPointerException

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问题描述

当我尝试更新现有的 excel 文件时遇到以下错误:

When I am trying to update existing excel file I am encountering following error:

Exception in thread "main" java.lang.NullPointerException
    at xltest.main(xltest.java:28)

我的代码:

FileInputStream file = new FileInputStream(new File("C:\\Users\\onu\\test.xlsx"));

XSSFWorkbook workbook = new XSSFWorkbook(file);
XSSFSheet sheet = workbook.getSheetAt(0);

//Update the value of cell
Cell cell = sheet.getRow(0).getCell(3); // cell D1
cell.setCellValue("onu"); // line 28 which throws NPE

file.close();

FileOutputStream outFile =new FileOutputStream(new File("C:\\Users\\onu\\test.xlsx"));
workbook.write(outFile);
outFile.close();

推荐答案

单元格还不存在，所以 getCell 返回 null.

The cell does not exist yet, so getCell returns null.

如果它不存在，您必须检测到并创建单元格，使用 createCell 方法:

You must detect this and create the cell if it doesn't exist, with the createCell method:

if (cell == null)
{
    cell = sheet.getRow(0).createCell(3);
}
// Then set the value.
cell.setCellValue("onu");

或者，有 getCell 的重载，您可以在其中指定 MissingCellPolicy 以便空白 Cell如果它不存在，则会自动创建:

Alternatively, there is an overload of getCell where you can specify a MissingCellPolicy so that a blank Cell is automatically created if it didn't already exist:

cell = sheet.getRow(0).getCell(3, Row.MissingCellPolicy.CREATE_NULL_AS_BLANK);

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