如何使用 POI 避免空单元格出现 NullPointerException？

Question

我正在尝试使用 Apache POI 从 excel.xlsx 文件中获取我的 java 程序中的一些值，但我遇到了麻烦，因为我的循环有时会遇到一个空单元格，然后我得到一个 NullPointerException。我怎样才能 "test" 在阅读单元格之前？这是我的一段代码：

FileInputStream file = new FileInputStream(new File(file));
XSSFWorkbook workbook = new XSSFWorkbook(file);
XSSFSheet sheet = workbook.getSheetAt(0);
int rows;
rows = sheet.getPhysicalNumberOfRows();
for (int i=1;i<rows;i++){
    Row row = sheet.getRow(i);
    Cell cell = row.getCell(2); // Here is the NullPointerException
    String cellString = cell.getStringCellValue();
    myArrayList.add(cellString);
}

这让我想到：

java.lang.NullPointerException
at analyse.Analyser.getExcelWords3(Analyser.java:73)
at analyse.Analyser.main(Analyser.java:21)

我想知道是否有可能在尝试读取之前检查单元格是否为空，这样我就不会得到 NPE。提前致谢！

Answer 1

将您的代码包装在 try / catch 语句中，这就是它的用途.. https://docs.oracle.com/javase/tutorial/essential/exceptions/catch.html

下面一些未经测试的代码可为您提供思路：

for (int i=1;i<rows;i++){
    try{
        Row row = sheet.getRow(i);
        Cell cell = row.getCell(2); // Here is the NullPointerException
        String cellString = cell.getStringCellValue();
        myArrayList.add(cellString);
    }catch(NullPointerException NPE)
    {
        //what to do when the exception occurs?
    }
}

Answer 2

看这个方法：

/**
 * Returns the cell at the given (0 based) index, with the specified {@link org.apache.poi.ss.usermodel.Row.MissingCellPolicy}
 *
 * @return the cell at the given (0 based) index
 * @throws IllegalArgumentException if cellnum < 0 or the specified MissingCellPolicy is invalid
 * @see Row#RETURN_NULL_AND_BLANK
 * @see Row#RETURN_BLANK_AS_NULL
 * @see Row#CREATE_NULL_AS_BLANK
 */
public XSSFCell getCell(int cellnum, MissingCellPolicy policy) {

应该对你有帮助。

Answer 3

`       FileInputStream file = new FileInputStream(new File(file));
     XSSFWorkbook workbook = new XSSFWorkbook(file);
     XSSFSheet sheet = workbook.getSheetAt(0);
     int rows;
     String cellString = null;
     rows = sheet.getPhysicalNumberOfRows();
    for (int i=1;i<rows;i++){
    Row row = sheet.getRow(i);
    if(row.getCell(2) == null)
    {
    cellString = null;
    }
    else
    {
    Cell cell = row.getCell(2); //if 3rd column of excelsheet then     getCell(2)..
    cellString = cell.getStringCellValue();
    }
    myArrayList.add(cellString);
    }
      if excel cell contain empty/blank then it will be stored as null`

Answer 4

为避免 NullPointerException 添加这个 Row.MissingCellPolicy.CREATE_NULL_AS_BLANK

Cell cell = row.getCell(j, Row.MissingCellPolicy.CREATE_NULL_AS_BLANK);

这将创建一个空白单元格而不是给你 NPE

如何使用 POI 避免空单元格出现 NullPointerException？

How to avoid NullPointerException with an empty cell using POI?

java

excel

cell

nullpointerexception

apache-poi