空指针异常apache poi [英] null pointer exception apache poi
问题描述
我们一直在使用 apache poi ing 我们的 java 程序读取 xls 和 xlsx 文件，问题是我们得到空指针异常有两个原因..第一个是我们已经解决的空白单元格，另一个是我们已经解决的空白单元格是当我们选择没有任何记录的某个列时..
hi we've been reading xls and xlsx file using apache poi ing our java program, the problem is we are getting null pointer exception with two reasons.. the first 1 is the blank cell which we already solved and the other one is when we are choosing a certain column that doesn't have any record..
我们的程序会询问excel文件的路径，然后是文件的具体表号和要读取的表的具体列号..这里是读取xls文件的代码
our program ask for the path of the excel file then the specific sheet number of the file and the specific column number of the sheet you want to read.. here is the code for reading xls file
public void readXLSFile()throws IOException{
InputStream ExcelFileToRead = new FileInputStream(path);
HSSFWorkbook wb = new HSSFWorkbook(ExcelFileToRead);
HSSFSheet sheet=wb.getSheetAt(sheetname);
HSSFRow row;
HSSFCell cell;
Iterator rows = sheet.rowIterator();
list1.clear();
while (rows.hasNext())
{
headers.clear();
row=(HSSFRow) rows.next();
// Iterator cells = row.cellIterator();
headers.add("contents");
cnt = cnt+1;
cell = row.getCell(cols);
if (cell.getCellType() == HSSFCell.CELL_TYPE_STRING)
{
//System.out.println(cell.getStringCellValue()+"(string)");
list.add(cell.getStringCellValue());
d.add(cell.getStringCellValue());
list1.add(new KeyValuePair(cell.getStringCellValue(),""));
}
else if(cell.getCellType() == HSSFCell.CELL_TYPE_NUMERIC)
{
//System.out.println(cell.getNumericCellValue()+"(numeric)");
double num = cell.getNumericCellValue();
String num2 = String.valueOf(num);
list.add(num2);
d.add(num2);
list1.add(new KeyValuePair(num2,""));
}
else if(cell.getCellType() == HSSFCell.CELL_TYPE_BOOLEAN)
{
//System.out.println(cell.getBooleanCellValue()+"(boolean)");
String bool = String.valueOf(cell.getBooleanCellValue());
list.add(bool);
d.add(bool);
list1.add(new KeyValuePair(bool,""));
}
else
{
//U Can Handel Boolean, Formula, Errors
}
//System.out.println();
}
arrey = list.toArray(new String[list.size()]);
data.add(d);
// System.out.println(data);
model = new DefaultTableModel();
table_1.setModel(model);
table_1.setModel(model);
model.setColumnIdentifiers(new String[] {"row","contents"});
for (KeyValuePair p : list1){
int nor=table_1.getRowCount();
int n2 = nor +1;
n1 = Integer.toString(n2);
// model.addColumn(new String [] {n1});
model.addRow(new String[] {n1,p.key, p.value});
}
// model.addColumn(new String[] {n1});
}
变量 sheetname 用于 Excel 文件的工作表编号
the variable sheetname is for the excel file's sheet number
HSSFSheet sheet=wb.getSheetAt(sheetname);
变量 cols 用于您要读取的特定列
and the variable cols is for the specific column you want to read
cell = row.getCell(cols);
我们可以读取每张工作表的第一列以及第二张工作表的第二列，但是当我编辑我的测试文件时，程序现在只能读取每张工作表的第一列..错误是空指针异常..希望你能帮忙提前致谢
we can read the first column of every sheet and also the second column of the second sheet but when i edited my test file the program now can only read the first column of every sheet.. the error is null pointer exception..wish you could help thanks in advance
推荐答案
问题是你从不测试单元格是否为空！
The issue is that you never test if the cell is null!
if (cell == null)
{
System.out.println("Cell is Empty in Column:" + cols);
} else if (cell.getCellType() == HSSFCell.CELL_TYPE_STRING)
{
//code
}
一般来说，处理 Cell.getCellType() 函数时应该小心，因为空单元格可能是 null 或 CELL_TYPE_BLANK.
As a general matter, you should be careful while handling Cell.getCellType() function, since an empty cell could be either null or be a CELL_TYPE_BLANK.
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