Updating excel file using Apache POI

Question

I am trying to update an existing excel file using Apache POI. Every time I run my code I receive an error as shown below. I have also tried FileInputStreamNewFile thing.

Exception in thread "main" java.lang.NullPointerException
    at com.gma.test.WriteExcelTest.writeXLSXFile(WriteExcelTest.java:26)
    at com.gma.test.WriteExcelTest.main(WriteExcelTest.java:44)

Please find the code below. Appreciate your help.

package com.gma.test;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;

import org.apache.poi.ss.usermodel.Cell;
import org.apache.poi.xssf.usermodel.XSSFCell;
import org.apache.poi.xssf.usermodel.XSSFRow;
import org.apache.poi.xssf.usermodel.XSSFSheet;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;

public class WriteExcelTest {

    public static void writeXLSXFile(int row, int col) throws IOException {
        try {
            FileInputStream file = new FileInputStream("C:\\Anuj\\Data\\Data.xlsx");

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

            //Update the value of cell
            cell = sheet.getRow(row).getCell(col);
            cell.setCellValue("Pass");

            file.close();

            FileOutputStream outFile =new FileOutputStream(new File("C:\\Anuj\\Data\\Data.xlsx"));
            workbook.write(outFile);
            outFile.close();

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

    public static void main(String[] args) throws IOException {
        // TODO Auto-generated method stub
        writeXLSXFile(3, 3);
    }

}

check if sheet.getRow(row) is not null then cell is not null before setting the value — GUISSOUMA Issam
– GUISSOUMA Issam, Commented Aug 28, 2015 at 14:17
If you ask for a row|cell that is not defined you get a null!! — GUISSOUMA Issam
– GUISSOUMA Issam, Commented Aug 28, 2015 at 14:29

Jelle Heuzel · Accepted Answer · 2015-08-28 15:02:00Z

18

If you replace

//Update the value of cell
cell = sheet.getRow(row).getCell(col);
cell.setCellValue("Pass");

With

//Retrieve the row and check for null
HSSFRow sheetrow = sheet.getRow(row);
if(sheetrow == null){
    sheetrow = sheet.createRow(row);
}
//Update the value of cell
cell = sheetrow.getCell(col);
if(cell == null){
    cell = sheetrow.createCell(col);
}
cell.setCellValue("Pass");

It will work!

edited Aug 28, 2015 at 15:02

answered Aug 28, 2015 at 14:26

Jelle Heuzel

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3 Comments

GUISSOUMA Issam Over a year ago

What if sheet.getRow(row) return Null?

Jelle Heuzel Over a year ago

Do a similar check on the row

GUISSOUMA Issam Over a year ago

Yes, Rows and Cells are 0-based so In the example if he don't have a value on D4 he'll get a NullPointerException.

turoni · Accepted Answer · 2016-08-06 10:58:03Z

8

Thanks Jelle Heuzel for getting a good example.
I just wanted to add the resulting working code so other can incorporate it in their code faster.

I also had to use XSSFRow instead of HSSFRow but other than that it works fine for me.

package stackoverflow.appachePOI;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;

import org.apache.poi.ss.usermodel.Cell;
import org.apache.poi.xssf.usermodel.XSSFRow;
import org.apache.poi.xssf.usermodel.XSSFSheet;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;

public class WriteExcelTest {

    public static void writeXLSXFile(int row, int col) throws IOException {
        try {
            FileInputStream file = new FileInputStream("C:\\Users\\Sam\\files\\Masterproef lca\\lca-analysebeheer\\Test-Files\\exceltemplates\\template.xlsx");

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

            //Retrieve the row and check for null
            XSSFRow sheetrow = sheet.getRow(row);
            if(sheetrow == null){
                sheetrow = sheet.createRow(row);
            }
            //Update the value of cell
            cell = sheetrow.getCell(col);
            if(cell == null){
                cell = sheetrow.createCell(col);
            }
            cell.setCellValue("Pass");

            file.close();

            FileOutputStream outFile =new FileOutputStream(new File("C:\\Users\\Sam\\files\\Masterproef lca\\lca-analysebeheer\\Test-Files\\exceltemplates\\Output.xlsx"));
            workbook.write(outFile);
            outFile.close();

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

    public static void main(String[] args) throws IOException {
        // TODO Auto-generated method stub
        writeXLSXFile(3, 3);
    }

}

edited Aug 6, 2016 at 10:58

answered Jun 22, 2016 at 14:04

turoni

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2 Comments

abhiburk Over a year ago

Gives Null Pointer Exception here XSSFSheet sheet = workbook.getSheetAt(0); any one here ?

turoni Over a year ago

First guess is something went wrong in your filestream and your workbook could not be created.

diego matos - keke · Accepted Answer · 2016-08-16 17:34:06Z

i tried with this and work for XLSX and XSSF

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;

import org.apache.poi.ss.usermodel.Cell;
import org.apache.poi.xssf.usermodel.XSSFRow;
import org.apache.poi.xssf.usermodel.XSSFSheet;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;

public class TestStackOver {

    public static void writeXLSXFile(int row, int col) throws IOException {
        try {
            FileInputStream file = new FileInputStream(Constante.ruta);
            XSSFWorkbook workbook = new XSSFWorkbook(file);
            XSSFSheet sheet = workbook.getSheetAt(0);
            Cell cell = null;
          //Retrieve the row and check for null
            XSSFRow sheetrow = sheet.getRow(row);
            if(sheetrow == null){
                sheetrow = sheet.createRow(row);
            }
            //Update the value of cell
            cell = sheetrow.getCell(col);
            if(cell == null){
                cell = sheetrow.createCell(col);
            }
            cell.setCellValue("Pass");

            file.close();


            FileOutputStream outFile =new FileOutputStream(new File(Constante.ruta_salida));
            workbook.write(outFile);
            outFile.close();

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

    public static void main(String[] args) throws IOException {
        // TODO Auto-generated method stub
        System.out.println("inicio");
        writeXLSXFile(1, 14);
        System.out.println("terminado");
    }

}

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