We help IT Professionals succeed at work.
Get Started

Can I speed up Apache POI when working with xlsx files?

Last Modified: 2016-03-26
I have been using POI for a few years to generate excel files for users.  I've recently had to move from xls files (HSSF) to xlsx files (XSSF) due to the number of rows in a particular export.  Unfortunately, this has resulted in a massive performance loss.  

My use case usually involves a template file that I open and create sheet(s) inside.  Generally there will be some pivot charts and/or other static data in these templates which is why my test uses an empty 'template' file, if I didn't say this someone would suggest using streaming, which would be nice, but I can't lose my template sheets (or the styles on them).

So, here's a fairly simple demonstration:

//import org.apache.poi.hssf.usermodel.HSSFWorkbook;
//import org.apache.poi.xssf.usermodel.XSSFWorkbook;
import org.apache.poi.ss.usermodel.*;
import org.apache.poi.ss.util.*;

import java.io.*;
import java.util.*;

public class ExcelTest {
	static public int NUM_ROWS = 10000;
	static public int NUM_COLS = 25;
	private Workbook workbook;
	private Sheet cSheet;
	private boolean useHSSF;
	public ExcelTest(boolean useHSSF) {
		this.useHSSF = useHSSF;
	public boolean Test() {
		boolean tbr = true;
		try {
			//Open template xlsx file.  This is a single workbook with a single, empty sheet:
			this.workbook = WorkbookFactory.create(new FileInputStream((this.useHSSF ? "data/test.xls" : "data/test.xlsx")));
			//generate a new sheet:
			this.cSheet = this.workbook.createSheet();
			//write NUM_ROWS rows
			for (int i = 0; i < NUM_ROWS; i++) {
				Row r = this.cSheet.createRow(i);
				//write NUM_COLS columns
				for (int j = 0; j < NUM_COLS; j++) {
					Cell c = r.getCell(j);
					if (c == null) {
						c = r.createCell(j);
					c.setCellValue("TEST " + i + ":" + j);
		} catch (Exception e) {
			tbr = false;
		return tbr;
	public boolean Export(String filename) {
		boolean tbr = true;
		try {
			FileOutputStream out = new FileOutputStream(filename);
		} catch (Exception e) {
			tbr = false;
		return tbr;
	static public void main(String[] args) {
		long start;
		boolean didTest;
		ExcelTest et;
		System.out.println("Starting test...");
		start = System.currentTimeMillis();
		et = new ExcelTest(true);
		didTest = et.Test();
		if (didTest) {
		System.out.println("XLS (HSSF) version took " + (System.currentTimeMillis() - start) + " ms.");
		start = System.currentTimeMillis();
		et = new ExcelTest(false);
		didTest = et.Test();
		if (didTest) {
		System.out.println("XLSX (XSSF) version took " + (System.currentTimeMillis() - start) + " ms.");

Open in new window

You will notice that even for a relatively-small data set of 10k rows with 25 cols, the xls version takes ~2 seconds, while the xlsx version takes ~20 seconds.  Does anyone know how/if I can speed up POI's performance when working with large xlsx files?

Watch Question
This problem has been solved!
Unlock 1 Answer and 5 Comments.
See Answer
Why Experts Exchange?

Experts Exchange always has the answer, or at the least points me in the correct direction! It is like having another employee that is extremely experienced.

Jim Murphy
Programmer at Smart IT Solutions

When asked, what has been your best career decision?

Deciding to stick with EE.

Mohamed Asif
Technical Department Head

Being involved with EE helped me to grow personally and professionally.

Carl Webster
CTP, Sr Infrastructure Consultant

An Experts Exchange subscription includes unlimited access to online courses.

Get Started
Ask ANY Question

Connect with Certified Experts to gain insight and support on specific technology challenges including:

  • Troubleshooting
  • Research
  • Professional Opinions
Did You Know?

We've partnered with two important charities to provide clean water and computer science education to those who need it most. READ MORE