Working with Excel in Java: Apache POI and Alternatives

Working with Excel in Java: Library Overview and Practical Examples

In corporate Java development, there is often a need to programmatically create, read, and modify Excel spreadsheets. This can include generating reports, importing data from external systems, or exporting calculation results. In this article, we will review the main libraries for working with Excel in Java, their features, and provide clear code examples.

Why Java, not Python?

Despite our website being called PythonLib, Java remains one of the most popular languages for enterprise development. Many companies actively use Java for server-side applications, and integration with Excel is a common requirement. Understanding how to work with Excel in Java will be useful for both beginner and experienced developers.

Main Libraries for Working with Excel in Java

There are several mature libraries, each with its own strengths:

• Apache POI — the most popular and feature-rich library. Supports .xls (HSSF) and .xlsx (XSSF) formats. Allows creating, reading, and modifying files, supports formulas, styles, and charts.
• JExcelApi (jxl) — a lighter library that only supports the old .xls format. Suitable for simple tasks, but has not been developed since 2009.
• Apache POI + XSSF/SXSSF — advanced capabilities for working with large files. SXSSF (Streaming) allows processing millions of rows with low memory consumption.
• Docx4j — a library for working with Office Open XML, can be used for .xlsx, but is more commonly used for Word.

Getting Started with Apache POI

To add the library to a Maven project, add the following dependencies to pom.xml:

<!-- For working with .xls (HSSF) --><dependency>    <groupId>org.apache.poi</groupId>    <artifactId>poi</artifactId>    <version>5.2.5</version></dependency>

<!-- For working with .xlsx (XSSF) --><dependency>    <groupId>org.apache.poi</groupId>    <artifactId>poi-ooxml</artifactId>    <version>5.2.5</version></dependency>

If you use Gradle, add the lines to build.gradle:

implementation 'org.apache.poi:poi:5.2.5'implementation 'org.apache.poi:poi-ooxml:5.2.5'

Example: Creating an Excel File with a Table

Let's look at a simple example of creating a .xlsx file with employee data.

import org.apache.poi.ss.usermodel.*;import org.apache.poi.xssf.usermodel.XSSFWorkbook;import java.io.FileOutputStream;import java.io.IOException;

public class ExcelWriter {    public static void main(String[] args) {        // Create a new workbook        try (Workbook workbook = new XSSFWorkbook()) {            // Create a sheet            Sheet sheet = workbook.createSheet("Employees");

            // Create a header row            Row headerRow = sheet.createRow(0);            String[] columns = {"ID", "Name", "Position", "Salary"};            for (int i = 0; i < columns.length; i++) {                Cell cell = headerRow.createCell(i);                cell.setCellValue(columns[i]);                // Make the header bold                CellStyle style = workbook.createCellStyle();                Font font = workbook.createFont();                font.setBold(true);                style.setFont(font);                cell.setCellStyle(style);            }

            // Fill with data            Object[][] data = {                {1, "Ivan Ivanov", "Developer", 150000},                {2, "Petr Petrov", "Analyst", 120000},                {3, "Sidor Sidorov", "Manager", 180000}