First of all, make sure that you have the Apache POI library included in your project. If you are using Maven, you can add the following to your pom.xml:
Maven Dependencies
<dependency>
<groupId>org.apache.poi</groupId>
<artifactId>poi-ooxml</artifactId>
<version>5.2.5</version>
</dependency>
Then, you can use the following code to create an Excel .xlsx file:
package org.kodejava.poi;
import org.apache.poi.ss.usermodel.*;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;
import java.io.FileOutputStream;
import java.io.IOException;
public class ExcelExample {
public static void main(String[] args) {
// Create a new Workbook
Workbook workbook = new XSSFWorkbook();
// Create a new sheet in the workbook with a name
Sheet sheet = workbook.createSheet("MySheet");
// Create a row at index 0
Row row = sheet.createRow(0);
// Create a cell at index 0
Cell cell = row.createCell(0, CellType.STRING);
// Assign the string "Hello" to the cell
cell.setCellValue("Hello");
// Add some other rows and cells similarly...
// ...
try (FileOutputStream fos = new FileOutputStream("MyExcel.xlsx")) {
workbook.write(fos);
} catch (IOException e) {
e.printStackTrace();
}
System.out.println("Excel file has been generated!");
try {
workbook.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
This program will create an Excel .xlsx file named MyExcel.xlsx with a single sheet called “MySheet.” The sheet has a single cell in the first row which contains the string “Hello.” The output file will be generated in the root directory of your project.
The above-given code is only a basic example. Apache POI allows advanced features like applying styles to cells, merging cells, and working with formulas among others. The library also supports other Microsoft Office file formats.
Here is another slightly more complex example where we create multiple rows and cells:
package org.kodejava.poi;
import org.apache.poi.ss.usermodel.*;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;
import java.io.FileOutputStream;
import java.io.IOException;
public class ExcelAnotherExample {
public static void main(String[] args) {
Workbook workbook = new XSSFWorkbook();
Sheet sheet = workbook.createSheet("Students");
Row rowHeader = sheet.createRow(0);
Cell cellHeader1 = rowHeader.createCell(0, CellType.STRING);
cellHeader1.setCellValue("ID");
Cell cellHeader2 = rowHeader.createCell(1, CellType.STRING);
cellHeader2.setCellValue("Name");
for(int i = 1; i < 6; i++) {
Row rowData = sheet.createRow(i);
Cell cellData1 = rowData.createCell(0, CellType.NUMERIC);
cellData1.setCellValue(i);
Cell cellData2 = rowData.createCell(1, CellType.STRING);
cellData2.setCellValue("Student " + i);
}
try (FileOutputStream fos = new FileOutputStream("StudentsData.xlsx")) {
workbook.write(fos);
} catch (IOException e) {
e.printStackTrace();
}
System.out.println("Excel file has been generated!");
try {
workbook.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
This code creates an Excel file named StudentsData.xlsx with a single worksheet. The worksheet contains a listing of student names and their respective IDs. The first row is a header with “ID” and “Name” labels. The next rows contain the IDs (numeric) and names (string “Student X”) for five different students.