How to Read Write Excel file in Java - POI Example

 To read and write Excel files in Java using the Apache POI library, you can follow these steps:

Add Apache POI dependencies: First, you need to include the Apache POI dependencies in your Java project. You can download the JAR files from the Apache POI website (poi.apache.org) or use a build tool like Maven or Gradle to manage the dependencies.

Create a new Java class and import the necessary classes:

java

Copy code

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

Reading an Excel file:

To read data from an existing Excel file, you can use the following code:

try {

    FileInputStream file = new FileInputStream("path/to/excel/file.xlsx");

    // Create Workbook instance for the Excel file

    Workbook workbook = new XSSFWorkbook(file);

    // Get the first sheet from the workbook

    Sheet sheet = workbook.getSheetAt(0);

    // Iterate over rows in the sheet

    for (Row row : sheet) {

        // Iterate over cells in the row

        for (Cell cell : row) {

            // Get the cell value and print it

            String cellValue = cell.getStringCellValue();

            System.out.println(cellValue);

        }

    }

    // Close the file

    file.close();

} catch (Exception e) {

    e.printStackTrace();

}

Writing to an Excel file:

To create a new Excel file or modify an existing one, you can use the following code:

try {

    // Create a new Workbook

    Workbook workbook = new XSSFWorkbook();

    // Create a new sheet

    Sheet sheet = workbook.createSheet("Sheet1");

    // Create a new row and set values

    Row row = sheet.createRow(0);

    Cell cell = row.createCell(0);

    cell.setCellValue("Hello");

    // Write the workbook to a file

    FileOutputStream file = new FileOutputStream("path/to/excel/file.xlsx");

    workbook.write(file);

    // Close the file

    file.close();

} catch (Exception e) {

    e.printStackTrace();

}

Make sure to replace "path/to/excel/file.xlsx" with the actual path to your Excel file.

These examples demonstrate the basic reading and writing operations using Apache POI. You can further explore the API documentation to work with more advanced features such as formatting, formulas, and multiple sheets within an Excel file.