Convert Excel to CSV in Java with Apache POI & OpenCSV

Learn how to convert Excel files to CSV format in Java using Apache POI and OpenCSV libraries, covering basic file reading, manipulation, and writing techniques.
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How to Convert Excel Files to CSV Format Using Java

Converting Excel files to CSV format is a common requirement in software development when dealing with data import and export functionalities. Java provides robust tools and libraries to facilitate this conversion, notably Apache POI for handling Excel files and OpenCSV for creating and handling CSV files. This guide will guide you through the process of converting an Excel file (.xlsx or .xls) to a CSV file using these libraries.

Prerequisites
Before starting, ensure you have the following:

Java Development Kit (JDK) installed on your computer.

An Integrated Development Environment (IDE) such as Eclipse or IntelliJ IDEA.

Dependency management tool like Maven or Gradle.

Step 1: Set Up Your Project
First, set up a Java project and add the necessary dependencies. If you are using Maven, add the following dependencies to your pom.xml file:

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For Gradle, add the following in your build.gradle file:

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Step 2: Read the Excel File
Create a Java class and use Apache POI to read the Excel file. You can read both .xlsx and .xls formats using the WorkbookFactory class.

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Step 3: Convert Excel to CSV
Once the Excel file is read, iterate through the sheets and rows to construct CSV data. Use OpenCSV to handle the CSV creation.

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Step 4: Test Your Code
Finally, test your code to ensure it works correctly.

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Conclusion
Using Java to convert Excel files to CSV format is straightforward with libraries like Apache POI and OpenCSV. This solution scales well for both small and large datasets and can be integrated into larger Java applications dealing with data transformation and processing tasks.

By following these steps, you can seamlessly add Excel to CSV conversion functionality to your Java applications, enabling efficient data handling and manipulation for various business needs.