A Comprehensive Guide to Reading and Writing CSV Files in Java

Introduction:

CSV (Comma-Separated Values) is a popular file format used for storing tabular data, where data values are separated by commas or other delimiters. It is commonly used for data exchange between different systems and is supported by many spreadsheet applications. In this blog post, we will explore how to read and write CSV files in Java, a versatile and widely-used programming language.

Reading CSV Files in Java:

To read CSV files in Java, we can use the built-in java.io package, which provides classes for reading and writing text files. Here's a step-by-step guide on how to read CSV files in Java:

        
            BufferedReader br = new BufferedReader(new FileReader("example.csv"));
            String line;
       		while ((line = br.readLine()) != null) {
            String[] fields = line.split(",");
        	}
        	br.close();
    
    

We can use the BufferedWriter class to write text to a character-output stream. We need to pass a FileWriter object to the BufferedWriter constructor, which represents the CSV file we want to write. Here's an example:

    
    BufferedWriter bw = new BufferedWriter(new FileWriter("example.csv"));
    bw.write("Field1,Field2,Field3");
	bw.newLine();
	bw.write("Value1,Value2,Value3");
    

Using a CSV Library - OpenCSV:

Now we will explore how to perform CSV file operations in Java using a CSV library. To begin, you need to add a CSV library to your Java project. There are several libraries available, such as OpenCSV, Apache Commons CSV, and Super CSV, that provide APIs for reading and writing CSV files. For this tutorial, we will use OpenCSV, a widely used and popular CSV library in Java.

You can add OpenCSV to your project by including the following Maven or Gradle dependency in your project's build file:

    
        <dependency>
            <groupId>com.opencsv</groupId>
            <artifactId>opencsv</artifactId>
            <version>5.5.2</version>
        </dependency>
    

Here's an example of how you can read a CSV file using OpenCSV:

    
        import com.opencsv.CSVReader;
        import java.io.FileReader;
        import java.io.IOException;

        public class CsvReaderExample {
            public static void main(String[] args) {
                String csvFile = "path/to/your/csv/file.csv";
                try (CSVReader reader = new CSVReader(new FileReader(csvFile))) {
                    String[] line;
                    while ((line = reader.readNext()) != null) {
                        // Process the CSV data
                        for (String data : line) {
                            System.out.print(data + " ");
                        }
                        System.out.println();
                    }
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    

Here's an example of how you can write data to a CSV file using OpenCSV:

    
        import com.opencsv.CSVWriter;
        import java.io.FileWriter;
        import java.io.IOException;

        public class CsvWriterExample {
            public static void main(String[] args) {
                String csvFile = "path/to/your/csv/file.csv";
                try (CSVWriter writer = new CSVWriter
            // Write data to the CSV file
            String[] data1 = {"ABC", "EFG", "30"};
            writer.writeNext(data1);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}