Working with CSV in Java: A Complete Guide to Reading and Writing

Working with CSV in Java: A Complete Guide

CSV (Comma-Separated Values) is one of the most popular formats for storing and exchanging tabular data. In Java, there are several ways to work with CSV files: from manual parsing to using specialized libraries. In this article, we will cover the main approaches, including standard Java tools and popular third-party libraries.

1. Standard Approach: Manual CSV Reading

For simple projects, you can do without third-party libraries. Use BufferedReader and String.split():

import java.io.BufferedReader;import java.io.FileReader;import java.io.IOException;import java.util.ArrayList;import java.util.List;

public class SimpleCSVReader {    public static List<String[]> readCSV(String filePath) {        List<String[]> rows = new ArrayList<>();        String line;                try (BufferedReader br = new BufferedReader(new FileReader(filePath))) {            while ((line = br.readLine()) != null) {                String[] values = line.split(",");                rows.add(values);            }        } catch (IOException e) {            e.printStackTrace();        }        return rows;    }        public static void main(String[] args) {        List<String[]> data = readCSV("data.csv");        for (String[] row : data) {            System.out.println(String.join(" | ", row));        }    }}

Disadvantages: does not handle quotes, escaping of commas within fields, or line breaks. For production, it's better to use libraries.

2. OpenCSV — Powerful and Simple Library

OpenCSV is one of the most popular libraries for working with CSV in Java. It solves all parsing issues: quotes, escaping, different delimiters.

Installation (Maven):

<dependency>    <groupId>com.opencsv</groupId>    <artifactId>opencsv</artifactId>    <version>5.9</version></dependency>

Reading CSV with OpenCSV:

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

public class OpenCSVReader {    public static void main(String[] args) {        try (CSVReader reader = new CSVReader(new FileReader("data.csv"))) {            String[] nextLine;            while ((nextLine = reader.readNext()) != null) {                System.out.println(String.join(" | ", nextLine));            }        } catch (IOException | CsvValidationException e) {            e.printStackTrace();        }    }}

Writing CSV with OpenCSV:

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

public class OpenCSVWriter {    public static void main(String[] args) {        String[] header = {"Name", "Age", "Email"};        String[] row1 = {"Alice", "30", "alice@example.com"};        String[] row2 = {"Bob", "25", "bob@example.com"};                try (CSVWriter writer = new CSVWriter(new FileWriter("output.csv"))) {            writer.writeNext(header);            writer.writeNext(row1);            writer.writeNext(row2);        } catch (IOException e) {            e.printStackTrace();        }    }}

3. Apache Commons CSV — Flexibility and Performance

Apache Commons CSV is another powerful library with support for different formats (CSV, TSV, Excel).

Installation (Maven):

<dependency>    <groupId>org.apache.commons</groupId>    <artifactId>commons-csv</artifactId>    <ver