Working with CSV in Java: OpenCSV and Apache Commons CSV Libraries

Working with CSV in Java: OpenCSV and Apache Commons CSV

CSV (Comma-Separated Values) is one of the most common formats for storing and exchanging tabular data. Java does not have a built-in library for convenient CSV handling (only manual parsing via BufferedReader), so developers use third-party tools. In this article, we will look at two popular libraries: OpenCSV and Apache Commons CSV. You will learn how to read, write, and process CSV files with code examples.

1. OpenCSV: Lightweight Parsing and Annotations

OpenCSV is a simple and efficient library for working with CSV. It supports line-by-line reading, mapping to Java objects (via @CsvBindByName annotations), as well as data writing.

Adding Dependency (Maven)

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

Reading CSV into a List of Strings

import com.opencsv.CSVReader;import java.io.FileReader;import java.util.List;

public class OpenCsvExample {    public static void main(String[] args) throws Exception {        try (CSVReader reader = new CSVReader(new FileReader("data.csv"))) {            List<String[]> rows = reader.readAll();            for (String[] row : rows) {                System.out.println(String.join(" | ", row));            }        }    }}

Mapping to a Java Object

import com.opencsv.bean.CsvBindByName;import com.opencsv.bean.CsvToBean;import com.opencsv.bean.CsvToBeanBuilder;import java.io.FileReader;import java.util.List;

public class User {    @CsvBindByName(column = "name")    private String name;

    @CsvBindByName(column = "email")    private String email;

    // getters and setters}

// Readingtry (FileReader reader = new FileReader("users.csv")) {    CsvToBean<User> csvToBean = new CsvToBeanBuilder<User>(reader)            .withType(User.class)            .withIgnoreLeadingWhiteSpace(true)            .build();    List<User> users = csvToBean.parse();    users.forEach(u -> System.out.println(u.getName() + " - " + u.getEmail()));}

Writing CSV

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

try (CSVWriter writer = new CSVWriter(new FileWriter("output.csv"))) {    String[] header = {"Name", "Age", "City"};    writer.writeNext(header);    writer.writeNext(new String[]{"Alice", "30", "Moscow"});    writer.writeNext(new String[]{"Bob", "25", "SPb"});}

2. Apache Commons CSV: Flexibility and Performance

Apache Commons CSV is part of the Apache Commons ecosystem. It features high performance, support for different formats (CSV, TSV, Excel), and customizable delimiters.

Adding Dependency (Maven)

<dependency>    <groupId>org.apache.commons</groupId>    <artifactId>commons-csv</artifactId>    <version>1.11.0</version></dependency>

Reading CSV with Headers

import org.apache.commons.csv.CSVFormat;import org.apache.commons.csv.CSVParser;import org.apache.commons.csv.CSVRecord;import java.io.FileReader;import java.io.Reader;

try (Reader in = new FileReader("data.csv");     CSVParser parser = CSVFormat.DEFAULT             .withFirstRecordAsHeader()             .parse(in)) {    for (CSVRecord record : parser) {        String name = record.get("name");        String email = record.get("email");        System.out.println(name + " : " + email);    }}

Writing CSV with Custom Delimiter

import org.apache.commons.csv.CSVFormat;import org.apache.commons.csv.CSVPrinter;import java.io.FileWriter;import