Two ways to do this,

• Using core Java
• Using OpenCSV

Let’s start with the core Java way.

Using core Java

Write content to the CSV file.

  public void writeContentToCSVFile() throws IOException {

            List<List<String>> rows = Arrays.asList(
                    Arrays.asList("Learn Node.js", "Andrew", "programming Tutorial"),
                    Arrays.asList("Learn Scala", "Andrew", "programming Tutorial")

            );

            FileWriter csvWriter = new FileWriter("book.csv");
            csvWriter.append("Name");
            csvWriter.append(",");
            csvWriter.append("Author");
            csvWriter.append(",");
            csvWriter.append("Category");
            csvWriter.append("\n");

            for (List<String> rowData : rows) {
                csvWriter.append(String.join(",", rowData));
                csvWriter.append("\n");
            }
            csvWriter.close();
    }

Output

Read content from the CSV file

 public void readContentFromCSVFile() throws IOException {
        try (BufferedReader input = new BufferedReader(new FileReader("book.csv"))) {
            String row;
            while ((row = input.readLine()) != null) {
                String[] data = row.split(",");
                for (int i = 0; i < data.length; i++) {
                    String comma = (i + 1 == data.length ? "" : ",");
                    System.out.print(data[i] + comma);
                }
                System.out.println();
            }
        }
    }

Output

Name,Author,Category
Learn Node.js,Andrew,programming Tutorial
Learn Scala,Andrew,programming Tutorial

Using OpenCSV

        <dependency>
            <groupId>com.opencsv</groupId>
            <artifactId>opencsv</artifactId>
            <version>4.6</version>
        </dependency>

package csvdemo;

import com.opencsv.CSVReader;

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

public class OpenCsvDemo {
    public static void main(String[] args) throws IOException {
        CSVReader csvReader = new CSVReader(new FileReader("book.csv"));
        List<String[]> list = new ArrayList<>();

        String[] line;
        while ((line = csvReader.readNext()) != null) {
            for (int i = 0; i < line.length; i++) {
                String comma = (i + 1 == line.length ? "" : ",");
                System.out.print(line[i] + comma);

            }
            System.out.println();
            list.add(line);
        }
        csvReader.close();
    }
}

Write content to CSV file Using OpenCSV

public void writeToCsvFile() throws IOException {
        try (
                Writer writer = Files.newBufferedWriter(Paths.get("contact.csv"));

                CSVWriter csvWriter = new CSVWriter(writer,
                        CSVWriter.DEFAULT_SEPARATOR,
                        CSVWriter.NO_QUOTE_CHARACTER,
                        CSVWriter.DEFAULT_ESCAPE_CHARACTER,
                        CSVWriter.DEFAULT_LINE_END);
        ) {
            String[] headerRecord = {"Name", "Email", "Phone", "Country"};
            csvWriter.writeNext(headerRecord);

            csvWriter.writeNext(new String[]{"Sundar Pichai ♥", "sundar.pichai@gmail.com", "+1-1111111111", "India"});
            csvWriter.writeNext(new String[]{"Satya Nadella", "satya.nadella@outlook.com", "+1-1111111112", "India"});
        }
    }

Output

Name,Email,Phone,Country
Sundar Pichai ♥,sundar.pichai@gmail.com,+1-1111111111,India
Satya Nadella,satya.nadella@outlook.com,+1-1111111112,India

Read content from CSV file Using OpenCSV

 public void readFromCsvFile() throws IOException {
        CSVReader csvReader = new CSVReader(new FileReader("contact.csv"));
        List<String[]> list = new ArrayList<>();

        String[] line;
        while ((line = csvReader.readNext()) != null) {
            for (int i = 0; i < line.length; i++) {
                String comma = (i + 1 == line.length ? "" : ",");
                System.out.print(line[i] + comma);

            }
            System.out.println();
            list.add(line);
        }
        csvReader.close();
    }

Source Code

https://github.com/AndrewProgramming/LearnJavaByExample