Java Program to Read a CSV File and Calculate the Total

CSV files are everywhere. This program reads a small sales file, skips the header, ignores bad lines, and shows the total and the average.

Program

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.util.List;

public class Main {
    record Sale(String item, int quantity, double price) {
        double amount() { return quantity * price; }
    }

    public static void main(String[] args) throws IOException {
        Path file = Path.of("sales.csv");
        Files.write(file, List.of(
                "item,quantity,price",
                "Pen,10,5.50",
                "Book,2,250",
                "Bag,1,899.99",
                "Broken line",
                "Notebook,abc,40"));

        List<Sale> sales = Files.readAllLines(file).stream()
                .skip(1)                                   // header
                .map(Main::parse)
                .filter(s -> s != null)
                .toList();

        double total = sales.stream().mapToDouble(Sale::amount).sum();
        System.out.println("Valid rows: " + sales.size());
        sales.forEach(s -> System.out.printf("%-10s %8.2f%n", s.item(), s.amount()));
        System.out.printf("Total: %.2f%n", total);
        System.out.printf("Average per row: %.2f%n", total / sales.size());
    }

    static Sale parse(String line) {
        String[] p = line.split(",");
        if (p.length != 3) {
            System.out.println("Skipped (wrong columns): " + line);
            return null;
        }
        try {
            return new Sale(p[0].trim(), Integer.parseInt(p[1].trim()), Double.parseDouble(p[2].trim()));
        } catch (NumberFormatException e) {
            System.out.println("Skipped (bad number): " + line);
            return null;
        }
    }
}

Notes

• split(",") is fine for simple files. If a value can contain a comma inside quotes, use a CSV library such as Apache Commons CSV.
• We use a record for a row, and a stream to process the lines. See Java Records and Java Streams.
• For huge files, use Files.lines() in a try with resources and process one line at a time. See Java File Handling.

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