Prints out the total payment of a given payer for each month as well as the total paid/losses to a given vendor from a Paypal CSV file in the given user's currency and it uses the currency exchange rate for the day of the transaction. Good for taxes.

PaypalCSVReader.java

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import com.google.gson.JsonObject;
import com.google.gson.JsonParser;

import java.io.*;
import java.net.HttpURLConnection;
import java.net.URL;
import java.time.Month;
import java.util.Map;
import java.util.TreeMap;

public class PaypalCSVReader {

    // Get an API Key from: https://www.exchangerate-api.com/
    // Requires Pro account to access exchange rate history.
    private static final String API_KEY = "api_key";
    private static final String USER_CURRENCY_ID = "USD";

    public static void main(String[] args) {
        parsePaypalCSV(new File("").getAbsolutePath() + File.separator + "/src/main/resources/taxes.csv");
    }

    private static void parsePaypalCSV(String filePath) {
        try {
            String line;
            BufferedReader br = new BufferedReader(new FileReader(filePath));
            Map<Month, Map<String, Double>> totalsByPayerByMonth = new TreeMap<>();
            Map<Month, Map<String, Double>> lossesByVendorByMonth = new TreeMap<>();

            boolean skipFirstLine = false;
            while ((line = br.readLine()) != null) {
                String[] split = line.split("\",\"");
                if (!skipFirstLine) {
                    skipFirstLine = true;
                    continue;
                }
                int month = Integer.parseInt(split[0].substring(1, 3));
                Month month1 = Month.of(month);

                Map<String, Double> payerToTotal = totalsByPayerByMonth.computeIfAbsent(month1, payer -> new TreeMap<>());
                Map<String, Double> vendorToLosses = lossesByVendorByMonth.computeIfAbsent(month1, payment -> new TreeMap<>());

                String payer = split[3];

                String amount = split[7].replaceAll("\"", "");
                if (amount.isEmpty()) {
                    continue;
                }
                double total = Double.parseDouble(amount);
                String currencyID = split[6];

                double conversionRate = getConversionRate(currencyID, split[0]);
                double usdValue = total / conversionRate;
                if (total > 0) {
                    payerToTotal.put(payer, payerToTotal.getOrDefault(payer, 0D) + usdValue);
                } else {
                    vendorToLosses.put(payer, vendorToLosses.getOrDefault(payer, 0D) + usdValue);
                }
            }

            Gson GSON = new GsonBuilder().disableHtmlEscaping().setPrettyPrinting().create();

            String earnings = GSON.toJson(totalsByPayerByMonth);
            String losses = GSON.toJson(lossesByVendorByMonth);

            System.out.println("Earnings: \n" + earnings);
            System.out.println("\n");
            System.out.println("Losses: \n" + losses);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    private static double getConversionRate(String currencyID, String date) {
        if (currencyID.equals(USER_CURRENCY_ID)) {
            return 1;
        }
        String[] split = date.replaceAll("\"", "").split("/");
        try {
            URL url = new URL("https://v6.exchangerate-api.com/v6/" + API_KEY + "/history/" + USER_CURRENCY_ID + "/" + split[2] + "/" + split[0] + "/" + split[1]);
            HttpURLConnection request = (HttpURLConnection) url.openConnection();
            request.connect();
            JsonObject root = JsonParser.parseReader(new InputStreamReader((InputStream) request.getContent())).getAsJsonObject();
            JsonObject conversionRates = root.get("conversion_rates").getAsJsonObject();

            return conversionRates.get(currencyID).getAsDouble();
        } catch (IOException e) {
            throw new IllegalArgumentException();
        }
    }
}