WeatherNowの祝日CSV生成用コード

HolidayConverter.java

package jp.noxi.weathernow;

import java.io.*;
import java.net.HttpURLConnection;
import java.net.URL;
import java.nio.file.Files;
import java.time.LocalDate;
import java.time.format.DateTimeFormatter;
import java.util.ArrayList;
import java.util.List;

public class HolidayConverter {

    public static void main(String... args) throws Exception {
        String exportName = args.length != 0 ? args[0] : "holiday.csv";
        new HolidayConverter(exportName).execute();
    }


    private static final String HOLIDAY_ICAL_URL = "https://calendar.google.com/calendar/ical/ja.japanese%23holiday%40group.v.calendar.google.com/public/basic.ics";
    private static final DateTimeFormatter PARSE_FORMATTER = DateTimeFormatter.ofPattern("yyyyMMdd");

    private final String exportName;

    public HolidayConverter(String exportName) {
        this.exportName = exportName;
    }

    public void execute() throws Exception {
        URL url = new URL(HOLIDAY_ICAL_URL);
        HttpURLConnection conn = (HttpURLConnection) url.openConnection();
        try (InputStream in = conn.getInputStream();
             BufferedReader reader = new BufferedReader(new InputStreamReader(in))) {

            List<Holiday> holidays = new ArrayList<>();
            Holiday holiday = null;
            String s;
            while ((s = reader.readLine()) != null) {
                if (s.startsWith("DTSTART")) {
                    s = s.replace("DTSTART;VALUE=DATE:", "");
                    holiday = new Holiday();
                    holiday.date = LocalDate.parse(s, PARSE_FORMATTER);
                    continue;
                }

                if (s.startsWith("SUMMARY") && holiday != null) {
                    s = s.replace("SUMMARY:", "");
                    holiday.name = s;
                    holidays.add(holiday);
                    holiday = null;
                    continue;
                }
            }

            holidays.sort((s1, s2) -> s1.date.compareTo(s2.date));

            try (BufferedWriter writer = Files.newBufferedWriter(new File(exportName).toPath())) {
                holidays.forEach(h -> {
                    try {
                        writer.write(h.toString());
                        writer.newLine();
                    } catch (IOException e) {
                        throw new UncheckedIOException(e);
                    }
                });
            }
        } finally {
            conn.disconnect();
        }
    }

}

class Holiday {
    private static final DateTimeFormatter FORMATTER = DateTimeFormatter.ofPattern("yyyy/MM/dd");

    String name;
    LocalDate date;

    @Override
    public String toString() {
        return date.format(FORMATTER) + "," + name;
    }
}