Java 8 Time Package and Locale

java-8-time-package-and-locale

Java 8 provides an extensive time computational package - java.time that is recommended for any new code to use because it provides so many helper methods to compute time and easily used with java.util.Locale class to support localization (l10n) and internationalization (i18n). In this article, we will learn some most useful operations using the java.time package with java.util.Locale class through a scenario of Beijing Winter Olympic Game opening day reminder.

Something to know: China only use one timezone which is standardized as China Standard Time (CST). Shanghai and Beijing thus use the same time.

import java.time.*;
import java.time.format.*;
import java.time.temporal.*;
import java.util.Locale;

public class WinterOlympicGames {
    public static void main(String... args) {
        LocalDate nowDate = LocalDate.now();
        LocalTime nowTime = LocalTime.now();
        LocalDateTime nowDateTime = LocalDateTime.of(nowDate, nowTime);
        System.out.println("It's currently " + nowDateTime + " where I am");

        LocalDate openDate1 = LocalDate.of(2018, 2, 9);
        LocalDate openDate2 = LocalDate.parse("2018-02-09");
        System.out.println("Opening date: " + openDate1 + ", " + openDate2);

        // Local time in PyeongChang
        LocalTime begins = LocalTime.of(19, 0, 0);
        LocalTime torchLighting = LocalTime.of(20, 30, 15);
        System.out.println("Opening begins at " + begins + 
            " and torch lighting is at " + torchLighting);

        String openingDateTime = "2018-02-09 19:00";
        DateTimeFormatter formatter = 
            DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm");
        LocalDateTime openingDay = 
            LocalDateTime.parse(openingDateTime, formatter);
        System.out.println("Opening day: " + openingDay);
        System.out.println("Opening day, formatted: " + 
            openingDay.format(
                DateTimeFormatter.ofPattern("MM/dd/yyyy HH:mm")));
        System.out.println("China time: " + openingDay.minusHours(1));
        System.out.println("Time of Departure from PyeongChang to China: " 
            + openingDay.plusDays(3));
        System.out.println("What day of the week is the opening day? " 
            + openingDay.getDayOfWeek());

        // // Get a list of Zone Ids:
        // ZoneId.getAvailableZoneIds()
        //  .stream()
        //  .sorted()
        //  .filter(x -> x.contains("Asia"))
        //  .forEach(x -> System.out.println(x));

        ZonedDateTime zOpeningDateTime = 
            ZonedDateTime.of(openingDay, ZoneId.of("Asia/Seoul"));
        System.out.println("Date and time opening begins with time zone: " 
            + zOpeningDateTime);


        ZoneId pyeongChang = ZoneId.of("Asia/Seoul");
        // pyeongChang.getRules() returns a ZoneRules object that has all the
        // rules about time zones, including daylight savings and standard 
        // time.
        System.out.println("Is Daylight Savings in effect at time of " 
            + "opending day in PyeongChang? " 
            + pyeongChang.getRules()
                .isDaylightSavings(zOpeningDateTime.toInstant()));

        ZonedDateTime followingSundayDayTime = 
            zOpeningDateTime.with(
                TemporalAdjusters.next(DayOfWeek.SUNDAY));
        System.out.println("Sunday following the opending day: " 
            + followingSundayDayTime);


        // Next Winter Olympic Games
        ZonedDateTime  zOpeningBeijing = 
            ZonedDateTime.of(2022, 2, 4, 20, 0, 0, 0, 
                ZoneId.of("Asia/Shanghai"));
        System.out.println("Next Winter Olympic Games in Beijing, " 
            + "date/time in Beijing: " + zOpeningBeijing);

        Period period = Period.ofMonths(1);
        System.out.println("Period is " + period);
        ZonedDateTime reminder = zOpeningBeijing.minus(period);
        System.out.println("DateTime of 1 month reminder: " + reminder);

        System.out.println("Local DateTime (Beijing) of reminder: " 
            + reminder.toLocalDateTime());

        // Notice the its winter standard time in Ohio, hence 13 hours offset.
        System.out.println("Zoned DateTime (Ohio) of reminder: " 
            + reminder.withZoneSameInstant(ZoneId.of("US/Eastern")));

        // Local in Beijing
        begins = LocalTime.of(20, 0, 0);
        torchLighting = LocalTime.of(22, 10, 12);
        System.out.println("Opening begins at " + begins 
            + " and torch lighting is at " + torchLighting);

        long betweenMins = ChronoUnit.MINUTES.between(begins, torchLighting);
        System.out.println("Minutes between begin and and torch lighting: " 
            + betweenMins);

        Duration betweenDuration = Duration.ofMinutes(betweenMins);
        System.out.println("Duration: " + betweenDuration);

        LocalTime torchLightingBegins = begins.plus(betweenDuration);
        System.out.println("Torching Lighting begins, computed: " 
            + torchLightingBegins);

        // GMT
        zOpeningBeijing = 
            ZonedDateTime.of(2022, 2, 4, 20, 0, 0, 0, 
                ZoneId.of("Asia/Shanghai"));
        Instant openingBeijingInstant = zOpeningBeijing.toInstant();
        System.out.println("Beijing's opening day instant is: " 
            + openingBeijingInstant);

        Instant nowInstant = Instant.now();
        openingBeijingInstant = zOpeningBeijing.toInstant();
        long minsBetween = 
            ChronoUnit.MINUTES.between(nowInstant, openingBeijingInstant);
        Duration durationBetweenInstants = Duration.ofMinutes(minsBetween);
        System.out.println("Minutes between " + minsBetween
            + ", is duration " + durationBetweenInstants);

        long daysBetween = 
            ChronoUnit.DAYS.between(nowInstant, openingBeijingInstant);
        Period periodBetweenInstants = Period.ofDays((int)daysBetween);
        System.out.println("Days between " + daysBetween
            + ", is period " + periodBetweenInstants);

        Instant now = Instant.now();
        System.out.println("Seconds since epoch: " + now.getEpochSecond());

        System.out.println("DateTime of 3-day remnder: " 
            + zOpeningBeijing.minus(Period.ofDays(3)));
        System.out.println("Day of week for 3-day reminder: " 
            + zOpeningBeijing.minus(Period.ofDays(3)).getDayOfWeek());

        ZonedDateTime zOhio = 
            zOpeningBeijing.withZoneSameInstant(ZoneId.of("US/Eastern"));
        System.out.println("Beijing Opening begins at " 
            + zOhio + " US Eastern time");
        System.out.println("Call frinds in China 1 hour before opening: " 
            + zOhio.minusHours(1) + ", " 
            + zOpeningBeijing.minusHours(1) + " Beijing time");

        System.out.println("Is Beijing Winter Olympic Games still in the" 
            + " future? " + ZonedDateTime.now().isBefore(zOpeningBeijing));

        System.out.println("Is 2022 a leap year? " 
            + zOpeningBeijing.toLocalDate().isLeapYear());
        System.out.println("Is 2022 a leap year? " + Year.of(2022).isLeap());

        System.out.println("Opening date/time written for Frinds in Ohio: " 
            + zOhio.format(
                DateTimeFormatter.ofPattern("MM/dd/yyyy hh:mm a")));

        System.out.println("Opening date/time in China Locale: "
            + zOpeningBeijing.format(
                DateTimeFormatter.ofLocalizedDateTime(FormatStyle.SHORT)
                    .withLocale(Locale.CHINA)));

        // Usage with Locale
        Locale myLocale = Locale.getDefault();
        System.out.println("My locale: " + myLocale);
        LocalDateTime aDateTime = LocalDateTime.of(2022, 2, 4, 20, 0, 0);
        System.out.println("The date and time: "
            + aDateTime.format(
                DateTimeFormatter.ofLocalizedDateTime(FormatStyle.SHORT)));
        ZonedDateTime zDateTime = 
            ZonedDateTime.of(aDateTime, ZoneId.of("Asia/Shanghai"));
        Locale locZH = new Locale("zh"); // Chinese
        Locale locCN = new Locale("zh", "CN"); // Chinese, China
        Locale locUK = new Locale("en", "UK"); // English, UK
        System.out.println("China (LONG) "
            + zDateTime.format(
                DateTimeFormatter.ofLocalizedDateTime(FormatStyle.LONG)
                    .withLocale(locCN)));
        System.out.println("UK (LONG) "
            + zDateTime.format(
                DateTimeFormatter.ofLocalizedDateTime(FormatStyle.LONG)
                    .withLocale(locUK)));
        System.out.println("China, country: " + locCN.getDisplayCountry());
        System.out.println("China, country, local: " 
            + locCN.getDisplayCountry(locCN));
        System.out.println("UK, country: " + locUK.getDisplayCountry());
        // fallback to English when there is no Chinese name for UK
        System.out.println("UK, country, local in China: " 
            + locUK.getDisplayCountry(locCN)); 
    }
}

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