XYZ CODE: Create and manage date-based and time-based events including a combination of date and time into a single object using LocalDate, LocalTime, LocalDateTime, Instant, Period, and Duration

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OCAJP has a topic similar to this one, here only ZonedDateTime, Duration and Instant are new to OCPJP.

ZonedDateTime

java.time package has 4 type of date-based and time-based classes:

Local Date. Contains date - no time and time zone.
LocalTime. Contains time - no date and timezone.
LocalDateTime. Contains date and time - no timezone.
ZonedDateTime. Contains date, time and time zone.

The first 3 we have visited in OCAJP, the 4th one is new. Before telephone is invented, everybody knows "Let's meet again today afternoon at 3" means, because you are talking with a local folk in front of your face. At internet era, you need to be careful who are you talking to -- the guy might be talking to you with skype in India. Where your afternoon is his midnight. In that case, you have to additionally mention the time zone.

OCPJP>cat ZonedDateTimeExample.java

import java.time.LocalDate;

import java.time.LocalDateTime;

import java.time.LocalTime;

import java.time.ZoneId;

import java.time.ZonedDateTime;

import java.time.format.DateTimeFormatter;

public class ZonedDateTimeExample {

public static void main(String[] args) {

ZoneId zoneId = ZoneId.of("US/Eastern");

LocalDate localDate = LocalDate.of(2017, 2, 2);

LocalTime localTime = LocalTime.of(10, 10, 10);

LocalDateTime localDateTime = LocalDateTime.of(localDate, localTime);

ZonedDateTime zonedDateTime = ZonedDateTime.of(localDateTime, zoneId);

System.out.println(zonedDateTime.format(DateTimeFormatter.ISO_ZONED_DATE_TIME));

//zonedDateTime = ZonedDateTime.of(2017, 2, 2, 10, 10, 10, zoneId); //don't compile

zonedDateTime = ZonedDateTime.of(2017, 2, 2, 10, 10, 10, 10, zoneId);

System.out.println(zonedDateTime.format(DateTimeFormatter.ISO_ZONED_DATE_TIME));

System.out.println(

ZonedDateTime.of(localDate, localTime, ZoneId.of("US/Eastern"))

.format(DateTimeFormatter.ISO_ZONED_DATE_TIME));

}

OCPJP>

OCPJP>javac ZonedDateTimeExample.java

OCPJP>java ZonedDateTimeExample

2017-02-02T10:10:10-05:00[US/Eastern]

2017-02-02T10:10:10.00000001-05:00[US/Eastern]

2017-02-02T10:10:10-05:00[US/Eastern]

OCPJP>

While a Period is a day or more of time, Duration is intended for smaller units of time. The Duration can additionally store hours, minutes and seconds, Millisecond, Nanoseconds.

OCPJP>cat DurationExample.java

import java.time.Duration;

import java.time.LocalDate;

import java.time.LocalDateTime;

import java.time.LocalTime;

import java.time.Period;

import java.time.ZoneId;

import java.time.ZonedDateTime;

import java.time.temporal.ChronoUnit;

public class DurationExample {

public static void main(String...args) {

LocalDate localDate = LocalDate.of(2017, 1, 1);

LocalTime localTime = LocalTime.of(1, 1);

LocalDateTime localDateTime = LocalDateTime.of(localDate, localTime);

ZonedDateTime zonedDateTime = ZonedDateTime.of(localDateTime, ZoneId.of("US/Eastern"));

System.out.println("Period.of");

Period period = Period.of(1, 1, 1);

//Exception in thread "main" java.time.temporal.UnsupportedTemporalTypeException: Unsupported unit: Months

//System.out.println(localTime.plus(period));

System.out.println(localDate.plus(period));

System.out.println(localDateTime.plus(period));

System.out.println(zonedDateTime.plus(period));

System.out.println("Duration.ofDays");

Duration duration = Duration.ofDays(1);

//Exception in thread "main" java.time.temporal.UnsupportedTemporalTypeException: Unsupported unit: Seconds

//System.out.println(localDate.plus(duration));

System.out.println(localTime.plus(duration));

System.out.println(localDateTime.plus(duration));

System.out.println(zonedDateTime.plus(duration));

System.out.println(localDateTime.plus(Duration.of(1, ChronoUnit.DAYS)));

System.out.println("Duration.ofHours");

System.out.println(localDateTime.plus(Duration.ofHours(1)));

System.out.println(localDateTime.plus(Duration.of(1, ChronoUnit.HOURS)));

System.out.println("Duration.ofMinutes");

System.out.println(localDateTime.plus(Duration.ofMinutes(1)));

System.out.println(localDateTime.plus(Duration.of(1, ChronoUnit.MINUTES)));

System.out.println("Duration.ofSeconds");

System.out.println(localDateTime.plus(Duration.ofSeconds(1)));

System.out.println(localDateTime.plus(Duration.of(1, ChronoUnit.SECONDS)));

System.out.println("Duration.ofMillis");

System.out.println(localDateTime.plus(Duration.ofMillis(1)));

System.out.println(localDateTime.plus(Duration.of(1, ChronoUnit.MILLIS)));

System.out.println("Duration.ofNanos");

System.out.println(localDateTime.plus(Duration.ofNanos(1)));

System.out.println(localDateTime.plus(Duration.of(1, ChronoUnit.NANOS)));

}

OCPJP>

OCPJP>javac DurationExample.java

OCPJP>java DurationExample

Period.of

2018-02-02

2018-02-02T01:01

2018-02-02T01:01-05:00[US/Eastern]

Duration.ofDays

01:01

2017-01-02T01:01

2017-01-02T01:01-05:00[US/Eastern]

2017-01-02T01:01

Duration.ofHours

2017-01-01T02:01

Duration.ofMinutes

2017-01-01T01:02

Duration.ofSeconds

2017-01-01T01:01:01

Duration.ofMillis

2017-01-01T01:01:00.001

Duration.ofNanos

2017-01-01T01:01:00.000000001

OCPJP>

The Instant class represents a specific moments in time in the GMT time zone.

OCPJP>cat InstantsDemo.java

import java.time.Duration;

import java.time.Instant;

import java.time.LocalDate;

import java.time.LocalTime;

import java.time.ZoneId;

import java.time.ZonedDateTime;

import java.time.temporal.ChronoUnit;

public class InstantsDemo {

public static void main(String...args) {

LocalDate localDate = LocalDate.of(2017, 1, 1);

LocalTime localTime = LocalTime.of(1, 1);

ZonedDateTime zonedDateTime = ZonedDateTime.of(localDate, localTime, ZoneId.of("US/Eastern") );

System.out.println(zonedDateTime);

System.out.println(zonedDateTime.toInstant());

System.out.println(Instant.ofEpochMilli(0));

Duration duration = Duration.between(Instant.now(), zonedDateTime.toInstant());

System.out.println(duration.toDays());

Instant nextDay = Instant.now().plus(1, ChronoUnit.DAYS);

System.out.println(nextDay);

System.out.println(Instant.now().plus(1, ChronoUnit.HOURS));

System.out.println(Instant.now().plus(1, ChronoUnit.WEEKS));

}

OCPJP>

OCPJP>javac InstantsDemo.java

OCPJP>java InstantsDemo

2017-01-01T01:01-05:00[US/Eastern]

2017-01-01T06:01:00Z

1970-01-01T00:00:00Z

-305

2017-11-04T01:56:41.188Z

2017-11-03T02:56:41.188Z

Exception in thread "main" java.time.temporal.UnsupportedTemporalTypeException: Unsupported unit: Weeks

at java.time.Instant.plus(Instant.java:862)

at InstantsDemo.main(InstantsDemo.java:25)

OCPJP>