Java 8 – Instant with method details and examples

June 29, 2022 SJ Java 8, Java 8 Date/Time 0

In this article, we will discuss about newly introduced Instant class in Java 1.8 version for dealing with date/time information in program with ease and convenience which captures instantaneous moment in UTC/GMT or in other words current date/time in UTC/GMT

Prior to introducing LocalDate, LocalTime, LocalDateTime, ZonedDateTime, OffsetDateTime and Instant under java.time.*; package in Java 1.8 version, we have to deal with java.util.Date, java.util.Calendar, java.sql.Timestamp, java.sql.Time, java.util.TimeZone, System.currentTimeMillis() for date/time handling along with Offset/Zone in Java which isn’t easy & straight-forward and there are few issues as mentioned below,

  • Thread-safety :- Existing Date/Time classes and its methods aren’t thread-safe and hence it’s not convenient to handle in concurrent/parallel environment
  • Not so-easy API design :- Existing Date/Time classes’ methods aren’t convenient to use in day-to-day programmer’s coding or development
  • Time-zone settings :- Developers or Programmer’s life becomes difficult while dealing with time zone settings in programs

Let’s move forward and discuss about java.time.Instant introduced in Java 1.8 version

1. ZonedDateTime v/s OffsetDateTime v/s Instant v/s LocalDateTime:

Before moving forward to detail out about Instant, let’s understand what are the difference between LocalDateTime & Instant & OffsetDateTime & ZonedDateTime

  • LocalDateTime provides date/time without Offset/Zone information in the below format,
    • yyyy-MM-ddTHH:mm:ss.nnn
    • For example, 2022-06-29T17:31:25.387081200
  • Instant provides/captures instantaneous moment or current date/time in UTC/GMT in the below format,
    • yyyy-MM-ddTHH:mm:ss.nnnZ
    • Where Z indicates zero or +00:00 or GMT/UTC time
    • For example, 2022-06-29T12:01:25.369081700Z
    • Note:- Instant date/time are time-zone unaware and it always returns current date/time at UTC/GMT
  • OffsetDateTime provides date/time with Offset but no Zone information in the below format,
    • yyyy-MM-ddTHH:mm:ss.nnn+HH:mm
    • So, OffsetDateTime is LocalDateTime plus Offset from GMT/UTC information
    • For example 2022-06-29T17:31:25.369081700+05:30
  • ZonedDateTime provides date/time with Offset from GMT/UTC & ZoneId information in the below format,
    • yyyy-MM-ddTHH:mm:ss.nnn+HH:mm[region/city]
    • So, ZonedDateTime is OffsetDateTime plus ZoneId information in Square-brackets,
    • For example 2022-06-29T17:31:25.368081700+05:30[Asia/Calcutta]
  • In the below illustration, we are printing ZonedDateTime, OffsetDateTime, Instant & LocalDateTime twice
    • First in the system default zone (i.e., Asia/Calcutta)
    • Second, after providing ZoneId or Clock (Asia/Dubai) as argument to overloaded now() method
  • ZonedDateTime, OffsetDateTime, Instant & LocalDateTime prints current date/time in their specific Zone except Instant
    1. LocalDateTime provides date/time to nano-second precision
    2. Instant provides date/time to nano-second precision in GMT/UTC
    3. OffsetDateTime provides date/time to nano-second precision and Offset from GMT/UTC information
    4. ZonedDateTime provides date/time to nano-second precision and Offset from GMT/UTC & ZoneId information
  • Note: Time-difference from Greenwich Mean Time (GMT) or Universal Time Coordinated (UTC) is known as Offset

InstantVsOffsetVsZonedVsLocalDateTime.java

package in.bench.resources.instant;

import java.time.Clock;
import java.time.Instant;
import java.time.LocalDateTime;
import java.time.OffsetDateTime;
import java.time.ZoneId;
import java.time.ZonedDateTime;

public class InstantVsOffsetVsZonedVsLocalDateTime {

	public static void main(String[] args) {

		// 1. ZonedDateTime, OffsetDateTime, Instant and LocalDateTime in system default zone
		System.out.println("1. ZonedDateTime, OffsetDateTime, Instant and LocalDateTime "
				+ "in system default zone - [" + ZoneId.systemDefault() + "]");


		// 1.1 ZonedDateTime - current date/time in default zone
		ZonedDateTime zonedDateTime = ZonedDateTime.now();
		System.out.println("\n1.1 ZonedDateTime :- \t" + zonedDateTime);


		// 1.2 OffsetDateTime - current date/time in default zone
		OffsetDateTime offsetDateTime = OffsetDateTime.now();
		System.out.println("1.2 OffsetDateTime :- \t" + offsetDateTime);


		// 1.3 Instant - current date/time in GMT/UTC
		Instant instant = Instant.now();
		System.out.println("1.3 Instant :- \t\t" + instant);


		// 1.4 ZonedDateTime - current date/time in default zone
		LocalDateTime localDateTime = LocalDateTime.now();
		System.out.println("1.4 LocalDateTime :- \t" + localDateTime);



		// 2. ZonedDateTime, OffsetDateTime, Instant and LocalDateTime in Asia/Dubai Zone 
		ZoneId zoneId = ZoneId.of("Asia/Dubai");
		System.out.println("\n\n2. ZonedDateTime, OffsetDateTime, Instant and LocalDateTime "
				+ "in [Asia/Dubai] Zone");


		// 2.1 current date/time in specific/passed zone
		ZonedDateTime zonedDateTime2 = ZonedDateTime.now(zoneId);
		System.out.println("\n2.1 ZonedDateTime :- \t" + zonedDateTime2);


		// 2.2 current date/time in specific/passed zone
		OffsetDateTime offsetDateTime2 = OffsetDateTime.now(zoneId);
		System.out.println("2.2 OffsetDateTime :- \t" + offsetDateTime2);


		// 2.3 Instant - current date/time in GMT/UTC
		Clock clock = Clock.systemDefaultZone();
		Instant instant2 = Instant.now(clock);
		System.out.println("2.3 Instant :- \t\t" + instant2);


		// 2.4 ZonedDateTime - current date/time in default zone
		LocalDateTime localDateTime2 = LocalDateTime.now(zoneId);
		System.out.println("2.4 LocalDateTime :- \t" + localDateTime2);
	}
}

Output:

1. ZonedDateTime, OffsetDateTime, Instant and LocalDateTime in system default zone - [Asia/Calcutta]

1.1 ZonedDateTime :- 	2022-06-29T21:36:19.000938100+05:30[Asia/Calcutta]
1.2 OffsetDateTime :- 	2022-06-29T21:36:19.000938100+05:30
1.3 Instant :- 		2022-06-29T16:06:19.000938100Z
1.4 LocalDateTime :- 	2022-06-29T21:36:19.015938200


2. ZonedDateTime, OffsetDateTime, Instant and LocalDateTime in [Asia/Dubai] Zone

2.1 ZonedDateTime :- 	2022-06-29T20:06:19.016938100+04:00[Asia/Dubai]
2.2 OffsetDateTime :- 	2022-06-29T20:06:19.016938100+04:00
2.3 Instant :- 		2022-06-29T16:06:19.016938100Z
2.4 LocalDateTime :- 	2022-06-29T20:06:19.016938100

2. Instant :

  • There are 3 ways to get/form an Instant,
    1. First is to get current date/time or instantaneous moment at GMT/UTC using static factory methods, 
      A. Instant.now()
      B. Instant.now(Clock)
    2. Second is to form an Instant using static factory methods,
      A. Instant.ofEpochSecond(long epochSecond)
      B. Instant.ofEpochMilli(long epochMilli)
      C. Instant.ofEpochSecond(long epochSecond, long nanoAdjustment)
    3. Third and final is to parse date/time at GMT/UTC in String-form to Instant using static factory method parse() such as 2022-06-29T12:01:25.369081700Z
  • The fully qualified package/class name of Instant is java.time.Instant i.e.; Instant is present under java.time package
  • Class declaration for Instant is as follows,
package java.time;
 
public final class Instant
        implements Temporal, TemporalAdjuster, Comparable<Instant>, Serializable {
}

3. Instant methods or APIs :

Important Instant method details,

  • now() – get current date-time to nano-second precision from the GMT/UTC (instantaneous moment at UTC)
  • now(Clock) – get current date-time to nano-second precision from the GMT/UTC (instantaneous moment at UTC), Instant are time-zone unaware
  • ofEpochSecond(long epochSecond) – get Instant using seconds from the epoch of 1970-01-01T00:00:00Z
  • ofEpochMilli(long epochMilli) – get Instant using milliseconds from the epoch of 1970-01-01T00:00:00Z
  • ofEpochSecond(long epochSecond, long nanoAdjustment) – get Instant using seconds from the epoch of 1970-01-01T00:00:00Z and nanosecond fraction of second
  • parse() – get an instance of Instant from a text string in either yyyy-MM-ddTHH:mm:ss.nnnZ or yyyy-MM-ddTHH:mm:ssZ formats
  • atOffset(ZoneOffset offset) – combines invoking Instant with an offset to create an OffsetDateTime
  • atZone(ZoneId zone) – combines invoking Instant with a time-zone to create a ZonedDateTime
  • getEpochSecond() – get number of seconds from the Java epoch of 1970-01-01T00:00:00Z
  • toEpochMilli() – converts Instant to the number of milliseconds from the epoch of 1970-01-01T00:00:00Z
  • getNano() – get number of nanoseconds, later along the time-line, from the start of the second
  • plusSeconds(long secondsToAdd) – Returns a copy of this Instant with the specified duration in seconds added
  • plusMillis(long millisToAdd) – Returns a copy of this Instant with the specified duration in milliseconds added
  • plusNanos(long nanosToAdd) – Returns a copy of this Instant with the specified duration in nanoseconds added
  • minusSeconds(long secondsToSubtract) – Returns a copy of this Instant with the specified duration in seconds subtracted
  • minusMillis(long millisToSubtract) – Returns a copy of this Instant with the specified duration in milliseconds subtracted
  • minusNanos(long nanosToSubtract) – Returns a copy of this Instant with the specified duration in nanoseconds subtracted
  • isAfter(Instant otherInstant) – checks if this Instant is after the specified Instant
  • isBefore(Instant otherInstant) – checks if this Instant is before the specified Instant

4. Instant examples :

  1. Get current Instant (date/time) in UTC/GMT
    • Instant.now() – get current date/time or instantaneous moment in UTC/GMT
    • Instant.now(Clock) – get current date/time or instantaneous moment in UTC/GMT, Instant are time-zone unaware
  2. Form an instance of Instant from the seconds or milliseconds passed
    • Instant.ofEpochSecond(long) – Obtains an instance of Instant using seconds from the epoch of 1970-01-01T00:00:00Z
    • Instant.ofEpochMilli(long) – Obtains an instance of Instant using milliseconds from the epoch of 1970-01-01T00:00:00Z
    • Instant.ofEpochSecond(long, long) – Obtains an instance of Instant using seconds from the epoch of 1970-01-01T00:00:00Z and nanosecond fraction of second
  3. Instant.parse() – parse Instant from a text string such as 2007-12-03T10:15:30.00Z
  4. Convert Instant to ZonedDateTime or OffsetDateTime
    • atOffset(ZoneOffset) – combines invoking Instant with an offset to create an OffsetDateTime
    • atZone(ZoneId) – combines invoking Instant with a time-zone to create a ZonedDateTime
  5. Get Instant in seconds or milliseconds or nanoseconds
    • getEpochSecond() – get invoking Instant into number of seconds from the Java epoch of 1970-01-01T00:00:00Z
    • toEpochMilli() – convert invoking Instant to the number of milliseconds from the epoch of 1970-01-01T00:00:00Z
    • getNano() – get invoking Instant into number of nanoseconds, later along the time-line, from the start of the second
  6. Adding nanoseconds, milliseconds and seconds to Instant using plusNanos(), plusMillis() and plusSeconds() methods respectively
  7. Subtracting nanoseconds, milliseconds and seconds to Instant using minusNanos(), minusMillis() and minusSeconds() methods respectively
  8. Check before and after Instant using below methods,
    • isBefore(Instant) – checks if invoking Instant is before the specified Instant
    • isAfter(Instant) – Checks if invoking Instant is after the specified Instant

4.1 Instant.now() method – get current Instant (date/time) in UTC/GMT:

InstantExampleUsingNowMethod.java

package in.bench.resources.instant;

import java.time.Clock;
import java.time.Instant;
import java.time.ZoneId;

public class InstantExampleUsingNowMethod {

	public static void main(String[] args) {

		// 1. get an instantaneous moment at GMT/UTC
		Instant instant = Instant.now();
		System.out.println("1. Current date/time at UTC/GMT is = " + instant);


		// 2. get an instantaneous moment at GMT/UTC passing Clock
		Clock clock = Clock.system(ZoneId.of("Asia/Dubai"));
		Instant instant2 = Instant.now(clock);
		System.out.println("\n2. Current date/time at UTC/GMT is = " + instant2);
	}
}

Output:

1. Current date/time at UTC/GMT is = 2022-06-29T16:06:42.076995800Z

2. Current date/time at UTC/GMT is = 2022-06-29T16:06:42.111670800Z

4.2 Get an Instant from the seconds or milliseconds:

  • Instant.ofEpochSecond(long) – Obtains an instance of Instant using seconds from the epoch of 1970-01-01T00:00:00Z
  • Instant.ofEpochMilli(long) – Obtains an instance of Instant using milliseconds from the epoch of 1970-01-01T00:00:00Z
  • Instant.ofEpochSecond(long, long) – Obtains an instance of Instant using seconds from the epoch of 1970-01-01T00:00:00Z and nanosecond fraction of second
  • Read Java 8 – How to get Seconds and Nanoseconds from an Instant ? for more details and examples

GetInstantFromSecondAndMilliAndNano.java

package in.bench.resources.instant;

import java.time.Instant;

public class GetInstantFromSecondAndMilliAndNano {

	public static void main(String[] args) {

		// 1. get an Instant from Milliseconds
		Instant instant1 = Instant.ofEpochMilli(Long.valueOf("1656513078830"));
		System.out.println("1. Instant.ofEpochMilli(Long.valueOf(\"1656513078830\")) :- " 
				+ instant1);


		// 2. get an Instant from Seconds
		Instant instant2 = Instant.ofEpochSecond(1656513061);
		System.out.println("\n2. Instant.ofEpochSecond(1656513061) :- "
				+ instant2);


		// 3. get an Instant from Seconds and Nanoseconds
		Instant instant3 = Instant.ofEpochSecond(1656513061, 125);
		System.out.println("\n3. Instant.ofEpochSecond(1656513061, 125) :- " 
				+ instant3);
	}
}

Output:

1. Instant.ofEpochMilli(Long.valueOf("1656513078830")) :- 2022-06-29T14:31:18.830Z

2. Instant.ofEpochSecond(1656513061) :- 2022-06-29T14:31:01Z

3. Instant.ofEpochSecond(1656513061, 125) :- 2022-06-29T14:31:01.000000125Z

4.3 Instant.parse() method – get Date/time in String-form:

  • Sometimes, we need to parse date/time passed in String-form to an Instant, for that we can use Instant.parse() method which will return Instant in yyyy-MM-ddTHH:mm:ss.nnnZ format
  • While parsing Date/Time, value in String-form should be in either of the below formats only, otherwise java.time.format.DateTimeParseException will be thrown
    • yyyy-MM-ddTHH:mm:ss.nnnZ
    • yyyy-MM-ddTHH:mm:ssZ
  • Read Java 8 – How to parse Instant in String form ? for more details and examples

InstantExampleUsingParseMethod.java

package in.bench.resources.instant;

import java.time.Instant;

public class InstantExampleUsingParseMethod {

	public static void main(String[] args) {

		// 1. parse Instant value in String-form to an Instant
		Instant instant1 = Instant.parse("2022-06-29T12:33:45.191546200Z");
		System.out.println("1. Parsed Date/time (yyyy-MM-ddTHH:mm:ss.nnnZ) :- " 
				+ instant1);


		// 2. parse Instant value in String-form to an Instant
		Instant instant2 = Instant.parse("2022-06-29T12:33:45Z");
		System.out.println("\n2. Parsed Date/time (yyyy-MM-ddTHH:mm:ssZ) :- " 
				+ instant2);
	}
}

Output:

1. Parsed Date/time (yyyy-MM-ddTHH:mm:ss.nnnZ) :- 2022-06-29T12:33:45.191546200Z

2. Parsed Date/time (yyyy-MM-ddTHH:mm:ssZ) :- 2022-06-29T12:33:45Z

4.4 Convert Instant to ZonedDateTime or OffsetDateTime:

ConvertInstantToZonedAndOffsetDateTime.java

package in.bench.resources.instant;

import java.time.Instant;
import java.time.OffsetDateTime;
import java.time.ZoneId;
import java.time.ZoneOffset;
import java.time.ZonedDateTime;

public class ConvertInstantToZonedAndOffsetDateTime {

	public static void main(String[] args) {

		// 1. get current Instant at UTC
		Instant instant = Instant.now();
		System.out.println("1. Current Date/time at UTC is :- \n" 
				+ instant);


		// 2. convert Instant into OffsetDateTime
		ZoneOffset zoneOffset = ZoneOffset.of("-06:00");
		OffsetDateTime offsetDateTime = instant.atOffset(zoneOffset);
		System.out.println("\n2. Current Date/time at Offset \"-06:00\" is :- \n" 
				+ offsetDateTime);


		// 3. convert Instant into ZonedDateTime
		ZoneId zoneId = ZoneId.of("Australia/Sydney");
		ZonedDateTime zonedDateTime = instant.atZone(zoneId);
		System.out.println("\n3. Current Date/time at [Australia/Sydney] zone is :- \n" 
				+ zonedDateTime);
	}
}

Output:

1. Current Date/time at UTC is :- 
2022-06-29T16:08:22.958632300Z

2. Current Date/time at Offset "-06:00" is :- 
2022-06-29T10:08:22.958632300-06:00

3. Current Date/time at [Australia/Sydney] zone is :- 
2022-06-30T02:08:22.958632300+10:00[Australia/Sydney]

4.5 Get Instant in seconds or milliseconds or nanoseconds:

GetInstantInSecondAndMilliAndNano.java

package in.bench.resources.instant;

import java.time.Instant;

public class GetInstantInSecondAndMilliAndNano {

	public static void main(String[] args) {

		// get current Date/time or Instant at UTC
		Instant instant = Instant.now();


		// 1. get Nanoseconds from an Instant
		int nanos = instant.getNano();
		System.out.println("1. Instant in Nanoseconds :- " 
				+ nanos);


		// 2. get Milliseconds from an Instant
		long millis = instant.toEpochMilli();
		System.out.println("\n2. Instant in Milliseconds :- " 
				+ millis);


		// 2. get Seconds from an Instant
		long seconds = instant.getEpochSecond();
		System.out.println("\n3. Instant in Seconds :- " 
				+ seconds);
	}
}

Output:

1. Instant in Nanoseconds :- 815586800

2. Instant in Milliseconds :- 1656518931815

3. Instant in Seconds :- 1656518931

4.6 Adding Nano/Millisecond/Second to an Instant:

AddToInstant.java

package in.bench.resources.instant;

import java.time.Instant;

public class AddToInstant {

	public static void main(String[] args) {

		// get current Date/time or Instant at UTC
		Instant instant = Instant.now();
		System.out.println("Current Instant at UTC is :- " 
				+ instant);


		// 1. add 125 Nanoseconds with current Instant
		Instant instant1 = instant.plusNanos(125);
		System.out.println("\n1. After adding 125 nanos to an Instant is = " 
				+ instant1);


		// 2. add 999 Milliseconds with current Instant
		Instant instant2 = instant.plusMillis(999);
		System.out.println("2. After adding 999 millis to an Instant is = " 
				+ instant2);


		// 3. add 19 Seconds with current Instant
		Instant instant3 = instant.plusSeconds(19);
		System.out.print("3. After adding 19 seconds to an Instant is = " 
				+ instant3);
	}
}

Output:

Current Instant at UTC is :- 2022-08-23T08:06:07.739563Z

1. After adding 125 nanos to an Instant is = 2022-08-23T08:06:07.739563125Z
2. After adding 999 millis to an Instant is = 2022-08-23T08:06:08.738563Z
3. After adding 19 seconds to an Instant is = 2022-08-23T08:06:26.739563Z

4.7 Subtracting Nano/Millisecond/Second to an Instant:

SubtractFromInstant.java

package in.bench.resources.instant;

import java.time.Instant;

public class SubtractFromInstant {

	public static void main(String[] args) {

		// get current Date/time or Instant at UTC
		Instant instant = Instant.now();
		System.out.println("Current Instant at UTC is :- " 
				+ instant);


		// 1. subtract 125 Nanoseconds with current Instant
		Instant instant1 = instant.minusNanos(125);
		System.out.println("\n1. After subtracting 125 nanos to an Instant is = " 
				+ instant1);


		// 2. subtract 999 Milliseconds with current Instant
		Instant instant2 = instant.minusMillis(999);
		System.out.println("2. After subtracting 999 millis to an Instant is = " 
				+ instant2);


		// 3. subtract 19 Seconds with current Instant
		Instant instant3 = instant.minusSeconds(19);
		System.out.print("3. After subtracting 19 seconds to an Instant is = " 
				+ instant3);
	}
}

Output:

Current Instant at UTC is :- 2022-08-23T08:07:36.853582Z

1. After subtracting 125 nanos to an Instant is = 2022-08-23T08:07:36.853581875Z
2. After subtracting 999 millis to an Instant is = 2022-08-23T08:07:35.854582Z
3. After subtracting 19 seconds to an Instant is = 2022-08-23T08:07:17.853582Z

4.8 Check Before/After Instant :

Compare2Instant.java

package in.bench.resources.instant;

import java.time.Instant;

public class Compare2Instant {

	public static void main(String[] args) {

		// 1. get current Instant at UTC
		Instant todayInstant = Instant.now();
		System.out.println("1. Current Instant is :- " + todayInstant);


		// 2. parse tomorrow Instant 
		String tomorrowInstantInStr = "2022-06-30T15:10:23.933345200Z";
		Instant tomorrowInstant = Instant.parse(tomorrowInstantInStr);
		System.out.println("2. Parsed FUTURE Instant is :- " + tomorrowInstant);


		// 3. parse yesterday Instant 
		String yesterdayInstantInStr = "2022-06-28T15:10:23.933345200Z";
		Instant yesterdayInstant = Instant.parse(yesterdayInstantInStr);
		System.out.println("3. Parsed PAST Instant is :- " + yesterdayInstant);


		// 4. isBefore() - Instant comparison
		System.out.println("\n4. Instant comparison with isBefore() method :- \n");


		// 4.1 check whether current Instant isBefore another tomorrow Instant
		boolean isBefore = todayInstant.isBefore(tomorrowInstant);
		System.out.println("4.1 Whether current Instant (" + todayInstant 
				+ ") is Before \n\t another TOMORROW Instant (" + tomorrowInstant + ") :- " 
				+ isBefore);


		// 4.2 check whether current Instant isBefore another yesterday Instant
		boolean isBefore2 = todayInstant.isBefore(yesterdayInstant);
		System.out.println("4.2 Whether current Instant (" + todayInstant 
				+ ") is Before \n\t another YESTERDAY Instant (" + yesterdayInstant + ") :- " 
				+ isBefore2);


		// 5. isAfter() - Instant comparison
		System.out.println("\n5. Instant comparison with isAfter() methods :- \n");


		// 5.1 check whether current Instant isAfter another yesterday Instant
		boolean isAfter = todayInstant.isAfter(yesterdayInstant);
		System.out.println("5.1 Whether current Instant (" + todayInstant 
				+ ") is After \n\t another YESTERDAY Instant (" + yesterdayInstant + ") :- " 
				+ isAfter);


		// 5.2 check whether current Instant isAfter another tomorrow Instant
		boolean isAfter2 = todayInstant.isAfter(tomorrowInstant);
		System.out.println("5.2 Whether current Instant (" + todayInstant 
				+ ") is After \n\t another TOMORROW Instant (" + tomorrowInstant + ") :- " 
				+ isAfter2);
	}
}

Output:

1. Current Instant is :- 2022-06-29T16:15:30.088237400Z
2. Parsed FUTURE Instant is :- 2022-06-30T15:10:23.933345200Z
3. Parsed PAST Instant is :- 2022-06-28T15:10:23.933345200Z

4. Instant comparison with isBefore() method :- 

4.1 Whether current Instant (2022-06-29T16:15:30.088237400Z) is Before 
	 another TOMORROW Instant (2022-06-30T15:10:23.933345200Z) :- true
4.2 Whether current Instant (2022-06-29T16:15:30.088237400Z) is Before 
	 another YESTERDAY Instant (2022-06-28T15:10:23.933345200Z) :- false

5. Instant comparison with isAfter() methods :- 

5.1 Whether current Instant (2022-06-29T16:15:30.088237400Z) is After 
	 another YESTERDAY Instant (2022-06-28T15:10:23.933345200Z) :- true
5.2 Whether current Instant (2022-06-29T16:15:30.088237400Z) is After 
	 another TOMORROW Instant (2022-06-30T15:10:23.933345200Z) :- false

Q) How to get Zones with Offset Z or +00:00 or UTC/GMT ?

  • ZoneId.getAvailableZoneIds(); provides all Zones in the form of Set<String>
  • To get Zones under specific Offset like “Z” or +00:00 or UTC/GMT, we can get stream and process as shown in the below illustration
  • Read Java 8 – How to display Zones for particular Offset ? for more details and examples

DisplayAllZonesForOffsetZ.java

package in.bench.resources.instant;

import java.time.ZoneId;
import java.time.ZonedDateTime;
import java.util.Set;

public class DisplayAllZonesForOffsetZ {

	public static void main(String[] args) {

		// 1. get all zones
		Set<String> zones = ZoneId.getAvailableZoneIds();


		// 1.1 print to console
		System.out.println("Zones with Offset Z or +00:00 or UTC/GMT :- \n");


		// 2. extract zones with Offset Z (+00:00) and print to console
		zones // original source
		.stream() // get stream
		.map(zone -> ZonedDateTime.now(ZoneId.of(zone))) // convert to ZonedDateTime
		.filter(zdt -> zdt.getOffset().toString().equalsIgnoreCase("Z")) // Filter Offset with Z
		.sorted((zdt1, zdt2) -> zdt1.getZone().toString().compareTo(zdt2.getZone().toString())) // sorting
		.forEach(zdt -> System.out.println(zdt.getOffset() + "\t" + zdt.getZone())); // printing
	}
}

Output:

Zones with Offset Z or +00:00 or UTC/GMT :- 

Z	Africa/Abidjan
Z	Africa/Accra
Z	Africa/Bamako
Z	Africa/Banjul
Z	Africa/Bissau
Z	Africa/Conakry
Z	Africa/Dakar
Z	Africa/Freetown
Z	Africa/Lome
Z	Africa/Monrovia
Z	Africa/Nouakchott
Z	Africa/Ouagadougou
Z	Africa/Sao_Tome
Z	Africa/Timbuktu
Z	America/Danmarkshavn
Z	America/Scoresbysund
Z	Atlantic/Azores
Z	Atlantic/Reykjavik
Z	Atlantic/St_Helena
Z	Etc/GMT
Z	Etc/GMT+0
Z	Etc/GMT-0
Z	Etc/GMT0
Z	Etc/Greenwich
Z	Etc/UCT
Z	Etc/UTC
Z	Etc/Universal
Z	Etc/Zulu
Z	GMT
Z	GMT0
Z	Greenwich
Z	Iceland
Z	UCT
Z	UTC
Z	Universal
Z	Zulu

Related Articles:

References:

Happy Coding !!
Happy Learning !!

Java 8 - How to display Zones for particular Offset ?
Java 8 – OffsetDateTime with method details and examples

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