Java 9 – How to convert java.util.Date to LocalDate using ofInstant() method ?

August 25, 2022 SJ Java 8, Java 8 Date/Time 0

In this article, we will learn how to convert an Date to LocalDate using newly introduced method in Java 1.9 version

Date class in Java 1.8 version :

  • There are 2 new methods introduced in Java 1.8 version for Date class, those are
    1. from(Instant) – This static method obtains an instance of Date from an Instant object
    2. toInstant() – This method converts invoking Date object to an Instant
  • Note: Many legacy methods of Date class are deprecated

1. Convert Date to LocalDate in Java 1.9 version :

  • First, convert Date to an Instant using toInstant() method of Date class
  • In Java 1.9 version a new method LocalDate.ofInstant() introduced for conversion from an Instant to LocalDate,
    • LocalDate.ofInstant​(Instant, ZoneId) – gets an instance of LocalDate from an Instant and zone ID passed

ConvertJavaUtilDateToLocalDate.java

package in.bench.resources.java9.conversion;

import java.time.Instant;
import java.time.LocalDate;
import java.time.ZoneId;
import java.util.Date;

public class ConvertJavaUtilDateToLocalDate {

	public static void main(String[] args) {

		// 1. get current date/time using java.util.Date
		Date date = new Date();
		System.out.println("Current Date/time is :- \n" 
				+ date);


		// 2. get default time zone
		ZoneId zoneId = ZoneId.systemDefault();
		System.out.println("\nDefault time-zone is :- \n" 
				+ zoneId);


		// 3. First, convert Date to Instant
		Instant instant = date.toInstant();
		System.out.println("\nInstant is :- \n" 
				+ instant);


		// 4. Second, Instant -> LocalDate
		LocalDate localDate = LocalDate
				.ofInstant(instant, zoneId);
		System.out.print("\nLocalDate is :- \n" 
				+ localDate);
	}
}

Output:

Current Date/time is :- 
Wed Aug 24 16:17:45 IST 2022

Default time-zone is :- 
Asia/Calcutta

Instant is :- 
2022-08-24T10:47:45.621Z

LocalDate is :- 
2022-08-24

2. Convert LocalDate to Date :

  • LocalDate consist of only Date information whereas java.util.Date requires Date, Time and Zone information
    • java.util.Date = LocalDate + Time + Zone information
    • For LocalDate to java.util.Date conversion, Time-Zone and Time information is required
  • Date.from() method accepts Instant as input-argument
    1. Convert LocalDate to ZonedDateTime using atStartOfDay() method passing ZoneId as argument and then invoke toInstant() method which returns an Instant
    2. Now, pass above converted Instant to Date.from() method which will return java.util.Date
  • Converted java.util.Date will have,
    1. Date part same as that of LocalDate
    2. Adding System default Zone information
    3. Time part fields hour/minute/second values set to 00
  • In short, LocalDate -> ZonedDateTime -> Instant -> java.util.Date
  • Lets see an example for conversion of LocalDate to java.util.Date in the below illustration

ConvertLocalDateToJavaUtilDate.java

package in.bench.resources.java9.conversion;

import java.time.Instant;
import java.time.LocalDate;
import java.time.ZoneId;
import java.time.ZonedDateTime;
import java.util.Date;

public class ConvertLocalDateToJavaUtilDate {

	public static void main(String[] args) {

		// 1. get current System Date
		LocalDate localDate = LocalDate.now();
		System.out.println("Current System Date is :- \n" 
				+ localDate);


		// 2. get system default zone
		ZoneId zoneId = ZoneId.systemDefault();
		System.out.println("\nDefault System Zone is :- \n" 
				+ zoneId);


		// 3. First, convert LocalDate to ZonedDateTime
		ZonedDateTime zonedDateTime = localDate.atStartOfDay(zoneId);
		System.out.println("\nZonedDateTime is :- \n" 
				+ zonedDateTime);


		// 4. Second, convert ZonedDateTime to Instant
		Instant instant = zonedDateTime.toInstant();
		System.out.println("\nInstant is :- \n" 
				+ instant);


		// 5. LocalDate -> ZonedDateTime -> Date
		Date date = Date.from(zonedDateTime.toInstant());
		System.out.print("\nConversion of LocalDate to java.util.Date is :- \n"
				+ date);
	}
}

Output:

Current System Date is :- 
2022-08-24

Default System Zone is :- 
Asia/Calcutta

ZonedDateTime is :- 
2022-08-24T00:00+05:30[Asia/Calcutta]

Instant is :- 
2022-08-23T18:30:00Z

Conversion of LocalDate to java.util.Date is :- 
Wed Aug 24 00:00:00 IST 2022

Related Articles:

References:

Happy Coding !!
Happy Learning !!

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