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About Mary Zheng

Mary Zheng
Mary has graduated from Mechanical Engineering department at ShangHai JiaoTong University. She also holds a Master degree in Computer Science from Webster University. During her studies she has been involved with a large number of projects ranging from programming and software engineering. She works as a senior Software Engineer in the telecommunications sector where she acts as a leader and works with others to design, implement, and monitor the software solution.

Java 8 TemporalAdjusters Example

1. Introduction

Java 8 Date-Time API is a JSR-310 implementation. It has a new set of packages to provide a comprehensive date-time model.

Java 8 Temporal is an interface which defines read-write access to a temporal object, such as the date, time, offset or a combination of these. Java 8 provides many common implementation classes: LocalDate, LocalTime, LocalDateTime, ZonedDateTime, Instant, JapaneseDate, ThaiBuddhistDate, HijrahDate, MinguoDate, etc.

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Java 8 TemporalAdjusters is a class which contains predefined static implementations for many common useful methods to modify temporal objects.

Method NameDescription
firstDayOfMonthReturns the “first day of month” adjuster, which returns a new date set it to the first day of the current month.
lastDayOfMonthReturns the “last day of month” adjuster, which returns a new date set it to the last day of the current month.
firstDayOfNextMonthReturns the “first day of next month” adjuster, which returns a new date set it to the first day of the next month.
firstDayOfYearReturns the “first day of the year” adjuster, which returns a new date set it to the first day of the current year.
lastDayOfYearReturns the “last day of the year” adjuster, which returns a new date set it to the last day of the current year.
firstDayOfNextYearReturns the “first day of next year” adjuster, which returns a new date set it to the first day of the next year.
firstInMonthReturns the “first day-of-week within a month” adjuster, which returns a new date in the same month with the first matching day-of-week. Such as “first Wednesday in June”.
lastInMonthReturns the “last day-of-week within a month adjuster”, such as “last Thursday in November”
dayOfWeekInMonthReturns the “day-of-week in month” adjuster, which returns a new date in the same month with the ordinal day-of-week.
nextReturns the “next day-of-week” adjuster, which adjusts the date to the first occurrence of the specified day-of-week after the date being adjusted.
previousReturns the “previous day-of-week” adjuster, which adjusts the date to the first occurrence of the specified day-of-week before the date being adjusted.

In this example, I will demonstrate how to adjust the date in LocalDate, LocalDateTime, ZonedDateTime, JapaneseDateThaiBuddhistDate, HijrahDate, MinguoDate using TemporalAdjusters.

2. Technologies used

The example code in this article was built and run using:

  • Java 1.8.101
  • Maven 3.3.9
  • Eclipse Oxygen
  • JUnit 4.12

3. Maven Project

3.1 Dependency

Add JUnit to the pom.xml.

pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<groupId>zheng.jcg.demo</groupId>
	<artifactId>java8-demo</artifactId>
	<version>0.0.1-SNAPSHOT</version>

	<dependencies>
		<dependency>
			<groupId>junit</groupId>
			<artifactId>junit</artifactId>
			<version>4.12</version>
			<scope>test</scope>
		</dependency>
	</dependencies>
	<build>
		<plugins>
			<plugin>
				<artifactId>maven-compiler-plugin</artifactId>
				<version>3.3</version>
				<configuration>
					<source>1.8</source>
					<target>1.8</target>
				</configuration>
			</plugin>
		</plugins>
	</build>
</project>

4. Custom TemporalAdjuster

4.1 HolidayAdjuster

If you work on a system which needs to find holidays like Mother’s Day, Father’s Day, Labor Day, or Thanksgiving, you can do so with TemporalAdjusters.dayOfWeekInMonth in a few lines of codes. In this step, I will create a HolidayAdjuster class to find a holiday as a LocalDate.

HolidayAdjuster.java

package com.zheng.demo;

import java.time.DayOfWeek;
import java.time.LocalDate;
import java.time.Month;
import java.time.temporal.Temporal;
import java.time.temporal.TemporalAdjuster;
import java.time.temporal.TemporalAdjusters;

public class HolidayAdjuster implements TemporalAdjuster {

	private static final int FIRST_DAY = 1;

	public HolidayAdjuster(Month month, int ordinal, DayOfWeek dayOfWeek) {
		super();
		this.month = month;
		this.dayOfWeek = dayOfWeek;
		this.ordinal = ordinal;
	}

	private Month month;
	private DayOfWeek dayOfWeek;
	private int ordinal;

	@Override
	public Temporal adjustInto(Temporal temporalAdjusterInput) {
		LocalDate temporalAdjusterDate = LocalDate.from(temporalAdjusterInput);
		LocalDate holidayMonth = LocalDate.of(temporalAdjusterDate.getYear(), month, FIRST_DAY);
		return holidayMonth.with(TemporalAdjusters.dayOfWeekInMonth(ordinal, dayOfWeek));		
	}

}

4.2 HolidayAdjusterTest

In this step, I will create four unit test cases to output the date for Mother’s day, Father’s Day, Labor Day, and Thanksgiving. Please note that the Temporal must be a LocalDate type.

HolidayAdjusterTest.java

package com.zheng.demo;

import java.time.DateTimeException;
import java.time.DayOfWeek;
import java.time.LocalDate;
import java.time.LocalTime;
import java.time.Month;

import org.junit.Before;
import org.junit.Test;

public class HolidayAdjusterTest {

	private LocalDate localDate;

	@Before
	public void setup() {
		localDate = LocalDate.now();
		System.out.print("\nCurrent localDate : " + localDate + ". ");
	}

	@Test
	public void mothersDay_customerAdjuster() {
		HolidayAdjuster mothersDayAdjuster = new HolidayAdjuster(Month.MAY, 2, DayOfWeek.SUNDAY);
		LocalDate mothersDay = localDate.with(mothersDayAdjuster);
		System.out.println("Mother's Day : " + mothersDay);
	}

	@Test
	public void fathersDay_customerAdjuster() {
		HolidayAdjuster fathersDayAdjuster = new HolidayAdjuster(Month.JUNE, 3, DayOfWeek.SUNDAY);
		LocalDate fathersDay = localDate.with(fathersDayAdjuster);
		System.out.println("Father's Day : " + fathersDay);
	}

	@Test
	public void laborDay_customerAdjuster() {
		HolidayAdjuster laborDayAdjuster = new HolidayAdjuster(Month.SEPTEMBER, 1, DayOfWeek.MONDAY);
		LocalDate laborDay = localDate.with(laborDayAdjuster);
		System.out.println("Labor Day : " + laborDay);
	}

	@Test
	public void thanksGivingDate_customAdjuster() {
		HolidayAdjuster thanksgivingAdjuster = new HolidayAdjuster(Month.NOVEMBER, 4, DayOfWeek.THURSDAY);
		LocalDate thanksGivingDay = localDate.with(thanksgivingAdjuster);
		System.out.println("Thanksgiving Date: " + thanksGivingDay);
	}

	@Test(expected=DateTimeException.class)
	public void exception_wrongtype() {
		LocalTime test = LocalTime.now();
		System.out.println("Throw Exception if not LocalDate.");
		test.with(new HolidayAdjuster(Month.NOVEMBER, 4,
				DayOfWeek.THURSDAY));
	}

}

Execute HolidayAdjusterTest as Junit test and capture the output here.

Junit Output

Current localDate : 2018-11-28. Labor Day : 2018-09-03

Current localDate : 2018-11-28. Father's Day : 2018-06-17

Current localDate : 2018-11-28. Thanksgiving Date: 2018-11-22

Current localDate : 2018-11-28. Throw Exception if not LocalDate.

Current localDate : 2018-11-28. Mother's Day : 2018-05-13

4.3 PaydayAdjuster

Company A schedules to cut the paycheck at 10 AM twice a month, one is on the 15th day of every month, the other is on the last day of every month. If it is on a Saturday or Sunday, then it is set to Friday. In this step, I will create a PayDayAdjuster class to find the next payday as a LocalDateTime with the previous and lastDayOfMonth methods.

PaydayAdjuster.java

package com.zheng.demo;

import java.time.DayOfWeek;
import java.time.LocalDateTime;
import java.time.temporal.Temporal;
import java.time.temporal.TemporalAdjuster;
import java.time.temporal.TemporalAdjusters;

public class PaydayAdjuster implements TemporalAdjuster {

	private static final int TEN_OCLOCK = 10;
	private static final int MID_MONTH_DAY = 15;

	public PaydayAdjuster() {
		super();

	}

	@Override
	public Temporal adjustInto(Temporal temporalAdjusterInput) {
		LocalDateTime orgDate = LocalDateTime.from(temporalAdjusterInput);
		LocalDateTime date = LocalDateTime.of(orgDate.getYear(), orgDate.getMonth(), orgDate.getDayOfMonth(),
				TEN_OCLOCK, 0);

		int day;
		if (date.getDayOfMonth() < MID_MONTH_DAY) {
			day = MID_MONTH_DAY;
		} else {
			day = date.with(TemporalAdjusters.lastDayOfMonth()).getDayOfMonth();
		}
		date = date.withDayOfMonth(day);
		if (date.getDayOfWeek() == DayOfWeek.SATURDAY || date.getDayOfWeek() == DayOfWeek.SUNDAY) {
			date = date.with(TemporalAdjusters.previous(DayOfWeek.FRIDAY));
		}

		return temporalAdjusterInput.with(date);
	}

}

4.4 PaydayAdjusterTest

In this step, I will create unit test cases to output the next payday. Please note that Temporal must be a LocalDateTime type.

PaydayAdjusterTest.java

package com.zheng.demo;

import java.time.DateTimeException;
import java.time.DayOfWeek;
import java.time.LocalDate;
import java.time.LocalDateTime;
import java.time.Month;
import java.time.temporal.TemporalAdjusters;

import org.junit.Before;
import org.junit.Test;

public class PaydayAdjusterTest {

	private LocalDateTime localDate;

	@Before
	public void setup() {
		localDate = LocalDateTime.now();
		System.out.print("\nCurrent LocalDateTime : " + localDate + ". ");
	}

	@Test
	public void nextPayDay() {
		LocalDateTime payDate = localDate.with(new PaydayAdjuster());
		System.out.println("Next Pay Day : " + payDate);
	}

	@Test
	public void nextMonthPayDay() {
		LocalDateTime firstMonth = localDate.with(TemporalAdjusters.firstDayOfNextMonth());
		LocalDateTime payDate = firstMonth.with(new PaydayAdjuster());
		System.out.println("Next Month Pay Day : " + payDate);
	}

	@Test(expected = DateTimeException.class)
	public void exception_wrongtype() {
		LocalDate test = LocalDate.now();
		System.out.println("Throw Exception if not LocalDateTime.");
		test.with(new HolidayAdjuster(Month.NOVEMBER, 4, DayOfWeek.THURSDAY));
	}

}

Execute it as Junit test and capture the output.

PaydayAdjusterTest Output

Current LocalDateTime : 2018-11-28T08:55:55.887. Next Month Pay Day : 2018-12-14T10:00

Current LocalDateTime : 2018-11-28T08:55:55.950. Next Pay Day : 2018-11-30T10:00

Current LocalDateTime : 2018-11-28T08:55:55.950. Throw Exception if not LocalDateTime.

5. JUnit Tests

Java 8 TemporalAdjusters provides lots of out-of-box solutions for adjusting the date. In this step, I will create JUnit tests to demonstrate how to use these pre-defined static methods to modify temporal objects.

5.1 TemporalAdjusters_LocalDateTest

Java 8 LocalDate represents a date without a time zone or time. In this step, I will adjust the year, month, and day with the pre-defined methods: firstDayOfYear, firstDayOfMonth, etc.

TemporalAdjusters_LocalDateTest.java

package com.zheng.demo;

import static org.junit.Assert.assertEquals;

import java.time.DayOfWeek;
import java.time.LocalDate;
import java.time.temporal.ChronoField;
import java.time.temporal.ChronoUnit;
import java.time.temporal.TemporalAdjuster;
import java.time.temporal.TemporalAdjusters;

import org.junit.Before;
import org.junit.Test;

public class TemporalAdjusters_LocalDateTest {

	private LocalDate localDate;

	@Before
	public void setup() {
		localDate = LocalDate.now();
		System.out.println("\nCurrent localDate : " + localDate);
	}

	@Test
	public void adjuster_firstDayOfMonth() {
		LocalDate updatedDate = localDate.with(TemporalAdjusters.firstDayOfMonth());
		System.out.println("firstDayOfMonth : " + updatedDate);
	}

	@Test
	public void adjuster_firstDayOfYear() {
		LocalDate updatedDate = localDate.with(TemporalAdjusters.firstDayOfYear());
		System.out.println("firstDayOfYear : " + updatedDate);
	}

	@Test
	public void adjuster_lastDayOfYear() {
		LocalDate updatedDate = localDate.with(TemporalAdjusters.lastDayOfYear());
		System.out.println("lastDayOfYear : " + updatedDate);
	}

	@Test
	public void adjuster_firstDayOfNextYear() {
		LocalDate updatedDate = localDate.with(TemporalAdjusters.firstDayOfNextYear());
		System.out.println("firstDayOfNextYear : " + updatedDate);
	}

	@Test
	public void adjuster_firstDayOfNextMonth() {
		LocalDate updatedDate = localDate.with(TemporalAdjusters.firstDayOfNextMonth());
		System.out.println("firstDayOfNextMonth : " + updatedDate);
	}

	@Test
	public void adjuster_lastDayOfMonth() {
		LocalDate updatedDate = localDate.with(TemporalAdjusters.lastDayOfMonth());
		System.out.println("lastDayOfMonth : " + updatedDate);

	}

	@Test
	public void adjuster_nextMonday() {
		LocalDate updatedDate = localDate.with(TemporalAdjusters.next(DayOfWeek.MONDAY));
		System.out.println("nextMonday : " + updatedDate);
	}

	@Test
	public void adjuster_nextSunday() {
		LocalDate localDate = LocalDate.of(2018, 11, 10);
		LocalDate nextSunday = localDate.with(TemporalAdjusters.next(DayOfWeek.SUNDAY));

		assertEquals("2018-11-11", nextSunday.toString());
	}

	@Test
	public void adjuster_firstInMonth() {
		LocalDate updatedDate = localDate.with(TemporalAdjusters.firstInMonth(DayOfWeek.MONDAY));
		System.out.println("firstInMonth_Monday: " + updatedDate);
	}

	@Test
	public void adjuster_previousWednesday() {
		LocalDate updatedDate = localDate.with(TemporalAdjusters.previous(DayOfWeek.WEDNESDAY));
		System.out.println("previousWednesday : " + updatedDate);
	}

	@Test
	public void christmasDay_customAdjuster() {
		TemporalAdjuster xmas = temporal -> temporal.with(ChronoField.MONTH_OF_YEAR, 12).with(ChronoField.DAY_OF_MONTH,
				25);

		LocalDate xmasDate = localDate.with(xmas);
		System.out.println("Christmas : " + xmasDate + ", it's on " + xmasDate.getDayOfWeek());
	}

	@Test
	public void tenDaysLater() {
		TemporalAdjuster tenDaysFromNow = temporal -> temporal.plus(10, ChronoUnit.DAYS);

		LocalDate localTimeUpdate = localDate.with(tenDaysFromNow);
		System.out.println("Ten Days later : " + localTimeUpdate);
	}

}

5.2 TemporalAdjusters_LocalDateTimeTest

Java 8 LocalDateTime represents a date without a time zone. I will repeat the same adjustment for the LocalDateTime type.

TemporalAdjusters_LocalDateTimeTest.java

package com.zheng.demo;

import java.time.DayOfWeek;
import java.time.Duration;
import java.time.LocalDateTime;
import java.time.temporal.ChronoField;
import java.time.temporal.ChronoUnit;
import java.time.temporal.TemporalAdjuster;
import java.time.temporal.TemporalAdjusters;

import org.junit.Before;
import org.junit.Test;

public class TemporalAdjusters_LocalDateTimeTest {

	private LocalDateTime localDateTime;

	@Before
	public void setup() {
		localDateTime = LocalDateTime.now();
		System.out.println("\nCurrent LocalDateTime : " + localDateTime);
	}

	@Test
	public void adjuster_firstDayOfMonth() {
		LocalDateTime updatedDate = localDateTime.with(TemporalAdjusters.firstDayOfMonth());
		System.out.println("firstDayOfMonth : " + updatedDate);
	}

	@Test
	public void adjuster_firstDayOfNextMonth() {
		LocalDateTime updatedDate = localDateTime.with(TemporalAdjusters.firstDayOfNextMonth());
		System.out.println("firstDayOfNextMonth : " + updatedDate);
	}

	@Test
	public void adjuster_lastDayOfMonth() {
		LocalDateTime updatedDate = localDateTime.with(TemporalAdjusters.lastDayOfMonth());
		System.out.println("lastDayOfMonth : " + updatedDate);

	}

	@Test
	public void adjuster_nextMonday() {
		LocalDateTime updatedDate = localDateTime.with(TemporalAdjusters.next(DayOfWeek.MONDAY));
		System.out.println("Next Monday : " + updatedDate);
	}

	@Test
	public void adjuster_previousWednesday() {
		LocalDateTime updatedDate = localDateTime.with(TemporalAdjusters.previous(DayOfWeek.WEDNESDAY));
		System.out.println("Previous Wednesday : " + updatedDate);
	}

	@Test
	public void christmasDay() {
		TemporalAdjuster xmas = temporal -> temporal.with(ChronoField.MONTH_OF_YEAR, 12).with(ChronoField.DAY_OF_MONTH,
				25);

		LocalDateTime xmasDate = localDateTime.with(xmas);
		System.out.println("Christmas : " + xmasDate + ", it's on " + xmasDate.getDayOfWeek());
	}

	@Test
	public void tenDaysThreeHourLater() {
		TemporalAdjuster tenDaysThreeHoursFromNow = temporal -> temporal.plus(10, ChronoUnit.DAYS)
				.plus(Duration.ofHours(3));

		LocalDateTime localTimeUpdate = localDateTime.with(tenDaysThreeHoursFromNow);
		System.out.println("Ten Days later : " + localTimeUpdate);
	}

}

5.3 TemporalAdjusters_ZonedDateTimeTest

Java 8 ZonedDateTime represents a date with a time zone. In this step, I will repeat the same adjustment for the ZonedDateTime class.

TemporalAdjusters_ZonedDateTimeTest.java

package com.zheng.demo;

import java.time.DayOfWeek;
import java.time.ZonedDateTime;
import java.time.temporal.ChronoField;
import java.time.temporal.ChronoUnit;
import java.time.temporal.TemporalAdjuster;
import java.time.temporal.TemporalAdjusters;

import org.junit.Before;
import org.junit.Test;

public class TemporalAdjusters_ZonedDateTimeTest {

	private ZonedDateTime zonedDateTime;

	@Before
	public void setup() {
		zonedDateTime = ZonedDateTime.now();
		System.out.println("\nCurrent ZonedDateTime : " + zonedDateTime);
	}

	@Test
	public void adjuster_firstDayOfMonth() {
		ZonedDateTime updatedDate = zonedDateTime.with(TemporalAdjusters.firstDayOfMonth());
		System.out.println("firstDayOfMonth : " + updatedDate);
	}

	@Test
	public void adjuster_firstDayOfYear() {
		ZonedDateTime updatedDate = zonedDateTime.with(TemporalAdjusters.firstDayOfYear());
		System.out.println("firstDayOfYear : " + updatedDate);
	}

	@Test
	public void adjuster_lastDayOfYear() {
		ZonedDateTime updatedDate = zonedDateTime.with(TemporalAdjusters.lastDayOfYear());
		System.out.println("lastDayOfYear : " + updatedDate);
	}

	@Test
	public void adjuster_firstDayOfNextYear() {
		ZonedDateTime updatedDate = zonedDateTime.with(TemporalAdjusters.firstDayOfNextYear());
		System.out.println("firstDayOfNextYear : " + updatedDate);
	}

	@Test
	public void adjuster_firstDayOfNextMonth() {
		ZonedDateTime updatedDate = zonedDateTime.with(TemporalAdjusters.firstDayOfNextMonth());
		System.out.println("firstDayOfNextMonth : " + updatedDate);
	}

	@Test
	public void adjuster_lastDayOfMonth() {
		ZonedDateTime updatedDate = zonedDateTime.with(TemporalAdjusters.lastDayOfMonth());
		System.out.println("lastDayOfMonth : " + updatedDate);

	}

	@Test
	public void adjuster_nextMonday() {
		ZonedDateTime updatedDate = zonedDateTime.with(TemporalAdjusters.next(DayOfWeek.MONDAY));
		System.out.println("nextMonday : " + updatedDate);
	}

	@Test
	public void adjuster_firstInMonth() {
		ZonedDateTime updatedDate = zonedDateTime.with(TemporalAdjusters.firstInMonth(DayOfWeek.MONDAY));
		System.out.println("firstInMonth_Monday: " + updatedDate);
	}

	@Test
	public void adjuster_previousWednesday() {
		ZonedDateTime updatedDate = zonedDateTime.with(TemporalAdjusters.previous(DayOfWeek.WEDNESDAY));
		System.out.println("previousWednesday : " + updatedDate);
	}

	@Test
	public void christmasDay() {
		TemporalAdjuster xmas = temporal -> temporal.with(ChronoField.MONTH_OF_YEAR, 12).with(ChronoField.DAY_OF_MONTH,
				25);

		ZonedDateTime xmasDate = zonedDateTime.with(xmas);
		System.out.println("Christmas : " + xmasDate + ", it's on " + xmasDate.getDayOfWeek());
	}

	@Test
	public void tenDaysLater() {
		TemporalAdjuster tenDaysFromNow = temporal -> temporal.plus(10, ChronoUnit.DAYS);

		ZonedDateTime localTimeUpdate = zonedDateTime.with(tenDaysFromNow);
		System.out.println("Ten Days later : " + localTimeUpdate);
	}
	
}

5.4 TemporalAdjusters_MinguoDateTest

Java 8 MinGuoDate represents a date in the Minguo calendar system. It is primarily used in the Republic of China, often known as Taiwan. I will repeat the same adjustment for the MinGuoDate class.

TemporalAdjusters_MinguoDateTest.java

package com.zheng.demo;

import java.time.DayOfWeek;
import java.time.chrono.MinguoDate;
import java.time.temporal.ChronoUnit;
import java.time.temporal.TemporalAdjuster;
import java.time.temporal.TemporalAdjusters;

import org.junit.Before;
import org.junit.Test;

public class TemporalAdjusters_MinguoDateTest {

	private MinguoDate minguoDate;

	@Before
	public void setup() {
		minguoDate = MinguoDate.now();
		System.out.println("\nCurrent MinguoDate : " + minguoDate);
	}

	@Test
	public void adjuster_firstDayOfMonth() {
		MinguoDate updatedDate = minguoDate.with(TemporalAdjusters.firstDayOfMonth());
		System.out.println("firstDayOfMonth : " + updatedDate);
	}

	@Test
	public void adjuster_firstDayOfYear() {
		MinguoDate updatedDate = minguoDate.with(TemporalAdjusters.firstDayOfYear());
		System.out.println("firstDayOfYear : " + updatedDate);
	}

	@Test
	public void adjuster_lastDayOfYear() {
		MinguoDate updatedDate = minguoDate.with(TemporalAdjusters.lastDayOfYear());
		System.out.println("lastDayOfYear : " + updatedDate);
	}

	@Test
	public void adjuster_firstDayOfNextYear() {
		MinguoDate updatedDate = minguoDate.with(TemporalAdjusters.firstDayOfNextYear());
		System.out.println("firstDayOfNextYear : " + updatedDate);
	}

	@Test
	public void adjuster_firstDayOfNextMonth() {
		MinguoDate updatedDate = minguoDate.with(TemporalAdjusters.firstDayOfNextMonth());
		System.out.println("firstDayOfNextMonth : " + updatedDate);
	}

	@Test
	public void adjuster_lastDayOfMonth() {
		MinguoDate updatedDate = minguoDate.with(TemporalAdjusters.lastDayOfMonth());
		System.out.println("lastDayOfMonth : " + updatedDate);

	}

	@Test
	public void adjuster_nextMonday() {
		MinguoDate updatedDate = minguoDate.with(TemporalAdjusters.next(DayOfWeek.MONDAY));
		System.out.println("nextMonday : " + updatedDate);
	}


	@Test
	public void adjuster_firstInMonth() {
		MinguoDate updatedDate = minguoDate.with(TemporalAdjusters.firstInMonth(DayOfWeek.MONDAY));
		System.out.println("firstInMonth_Monday: " + updatedDate);
	}

	@Test
	public void adjuster_previousWednesday() {
		MinguoDate updatedDate = minguoDate.with(TemporalAdjusters.previous(DayOfWeek.WEDNESDAY));
		System.out.println("previousWednesday : " + updatedDate);
	}

	@Test
	public void tenDaysLater() {
		TemporalAdjuster tenDaysFromNow = temporal -> temporal.plus(10, ChronoUnit.DAYS);

		MinguoDate localTimeUpdate = minguoDate.with(tenDaysFromNow);
		System.out.println("Ten Days later : " + localTimeUpdate);
	}

}

5.5 TemporalAdjusters_JapaneseDateTest

Java 8 JapaneseDate represents a date in the Japanese Imperial calendar system. I will repeat the same adjustment for the JapaneseDate class.

TemporalAdjusters_JapaneseDateTest.java

package com.zheng.demo;

import java.time.DayOfWeek;
import java.time.chrono.JapaneseDate;
import java.time.temporal.ChronoUnit;
import java.time.temporal.TemporalAdjuster;
import java.time.temporal.TemporalAdjusters;

import org.junit.Before;
import org.junit.Test;

public class TemporalAdjusters_JapaneseDateTest {

	private JapaneseDate japaneseDate;

	@Before
	public void setup() {
		japaneseDate = JapaneseDate.now();
		System.out.println("\nCurrent JapaneseDate : " + japaneseDate);
	}

	@Test
	public void adjuster_firstDayOfMonth() {
		JapaneseDate updatedDate = japaneseDate.with(TemporalAdjusters.firstDayOfMonth());
		System.out.println("firstDayOfMonth : " + updatedDate);
	}

	@Test
	public void adjuster_firstDayOfYear() {
		JapaneseDate updatedDate = japaneseDate.with(TemporalAdjusters.firstDayOfYear());
		System.out.println("firstDayOfYear : " + updatedDate);
	}

	@Test
	public void adjuster_lastDayOfYear() {
		JapaneseDate updatedDate = japaneseDate.with(TemporalAdjusters.lastDayOfYear());
		System.out.println("lastDayOfYear : " + updatedDate);
	}

	@Test
	public void adjuster_firstDayOfNextYear() {
		JapaneseDate updatedDate = japaneseDate.with(TemporalAdjusters.firstDayOfNextYear());
		System.out.println("firstDayOfNextYear : " + updatedDate);
	}

	@Test
	public void adjuster_firstDayOfNextMonth() {
		JapaneseDate updatedDate = japaneseDate.with(TemporalAdjusters.firstDayOfNextMonth());
		System.out.println("firstDayOfNextMonth : " + updatedDate);
	}

	@Test
	public void adjuster_lastDayOfMonth() {
		JapaneseDate updatedDate = japaneseDate.with(TemporalAdjusters.lastDayOfMonth());
		System.out.println("lastDayOfMonth : " + updatedDate);

	}

	@Test
	public void adjuster_nextMonday() {
		JapaneseDate updatedDate = japaneseDate.with(TemporalAdjusters.next(DayOfWeek.MONDAY));
		System.out.println("nextMonday : " + updatedDate);
	}


	@Test
	public void adjuster_firstInMonth() {
		JapaneseDate updatedDate = japaneseDate.with(TemporalAdjusters.firstInMonth(DayOfWeek.MONDAY));
		System.out.println("firstInMonth_Monday: " + updatedDate);
	}

	@Test
	public void adjuster_previousWednesday() {
		JapaneseDate updatedDate = japaneseDate.with(TemporalAdjusters.previous(DayOfWeek.WEDNESDAY));
		System.out.println("previousWednesday : " + updatedDate);
	}

	@Test
	public void tenDaysLater() {
		TemporalAdjuster tenDaysFromNow = temporal -> temporal.plus(10, ChronoUnit.DAYS);

		JapaneseDate localTimeUpdate = japaneseDate.with(tenDaysFromNow);
		System.out.println("Ten Days later : " + localTimeUpdate);
	}

}

6. Summary

In this example, we reviewed Java 8 Date time API and demonstrated how to use the pre-defined static methods in TemporalAdjusters to adjust the date at LocalDate, LocalDateTime, JapaneseDate, MinguoDate, and ZonedDateTime.

7. Download the Source Code

This example consists of a Maven project which adjusts LocalDate, LocatDateTime, JapaneseDate, MinguoDate, and ZonedDateTime using Java 8 TemporalAdjusters.

Download
You can download the full source code of this example here: Java 8 TemporalAdjusters Example
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