Table of Contents

Java LocalDateTime Class

新的日期時間 API 跟以往複雜的日期時間 API 有著很大的不同，像是將區域分離，讓物件功能更加專職，簡化了許多日期時間的操作方法，提供增加、減少、比較日期時間、或兩個日期時間差值的方法， LocalDateTime Class 介紹常見的 plus 、 minus 、 isBefore 、 isAfter 、 until 等方法，本篇增加了範例，並透過單元測試來驗證產出結果。

檔案目錄

./
   +- src
       +- test
       |   +- org
       |       +- ruoxue
       |           +- java_147
       |               +- datetime
       |                   +- localdatetime
       |                       +- LocalDateTimeClassTest.java

單元測試

LocalDateTime Class Java 提供日期時間加減、比較前後等操作 LocalDateTime 。

plus

LocalDateTime Class Java 建立一個 LocalDateTime ，提供指定日期時間加法運算。

	@Test
	public void plus() {
		LocalDateTime localDateTime = LocalDateTime.of(2023, 8, 3, 1, 2, 3);
		LocalDateTime result = localDateTime.plusYears(1);
		int year = result.getYear();
		System.out.println(year);
		assertEquals(2024, year);

		result = localDateTime.plusMonths(1);
		int month = result.getMonthValue();
		System.out.println(month);
		assertEquals(9, month);

		result = localDateTime.plusDays(1);
		int dayOfMonth = result.getDayOfMonth();
		System.out.println(dayOfMonth);
		assertEquals(4, dayOfMonth);

		result = localDateTime.plusHours(1);
		int hour = result.getHour();
		System.out.println(hour);
		assertEquals(2, hour);

		result = localDateTime.plusMinutes(1);
		int minute = result.getMinute();
		System.out.println(minute);
		assertEquals(3, minute);

		result = localDateTime.plusSeconds(1);
		int second = result.getSecond();
		System.out.println(second);
		assertEquals(4, second);
	}

plusTemporalAmount

LocalDateTime Class Java 建立一個 LocalDateTime ，使用 Period 、 Duration 提供指定日期時間加法運算。

	@Test
	public void plusTemporalAmount() {
		LocalDateTime localDateTime = LocalDateTime.of(2023, 8, 3, 1, 2, 3);
		LocalDateTime result = localDateTime.plus(Period.ofYears(1));
		int year = result.getYear();
		System.out.println(year);
		assertEquals(2024, year);

		result = localDateTime.plus(Period.ofMonths(1));
		int month = result.getMonthValue();
		System.out.println(month);
		assertEquals(9, month);

		result = localDateTime.plus(Period.ofDays(1));
		int dayOfMonth = result.getDayOfMonth();
		System.out.println(dayOfMonth);
		assertEquals(4, dayOfMonth);

		result = localDateTime.plus(Duration.ofHours(1));
		int hour = result.getHour();
		System.out.println(hour);
		assertEquals(2, hour);

		result = localDateTime.plus(Duration.ofMinutes(1));
		int minute = result.getMinute();
		System.out.println(minute);
		assertEquals(3, minute);

		result = localDateTime.plus(Duration.ofSeconds(1));
		int second = result.getSecond();
		System.out.println(second);
		assertEquals(4, second);
	}

minus

LocalDateTime Class Java 建立一個 LocalDateTime ，提供指定日期時間減法運算。

	@Test
	public void minus() {
		LocalDateTime localDateTime = LocalDateTime.of(2023, 8, 3, 1, 2, 3);
		LocalDateTime result = localDateTime.minusYears(1);
		int year = result.getYear();
		System.out.println(year);
		assertEquals(2022, year);

		result = localDateTime.minusMonths(1);
		int month = result.getMonthValue();
		System.out.println(month);
		assertEquals(7, month);

		result = localDateTime.minusDays(1);
		int dayOfMonth = result.getDayOfMonth();
		System.out.println(dayOfMonth);
		assertEquals(2, dayOfMonth);

		result = localDateTime.minusHours(1);
		int hour = result.getHour();
		System.out.println(hour);
		assertEquals(0, hour);

		result = localDateTime.minusMinutes(1);
		int minute = result.getMinute();
		System.out.println(minute);
		assertEquals(1, minute);

		result = localDateTime.minusSeconds(1);
		int second = result.getSecond();
		System.out.println(second);
		assertEquals(2, second);
	}

minusTemporalAmount

LocalDateTime Class Java 建立一個 LocalDateTime ，使用 Period 、 Duration 提供指定日期時間減法運算。

	@Test
	public void minusTemporalAmount() {
		LocalDateTime localDateTime = LocalDateTime.of(2023, 8, 3, 1, 2, 3);
		LocalDateTime result = localDateTime.minus(Period.ofYears(1));
		int year = result.getYear();
		System.out.println(year);
		assertEquals(2022, year);

		result = localDateTime.minus(Period.ofMonths(1));
		int month = result.getMonthValue();
		System.out.println(month);
		assertEquals(7, month);

		result = localDateTime.minus(Period.ofDays(1));
		int dayOfMonth = result.getDayOfMonth();
		System.out.println(dayOfMonth);
		assertEquals(2, dayOfMonth);

		result = localDateTime.minus(Duration.ofHours(1));
		int hour = result.getHour();
		System.out.println(hour);
		assertEquals(0, hour);

		result = localDateTime.minus(Duration.ofMinutes(1));
		int minute = result.getMinute();
		System.out.println(minute);
		assertEquals(1, minute);

		result = localDateTime.minus(Duration.ofSeconds(1));
		int second = result.getSecond();
		System.out.println(second);
		assertEquals(2, second);
	}

isBefore

LocalDateTime Class in Java 建立兩個 LocalDateTime ，日期時間比對前後。

	@Test
	public void isBefore() {
		LocalDateTime localDateTime = LocalDateTime.of(2023, 8, 3, 1, 2, 3);
		LocalDateTime localDateTime2 = LocalDateTime.of(2024, 8, 3, 1, 2, 3);
		boolean result = localDateTime.isBefore(localDateTime2);
		System.out.println(result);
		assertTrue(result);

		result = localDateTime2.isBefore(localDateTime);
		System.out.println(result);
		assertFalse(result);
	}

true
false

isAfter

LocalDateTime Class in Java 建立兩個 LocalDateTime ，日期時間比對前後。

	@Test
	public void isAfter() {
		LocalDateTime localDateTime = LocalDateTime.of(2023, 8, 3, 1, 2, 3);
		LocalDateTime localDateTime2 = LocalDateTime.of(2022, 8, 3, 1, 2, 3);
		boolean result = localDateTime.isAfter(localDateTime2);
		System.out.println(result);
		assertTrue(result);
		
		result = localDateTime2.isAfter(localDateTime);
		System.out.println(result);
		assertFalse(result);
	}

true
false

until

LocalDateTime Class in Java 建立兩個 LocalDateTime ，取得日期時間的差值。

	@Test
	public void until() {
		LocalDateTime localDateTime = LocalDateTime.of(2023, 8, 3, 1, 2, 3);
		LocalDateTime localDateTime2 = LocalDateTime.of(2023, 8, 4, 1, 2, 3);
		long result = localDateTime.until(localDateTime2, ChronoUnit.DAYS);
		System.out.println(result);
		assertEquals(1, result);

		result = localDateTime.until(localDateTime2, ChronoUnit.HOURS);
		System.out.println(result);
		assertEquals(24, result);

		result = localDateTime.until(localDateTime2, ChronoUnit.MINUTES);
		System.out.println(result);
		assertEquals(1440, result);
	}

1
24
1440

atZone

LocalDateTime Class in Java 建立一個 LocalDateTime ，使用 ZoneId 取得指定日期時間 ZonedDateTime。

	@Test
	public void atZone() {
		LocalDateTime localDateTime = LocalDateTime.of(2023, 8, 3, 1, 2, 3);
		ZoneId zone = ZoneId.of("UTC+8");
		ZonedDateTime result = localDateTime.atZone(zone);
		System.out.println(result);
		assertEquals("2023-08-03T01:02:03+08:00[UTC+08:00]", result.toString());
	}

2023-08-03T01:02:03+08:00[UTC+08:00]

atOffset

LocalDateTime Class in Java 建立一個 LocalDateTime ，使用 ZoneOffset 取得指定日期時間 OffsetDateTime。

	@Test
	public void atOffset() {
		LocalDateTime localDateTime = LocalDateTime.of(2023, 8, 3, 1, 2, 3);
		OffsetDateTime result = localDateTime.atOffset(ZoneOffset.ofHours(-4));
		System.out.println(result);
		assertEquals("2023-08-03T01:02:03-04:00", result.toString());
	}

2023-08-03T01:02:03-04:00

LocalDateTimeClassTest.java

LocalDateTime Class in Java 新增單元測試，驗證 Java LocalDateTime Class Example 是否符合預期。

package org.ruoxue.java_147.datetime.localdatetime;

import static org.junit.Assert.*;

import java.time.Duration;
import java.time.LocalDateTime;
import java.time.OffsetDateTime;
import java.time.Period;
import java.time.ZoneId;
import java.time.ZoneOffset;
import java.time.ZonedDateTime;
import java.time.temporal.ChronoUnit;

import org.junit.Test;

public class LocalDateTimeClassTest {

	@Test
	public void plus() {
		LocalDateTime localDateTime = LocalDateTime.of(2023, 8, 3, 1, 2, 3);
		LocalDateTime result = localDateTime.plusYears(1);
		int year = result.getYear();
		System.out.println(year);
		assertEquals(2024, year);

		result = localDateTime.plusMonths(1);
		int month = result.getMonthValue();
		System.out.println(month);
		assertEquals(9, month);

		result = localDateTime.plusDays(1);
		int dayOfMonth = result.getDayOfMonth();
		System.out.println(dayOfMonth);
		assertEquals(4, dayOfMonth);

		result = localDateTime.plusHours(1);
		int hour = result.getHour();
		System.out.println(hour);
		assertEquals(2, hour);

		result = localDateTime.plusMinutes(1);
		int minute = result.getMinute();
		System.out.println(minute);
		assertEquals(3, minute);

		result = localDateTime.plusSeconds(1);
		int second = result.getSecond();
		System.out.println(second);
		assertEquals(4, second);
	}

	@Test
	public void plusTemporalAmount() {
		LocalDateTime localDateTime = LocalDateTime.of(2023, 8, 3, 1, 2, 3);
		LocalDateTime result = localDateTime.plus(Period.ofYears(1));
		int year = result.getYear();
		System.out.println(year);
		assertEquals(2024, year);

		result = localDateTime.plus(Period.ofMonths(1));
		int month = result.getMonthValue();
		System.out.println(month);
		assertEquals(9, month);

		result = localDateTime.plus(Period.ofDays(1));
		int dayOfMonth = result.getDayOfMonth();
		System.out.println(dayOfMonth);
		assertEquals(4, dayOfMonth);

		result = localDateTime.plus(Duration.ofHours(1));
		int hour = result.getHour();
		System.out.println(hour);
		assertEquals(2, hour);

		result = localDateTime.plus(Duration.ofMinutes(1));
		int minute = result.getMinute();
		System.out.println(minute);
		assertEquals(3, minute);

		result = localDateTime.plus(Duration.ofSeconds(1));
		int second = result.getSecond();
		System.out.println(second);
		assertEquals(4, second);
	}

	@Test
	public void minus() {
		LocalDateTime localDateTime = LocalDateTime.of(2023, 8, 3, 1, 2, 3);
		LocalDateTime result = localDateTime.minusYears(1);
		int year = result.getYear();
		System.out.println(year);
		assertEquals(2022, year);

		result = localDateTime.minusMonths(1);
		int month = result.getMonthValue();
		System.out.println(month);
		assertEquals(7, month);

		result = localDateTime.minusDays(1);
		int dayOfMonth = result.getDayOfMonth();
		System.out.println(dayOfMonth);
		assertEquals(2, dayOfMonth);

		result = localDateTime.minusHours(1);
		int hour = result.getHour();
		System.out.println(hour);
		assertEquals(0, hour);

		result = localDateTime.minusMinutes(1);
		int minute = result.getMinute();
		System.out.println(minute);
		assertEquals(1, minute);

		result = localDateTime.minusSeconds(1);
		int second = result.getSecond();
		System.out.println(second);
		assertEquals(2, second);
	}

	@Test
	public void minusTemporalAmount() {
		LocalDateTime localDateTime = LocalDateTime.of(2023, 8, 3, 1, 2, 3);
		LocalDateTime result = localDateTime.minus(Period.ofYears(1));
		int year = result.getYear();
		System.out.println(year);
		assertEquals(2022, year);

		result = localDateTime.minus(Period.ofMonths(1));
		int month = result.getMonthValue();
		System.out.println(month);
		assertEquals(7, month);

		result = localDateTime.minus(Period.ofDays(1));
		int dayOfMonth = result.getDayOfMonth();
		System.out.println(dayOfMonth);
		assertEquals(2, dayOfMonth);

		result = localDateTime.minus(Duration.ofHours(1));
		int hour = result.getHour();
		System.out.println(hour);
		assertEquals(0, hour);

		result = localDateTime.minus(Duration.ofMinutes(1));
		int minute = result.getMinute();
		System.out.println(minute);
		assertEquals(1, minute);

		result = localDateTime.minus(Duration.ofSeconds(1));
		int second = result.getSecond();
		System.out.println(second);
		assertEquals(2, second);
	}

	@Test
	public void isBefore() {
		LocalDateTime localDateTime = LocalDateTime.of(2023, 8, 3, 1, 2, 3);
		LocalDateTime localDateTime2 = LocalDateTime.of(2024, 8, 3, 1, 2, 3);
		boolean result = localDateTime.isBefore(localDateTime2);
		System.out.println(result);
		assertTrue(result);

		result = localDateTime2.isBefore(localDateTime);
		System.out.println(result);
		assertFalse(result);
	}

	@Test
	public void isAfter() {
		LocalDateTime localDateTime = LocalDateTime.of(2023, 8, 3, 1, 2, 3);
		LocalDateTime localDateTime2 = LocalDateTime.of(2022, 8, 3, 1, 2, 3);
		boolean result = localDateTime.isAfter(localDateTime2);
		System.out.println(result);
		assertTrue(result);

		result = localDateTime2.isAfter(localDateTime);
		System.out.println(result);
		assertFalse(result);
	}

	@Test
	public void until() {
		LocalDateTime localDateTime = LocalDateTime.of(2023, 8, 3, 1, 2, 3);
		LocalDateTime localDateTime2 = LocalDateTime.of(2023, 8, 4, 1, 2, 3);
		long result = localDateTime.until(localDateTime2, ChronoUnit.DAYS);
		System.out.println(result);
		assertEquals(1, result);

		result = localDateTime.until(localDateTime2, ChronoUnit.HOURS);
		System.out.println(result);
		assertEquals(24, result);

		result = localDateTime.until(localDateTime2, ChronoUnit.MINUTES);
		System.out.println(result);
		assertEquals(1440, result);
	}

	@Test
	public void atZone() {
		LocalDateTime localDateTime = LocalDateTime.of(2023, 8, 3, 1, 2, 3);
		ZoneId zone = ZoneId.of("UTC+8");
		ZonedDateTime result = localDateTime.atZone(zone);
		System.out.println(result);
		assertEquals("2023-08-03T01:02:03+08:00[UTC+08:00]", result.toString());
	}

	@Test
	public void atOffset() {
		LocalDateTime localDateTime = LocalDateTime.of(2023, 8, 3, 1, 2, 3);
		OffsetDateTime result = localDateTime.atOffset(ZoneOffset.ofHours(-4));
		System.out.println(result);
		assertEquals("2023-08-03T01:02:03-04:00", result.toString());
	}
}