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Java LocalDate Class - Java 147

Java LocalDate Class – Java 147

Java LocalDate Class

新的日期 API 跟以往複雜的日期 API 有著很大的不同，像是將區域分離，讓物件功能更加專職，簡化了許多日期的操作方法，提供增加、減少、比較日期、或兩個日期差值的方法， LocalDate 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
       |                   +- localdate
       |                       +- LocalDateClassTest.java

單元測試

LocalDate Class Java 提供日期加減、比較前後等操作 LocalDate 。

plus

LocalDate Class Java 建立一個 LocalDate ，提供指定日期加法運算。

	@Test
	public void plus() {
		LocalDate localDate = LocalDate.of(2023, 6, 18);
		LocalDate result = localDate.plusYears(1);
		int year = result.getYear();
		System.out.println(year);
		assertEquals(2024, year);

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

		result = localDate.plusDays(1);
		int dayOfMonth = result.getDayOfMonth();
		System.out.println(dayOfMonth);
		assertEquals(19, dayOfMonth);
	}
2024
7
19

plusTemporalAmount

LocalDate Class Java 建立一個 LocalDate ，使用 Period 提供指定日期加法運算。

	@Test
	public void plusTemporalAmount() {
		LocalDate localDate = LocalDate.of(2023, 6, 18);
		LocalDate result = localDate.plus(Period.ofYears(1));
		int year = result.getYear();
		System.out.println(year);
		assertEquals(2024, year);

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

		result = localDate.plus(Period.ofDays(1));
		int dayOfMonth = result.getDayOfMonth();
		System.out.println(dayOfMonth);
		assertEquals(19, dayOfMonth);
	}
2024
7
19

minus

LocalDate Class Java 建立一個 LocalDate ，提供指定日期減法運算。

	@Test
	public void minus() {
		LocalDate localDate = LocalDate.of(2023, 6, 18);
		LocalDate result = localDate.minusYears(1);
		int year = result.getYear();
		System.out.println(year);
		assertEquals(2022, year);

		result = localDate.minusMonths(1);
		int month = result.getMonthValue();
		System.out.println(month);
		assertEquals(5, month);

		result = localDate.minusDays(1);
		int dayOfMonth = result.getDayOfMonth();
		System.out.println(dayOfMonth);
		assertEquals(17, dayOfMonth);
	}
2022
5
17

minusTemporalAmount

LocalDate Class Java 建立一個 LocalDate ，使用 Period 提供指定日期減法運算。

	@Test
	public void minusTemporalAmount() {
		LocalDate localDate = LocalDate.of(2023, 6, 18);
		LocalDate result = localDate.minus(Period.ofYears(1));
		int year = result.getYear();
		System.out.println(year);
		assertEquals(2022, year);

		result = localDate.minus(Period.ofMonths(1));
		int month = result.getMonthValue();
		System.out.println(month);
		assertEquals(5, month);

		result = localDate.minus(Period.ofDays(1));
		int dayOfMonth = result.getDayOfMonth();
		System.out.println(dayOfMonth);
		assertEquals(17, dayOfMonth);
	}
2022
5
17

isBefore

LocalDate Class in Java 建立兩個 LocalDate ，日期比對前後。

	@Test
	public void isBefore() {
		LocalDate localDate = LocalDate.of(2023, 6, 18);
		LocalDate localDate2 = LocalDate.of(2024, 6, 18);
		boolean result = localDate.isBefore(localDate2);
		System.out.println(result);
		assertTrue(result);

		result = localDate2.isBefore(localDate);
		System.out.println(result);
		assertFalse(result);
	}
true
false

isAfter

LocalDate Class in Java 建立兩個 LocalDate ，日期比對前後。

	@Test
	public void isAfter() {
		LocalDate localDate = LocalDate.of(2023, 6, 18);
		LocalDate localDate2 = LocalDate.of(2022, 6, 18);
		boolean result = localDate.isAfter(localDate2);
		System.out.println(result);
		assertTrue(result);
		
		result = localDate2.isAfter(localDate);
		System.out.println(result);
		assertFalse(result);
	}
true
false

until

LocalDate Class in Java 建立兩個 LocalDate ，取得日期的差值。

	@Test
	public void until() {
		LocalDate localDate = LocalDate.of(2023, 6, 18);
		LocalDate localDate2 = LocalDate.of(2024, 6, 18);
		long result = localDate.until(localDate2, ChronoUnit.YEARS);
		System.out.println(result);
		assertEquals(1, result);

		result = localDate.until(localDate2, ChronoUnit.MONTHS);
		System.out.println(result);
		assertEquals(12, result);

		result = localDate.until(localDate2, ChronoUnit.DAYS);
		System.out.println(result);
		assertEquals(366, result);
	}
1
12
366

atStartOfDay

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

	@Test
	public void atStartOfDay() {
		LocalDate localDate = LocalDate.of(2023, 6, 18);
		ZoneId zone = ZoneId.of("UTC+8");
		ZonedDateTime result = localDate.atStartOfDay(zone);
		System.out.println(result);
		assertEquals("2023-06-18T00:00+08:00[UTC+08:00]", result.toString());
	}
2023-06-18T00:00+08:00[UTC+08:00]

LocalDateClassTest.java

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

package org.ruoxue.java_147.datetime.localdate;

import static org.junit.Assert.*;

import java.time.LocalDate;
import java.time.Period;
import java.time.ZoneId;
import java.time.ZonedDateTime;
import java.time.temporal.ChronoUnit;

import org.junit.Test;

public class LocalDateClassTest {

	@Test
	public void plus() {
		LocalDate localDate = LocalDate.of(2023, 6, 18);
		LocalDate result = localDate.plusYears(1);
		int year = result.getYear();
		System.out.println(year);
		assertEquals(2024, year);

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

		result = localDate.plusDays(1);
		int dayOfMonth = result.getDayOfMonth();
		System.out.println(dayOfMonth);
		assertEquals(19, dayOfMonth);
	}

	@Test
	public void plusTemporalAmount() {
		LocalDate localDate = LocalDate.of(2023, 6, 18);
		LocalDate result = localDate.plus(Period.ofYears(1));
		int year = result.getYear();
		System.out.println(year);
		assertEquals(2024, year);

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

		result = localDate.plus(Period.ofDays(1));
		int dayOfMonth = result.getDayOfMonth();
		System.out.println(dayOfMonth);
		assertEquals(19, dayOfMonth);
	}

	@Test
	public void minus() {
		LocalDate localDate = LocalDate.of(2023, 6, 18);
		LocalDate result = localDate.minusYears(1);
		int year = result.getYear();
		System.out.println(year);
		assertEquals(2022, year);

		result = localDate.minusMonths(1);
		int month = result.getMonthValue();
		System.out.println(month);
		assertEquals(5, month);

		result = localDate.minusDays(1);
		int dayOfMonth = result.getDayOfMonth();
		System.out.println(dayOfMonth);
		assertEquals(17, dayOfMonth);
	}

	@Test
	public void minusTemporalAmount() {
		LocalDate localDate = LocalDate.of(2023, 6, 18);
		LocalDate result = localDate.minus(Period.ofYears(1));
		int year = result.getYear();
		System.out.println(year);
		assertEquals(2022, year);

		result = localDate.minus(Period.ofMonths(1));
		int month = result.getMonthValue();
		System.out.println(month);
		assertEquals(5, month);

		result = localDate.minus(Period.ofDays(1));
		int dayOfMonth = result.getDayOfMonth();
		System.out.println(dayOfMonth);
		assertEquals(17, dayOfMonth);
	}

	@Test
	public void isBefore() {
		LocalDate localDate = LocalDate.of(2023, 6, 18);
		LocalDate localDate2 = LocalDate.of(2024, 6, 18);
		boolean result = localDate.isBefore(localDate2);
		System.out.println(result);
		assertTrue(result);

		result = localDate2.isBefore(localDate);
		System.out.println(result);
		assertFalse(result);
	}

	@Test
	public void isAfter() {
		LocalDate localDate = LocalDate.of(2023, 6, 18);
		LocalDate localDate2 = LocalDate.of(2022, 6, 18);
		boolean result = localDate.isAfter(localDate2);
		System.out.println(result);
		assertTrue(result);
		
		result = localDate2.isAfter(localDate);
		System.out.println(result);
		assertFalse(result);
	}

	@Test
	public void until() {
		LocalDate localDate = LocalDate.of(2023, 6, 18);
		LocalDate localDate2 = LocalDate.of(2024, 6, 18);
		long result = localDate.until(localDate2, ChronoUnit.YEARS);
		System.out.println(result);
		assertEquals(1, result);

		result = localDate.until(localDate2, ChronoUnit.MONTHS);
		System.out.println(result);
		assertEquals(12, result);

		result = localDate.until(localDate2, ChronoUnit.DAYS);
		System.out.println(result);
		assertEquals(366, result);
	}

	@Test
	public void atStartOfDay() {
		LocalDate localDate = LocalDate.of(2023, 6, 18);
		ZoneId zone = ZoneId.of("UTC+8");
		ZonedDateTime result = localDate.atStartOfDay(zone);
		System.out.println(result);
		assertEquals("2023-06-18T00:00+08:00[UTC+08:00]", result.toString());
	}
}

心得分享

Java LocalDate Class Example 屬於 java.time ，物件的值不會被改變，可以同時在不同的執行緒下被使用， LocalDate Class in Java 提供 plus 、 minus 、 isBefore 、 isAfter 、 until 等操作範例。

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