Compare LocalDates in Java

Table of Contents

介紹一些常見的方法，像是： compareTo 、 isBefore 、 isAfter 、 isEqual 等方法，比較日期與另一個日期，檢查前後或相等的日期， Java Compare LocalDates 屬於 java.time 套件，日期和時間相關的 API ，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
       |                       +- CompareLocalDatesTest.java

單元測試

Compare LocalDate Instances 提供比較兩個 LocalDate 物件的方法。

compareTo

Compare LocalDateTime Instances 建立兩個 LocalDateTime ，比較日期時間物件，根據比較結果傳回一個整數值，不考慮時區或日曆資訊。

指定的日期時間早於另一個日期時間，則為負整數，如： a 小於 b 傳回 -1 。
指定的日期時間等於另一個日期時間，則為零，如： a 等於 b 傳回 0 。
指定的日期時間晚於另一個日期時間，則為正整數，如： a 大於 b 傳回 1 。

	@Test
	public void compareTo() {
		LocalDate localDate = LocalDate.of(2023, 6, 18);
		LocalDate localDate2 = LocalDate.of(2024, 6, 18);
		int result = localDate.compareTo(localDate2);
		System.out.println(result);
		assertThat(result).isLessThan(0);

		localDate = LocalDate.of(2023, 6, 18);
		localDate2 = LocalDate.of(2023, 6, 18);
		result = localDate.compareTo(localDate2);
		System.out.println(result);
		assertThat(result).isEqualTo(0);

		localDate = LocalDate.of(2023, 6, 18);
		localDate2 = LocalDate.of(2022, 6, 18);
		result = localDate.compareTo(localDate2);
		System.out.println(result);
		assertThat(result).isGreaterThan(0);
	}

-1
0
1

isBefore

Compare LocalDate Instances 建立兩個 LocalDate ，檢查指定的日期是否早於另一個日期。

	@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);
		assertThat(result).isTrue();

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

true
false

isAfter

Compare LocalDate Instances 建立兩個 LocalDate ，檢查指定的日期是否晚於另一個日期。

	@Test
	public void isAfter() {
		LocalDate localDate = LocalDate.of(2023, 6, 1);
		LocalDate localDate2 = LocalDate.of(2022, 6, 18);
		boolean result = localDate.isAfter(localDate2);
		System.out.println(result);
		assertThat(result).isTrue();

		result = localDate2.isAfter(localDate);
		System.out.println(result);
		assertThat(result).isFalse();
	}

true
false

equals

Compare Two LocalDate Instances 建立兩個 LocalDate ，檢查指定的日期是否等於另一個日期。

	@Test
	public void equals() {
		LocalDate localDate = LocalDate.of(2023, 6, 18);
		LocalDate localDate2 = LocalDate.of(2023, 6, 18);
		boolean result = localDate.equals(localDate2);
		System.out.println(result);
		assertThat(result).isTrue();

		result = localDate2.equals(localDate);
		System.out.println(result);
		assertThat(result).isTrue();
	}

true
false

isEqual

Compare Two LocalDate Instances 建立兩個 LocalDate ，檢查指定的日期是否等於另一個日期。

	@Test
	public void isEqual() {
		LocalDate localDate = LocalDate.of(2023, 6, 18);
		LocalDate localDate2 = LocalDate.of(2023, 6, 18);
		boolean result = localDate.isEqual(localDate2);
		System.out.println(result);
		assertThat(result).isTrue();

		result = localDate2.isEqual(localDate);
		System.out.println(result);
		assertThat(result).isTrue();
	}

true
false

CompareLocalDatesTest.java

Compare Two LocalDate Instances 新增單元測試，驗證是否符合預期。

package org.ruoxue.java_147.datetime.localdate;

import static org.assertj.core.api.Assertions.assertThat;

import java.time.LocalDate;

import org.junit.Test;

public class CompareLocalDatesTest {

	@Test
	public void compareTo() {
		LocalDate localDate = LocalDate.of(2023, 6, 18);
		LocalDate localDate2 = LocalDate.of(2024, 6, 18);
		int result = localDate.compareTo(localDate2);
		System.out.println(result);
		assertThat(result).isLessThan(0);

		localDate = LocalDate.of(2023, 6, 18);
		localDate2 = LocalDate.of(2023, 6, 18);
		result = localDate.compareTo(localDate2);
		System.out.println(result);
		assertThat(result).isEqualTo(0);

		localDate = LocalDate.of(2023, 6, 18);
		localDate2 = LocalDate.of(2022, 6, 18);
		result = localDate.compareTo(localDate2);
		System.out.println(result);
		assertThat(result).isGreaterThan(0);
	}

	@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);
		assertThat(result).isTrue();

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

	@Test
	public void isAfter() {
		LocalDate localDate = LocalDate.of(2023, 6, 1);
		LocalDate localDate2 = LocalDate.of(2022, 6, 18);
		boolean result = localDate.isAfter(localDate2);
		System.out.println(result);
		assertThat(result).isTrue();

		result = localDate2.isAfter(localDate);
		System.out.println(result);
		assertThat(result).isFalse();
	}

	@Test
	public void equals() {
		LocalDate localDate = LocalDate.of(2023, 6, 18);
		LocalDate localDate2 = LocalDate.of(2023, 6, 18);
		boolean result = localDate.equals(localDate2);
		System.out.println(result);
		assertThat(result).isTrue();

		result = localDate2.equals(localDate);
		System.out.println(result);
		assertThat(result).isTrue();
	}
	
	@Test
	public void isEqual() {
		LocalDate localDate = LocalDate.of(2023, 6, 18);
		LocalDate localDate2 = LocalDate.of(2023, 6, 18);
		boolean result = localDate.isEqual(localDate2);
		System.out.println(result);
		assertThat(result).isTrue();

		result = localDate2.isEqual(localDate);
		System.out.println(result);
		assertThat(result).isTrue();
	}
}