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Java LocalDate Methods - Java 147

Java LocalDate Methods – Java 147

Java LocalDate Methods

隨著 Java 8 的出現，建立日期的方式重新被定義，相對於 java.util 舊的 API ， java.time 中的新日期和時間 API 可以更加便利與輕鬆地使用， LocalDate 是一個不可變、線程安全的物件，只能儲存日期，不能包含時間，介紹常見的 now 、 of 、 get 、 with 等方法， LocalDate Java Methods 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
       |                       +- LocalDateMethodsTest.java

單元測試

LocalDate Methods Java 提供目前日期、建立、取得等操作 LocalDate 。

now

LocalDate Methods Java 建立一個 LocalDate ，提供目前日期。

	@Test
	public void now() {
		LocalDate localDate = LocalDate.now();
		System.out.println(localDate);

		ZoneId zone = ZoneId.of("America/Chicago");
		localDate = LocalDate.now(zone);
		System.out.println(localDate);

		zone = ZoneId.of("UTC-5");
		Clock clock = Clock.system(zone);
		localDate = LocalDate.now(clock);
		System.out.println(localDate);

		zone = ZoneId.of("Etc/GMT+5");
		localDate = LocalDate.now(zone);
		System.out.println(localDate);
	}
2023-06-25
2023-06-24
2023-06-24

of

LocalDate Methods Java 建立一個 LocalDate ，建立指定日期。

	@Test
	public void of() {
		LocalDate localDate = LocalDate.of(2023, 6, 18);
		System.out.println(localDate);
		assertEquals("2023-06-18", localDate.toString());

		long epochDay = localDate.toEpochDay();
		System.out.println(epochDay);
		assertEquals(19526, epochDay);

		localDate = LocalDate.of(2023, Month.JUNE, 19);
		System.out.println(localDate);
		assertEquals("2023-06-19", localDate.toString());

		localDate = LocalDate.ofYearDay(2023, 171);
		System.out.println(localDate);
		assertEquals("2023-06-20", localDate.toString());

		localDate = LocalDate.ofEpochDay(19529);
		System.out.println(localDate);
		assertEquals("2023-06-21", localDate.toString());
	}
2023-06-18
19526
2023-06-19
2023-06-20
2023-06-21

get

LocalDate Methods Java 建立一個 LocalDate ，取得指定欄位，如：年、月、日等。

	@Test
	public void get() {
		LocalDate localDate = LocalDate.of(2023, 6, 18);
		int year = localDate.get(ChronoField.YEAR);
		System.out.println(year);
		assertEquals(2023, year);

		int month = localDate.get(ChronoField.MONTH_OF_YEAR);
		System.out.println(month);
		assertEquals(6, month);

		int dayOfMonth = localDate.get(ChronoField.DAY_OF_MONTH);
		System.out.println(dayOfMonth);
		assertEquals(18, dayOfMonth);

		int dayOfWeek = localDate.get(ChronoField.DAY_OF_WEEK);
		System.out.println(dayOfWeek);
		assertEquals(7, dayOfWeek);

		int dayOfYear = localDate.get(ChronoField.DAY_OF_YEAR);
		System.out.println(dayOfYear);
		assertEquals(169, dayOfYear);
	}
2023
6
18
7
169

getValue

LocalDate Methods in Java 建立一個 LocalDate ，取得指定欄位，如：年、月、日等。

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

		int month = localDate.getMonthValue();
		System.out.println(month);
		assertEquals(6, month);

		int dayOfMonth = localDate.getDayOfMonth();
		System.out.println(dayOfMonth);
		assertEquals(18, dayOfMonth);

		int dayOfWeek = localDate.getDayOfWeek().getValue();
		System.out.println(dayOfWeek);
		assertEquals(7, dayOfWeek);

		int dayOfYear = localDate.getDayOfYear();
		System.out.println(dayOfYear);
		assertEquals(169, dayOfYear);
	}
2023
6
18
7
169

with

LocalDate Methods in Java 建立一個 LocalDate ，調整指定欄位，如：年、月、日等，會傳回新物件。

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

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

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

withTemporalAdjuster

LocalDate Methods in Java 建立一個 LocalDate ，使用 TemporalAdjuster 調整指定欄位，如：年、月、日等，會傳回新物件。

	@Test
	public void withTemporalAdjuster() {
		LocalDate localDate = LocalDate.of(2023, 6, 18);
		LocalDate result = localDate.with(ChronoField.DAY_OF_MONTH, 19);
		System.out.println(result);
		assertEquals("2023-06-19", result.toString());

		result = localDate.with(TemporalAdjusters.next(DayOfWeek.SATURDAY));
		System.out.println(result);
		assertEquals("2023-06-24", result.toString());

		result = localDate.with(TemporalAdjusters.lastDayOfMonth());
		System.out.println(result);
		assertEquals("2023-06-30", result.toString());

		TemporalAdjuster temporalAdjuster = t -> t.plus(Period.ofDays(14));
		result = localDate.with(temporalAdjuster);
		System.out.println(result);
		assertEquals("2023-07-02", result.toString());
	}
2023-06-19
2023-06-24
2023-06-30
2023-07-02

LocalDateMethodsTest.java

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

package org.ruoxue.java_147.datetime.localdate;

import static org.junit.Assert.*;

import java.time.Clock;
import java.time.DayOfWeek;
import java.time.LocalDate;
import java.time.Month;
import java.time.Period;
import java.time.ZoneId;
import java.time.temporal.ChronoField;
import java.time.temporal.TemporalAdjuster;
import java.time.temporal.TemporalAdjusters;

import org.junit.Test;

public class LocalDateMethodsTest {

	@Test
	public void now() {
		LocalDate localDate = LocalDate.now();
		System.out.println(localDate);

		ZoneId zone = ZoneId.of("America/Chicago");
		localDate = LocalDate.now(zone);
		System.out.println(localDate);

		zone = ZoneId.of("UTC-5");
		Clock clock = Clock.system(zone);
		localDate = LocalDate.now(clock);
		System.out.println(localDate);

		zone = ZoneId.of("Etc/GMT+5");
		localDate = LocalDate.now(zone);
		System.out.println(localDate);
	}

	@Test
	public void of() {
		LocalDate localDate = LocalDate.of(2023, 6, 18);
		System.out.println(localDate);
		assertEquals("2023-06-18", localDate.toString());

		long epochDay = localDate.toEpochDay();
		System.out.println(epochDay);
		assertEquals(19526, epochDay);

		localDate = LocalDate.of(2023, Month.JUNE, 19);
		System.out.println(localDate);
		assertEquals("2023-06-19", localDate.toString());

		localDate = LocalDate.ofYearDay(2023, 171);
		System.out.println(localDate);
		assertEquals("2023-06-20", localDate.toString());

		localDate = LocalDate.ofEpochDay(19529);
		System.out.println(localDate);
		assertEquals("2023-06-21", localDate.toString());
	}

	@Test
	public void get() {
		LocalDate localDate = LocalDate.of(2023, 6, 18);
		int year = localDate.get(ChronoField.YEAR);
		System.out.println(year);
		assertEquals(2023, year);

		int month = localDate.get(ChronoField.MONTH_OF_YEAR);
		System.out.println(month);
		assertEquals(6, month);

		int dayOfMonth = localDate.get(ChronoField.DAY_OF_MONTH);
		System.out.println(dayOfMonth);
		assertEquals(18, dayOfMonth);

		int dayOfWeek = localDate.get(ChronoField.DAY_OF_WEEK);
		System.out.println(dayOfWeek);
		assertEquals(7, dayOfWeek);

		int dayOfYear = localDate.get(ChronoField.DAY_OF_YEAR);
		System.out.println(dayOfYear);
		assertEquals(169, dayOfYear);
	}

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

		int month = localDate.getMonthValue();
		System.out.println(month);
		assertEquals(6, month);

		int dayOfMonth = localDate.getDayOfMonth();
		System.out.println(dayOfMonth);
		assertEquals(18, dayOfMonth);

		int dayOfWeek = localDate.getDayOfWeek().getValue();
		System.out.println(dayOfWeek);
		assertEquals(7, dayOfWeek);

		int dayOfYear = localDate.getDayOfYear();
		System.out.println(dayOfYear);
		assertEquals(169, dayOfYear);
	}

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

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

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

	@Test
	public void withTemporalAdjuster() {
		LocalDate localDate = LocalDate.of(2023, 6, 18);
		LocalDate result = localDate.with(ChronoField.DAY_OF_MONTH, 19);
		System.out.println(result);
		assertEquals("2023-06-19", result.toString());

		result = localDate.with(TemporalAdjusters.next(DayOfWeek.SATURDAY));
		System.out.println(result);
		assertEquals("2023-06-24", result.toString());

		result = localDate.with(TemporalAdjusters.lastDayOfMonth());
		System.out.println(result);
		assertEquals("2023-06-30", result.toString());

		TemporalAdjuster temporalAdjuster = t -> t.plus(Period.ofDays(14));
		result = localDate.with(temporalAdjuster);
		System.out.println(result);
		assertEquals("2023-07-02", result.toString());
	}
}

心得分享

LocalDate Functions in Java 是一個不可變的類別，表示日期，預設格式為 yyyy-mm-dd， 實現 ChronoLocalDate 接口， LocalDate Methods in Java 提供 now 、 of 、 get 、 with 等常見方法的操作範例。

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