Java LocalDate（）、LocalDateTime（）、ZonedDateTime（）、Calendar（）、およびDate（）チュートリアル

公開: 2020-07-18

Javaでは、現在の時刻をエポック時刻に変換する方法と、2つのJava日付インスタンス間の差を計算する方法のチュートリアルを以前に公開しました。

このチュートリアルでは、以下のすべてのJavaDateおよびCalendarAPIについて説明します。

LocalDate（）：

LocalDateは、日付を表す不変の日時オブジェクトであり、多くの場合、年-月-日と見なされます。曜日、曜日、週などの他の日付フィールドにもアクセスできます。

LocalDate Java API

LocalDateTime（）：

LocalDateTimeは、日時を表す不変の日時オブジェクトであり、多くの場合、年-月-日-時-分-秒と見なされます。

LocalDateTime Java API

ZonedDateTime（）：

ZonedDateTimeは、タイムゾーンを使用した日時の不変の表現です。このクラスは、すべての日付と時刻のフィールドをナノ秒の精度で格納し、タイムゾーンを格納します。ゾーンオフセットは、あいまいなローカル日時の処理に使用されます。

ZonedDateTime Java API

カレンダー（）：

Calendarクラスは、特定の瞬間とYEAR、MONTH、DAY_OF_MONTH、HOURなどの一連のカレンダーフィールドを変換したり、日付の取得などのカレンダーフィールドを操作したりするためのメソッドを提供する抽象クラスです。来週の。瞬間は、1970年1月1日00：00：00.000 GMT（グレゴリオ暦）のエポックからのオフセットであるミリ秒の値で表すことができます。

日にち（）：

クラスDateは、ミリ秒の精度で特定の瞬間を表します。

始めましょう：

ファイルの作成：CrunchifyDateTimeCalendarTutorial.java

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package crunchify.com.tutorials;

import java.text.ParseException;

import java.text.SimpleDateFormat;

import java.time.LocalDate;

import java.time.LocalDateTime;

import java.time.Period;

import java.time.ZonedDateTime;

import java.time.temporal.ChronoUnit;

import java.util.Calendar;

import java.util.Date;

import java.util.GregorianCalendar;

/**

* @author Crunchify.com

* version: 1.0

* Tutorial: Java LocalDate(), LocalDateTime(), ZonedDateTime(), Calendar() and Date() Tutorial

public class CrunchifyDateTimeCalendarTutorial {

public static void main(String[] args) {

// ************************************************ LocalDate **********************************************

// LocalDate is an immutable date-time object that represents a date, often viewed as year-month-day. Other date fields, such as

// day-of-year, day-of-week and week-of-year, can also be accessed. For example, the value "2nd October 2007" can be stored in a

// LocalDate.

crunchifyLog("============ LocalDate test Start ============");

LocalDate currentLocalDate = LocalDate.now();

LocalDate currentLocalNewDate = LocalDate.of(2019, 1, 11);

crunchifyLog("LocalDate.now(): " + currentLocalDate);

crunchifyLog("LocalDate.of(2019, 1, 11): " + currentLocalNewDate);

// Period: A date-based amount of time in the ISO-8601 calendar system, such as '2 years, 3 months and 4 days'.

Period period = Period.between(currentLocalDate, currentLocalNewDate);

crunchifyLog("Month differences: " + period.getMonths());

if (period.getMonths() <= -3) {

crunchifyLog("result: " + currentLocalNewDate + " is older than 3 months!");

}

LocalDate currentLocalDateNew = LocalDate.now();

LocalDate threeMonthAgo = LocalDate.now().plusMonths(-3);

crunchifyLog("LocalDate.now(): " + currentLocalDateNew);

crunchifyLog("LocalDate.now().plusMonths(-3): " + threeMonthAgo);

LocalDate crunchifyLocalDate = LocalDate.of(2019, 1, 11);

// is this date older than 6 months?

if (crunchifyLocalDate.isBefore(threeMonthAgo)) {

crunchifyLog("crunchifyLocalDate.isBefore(threeMonthAgo) result: " + crunchifyLocalDate + " is older than 3 months!");

}

crunchifyLog("============ LocalDate test End ============ \n");

// ************************************************ LocalDateTime **********************************************

// LocalDateTime is an immutable date-time object that represents a date-time, often viewed as year-month-day-hour-minute-second.

// Other date and time fields, such as day-of-year, day-of-week and week-of-year, can also be accessed. Time is represented to

// nanosecond precision. For example, the value "2nd October 2007 at 13:45.30.123456789" can be stored in a LocalDateTime.

crunchifyLog("============ LocalDateTime test Start ============");

LocalDateTime currentDate2 = LocalDateTime.now();

LocalDateTime fourMonthAgo = LocalDateTime.now().plusMonths(-4);

crunchifyLog("LocalDateTime.now(): " + currentLocalDate);

crunchifyLog("LocalDateTime.now().plusMonths(-4): " + fourMonthAgo);

LocalDateTime newDate2 = LocalDateTime.of(2019, 7, 1, 0, 0, 0);

// Checks if this date-time is before the specified date-time.

if (newDate2.isBefore(fourMonthAgo)) {

crunchifyLog("isBefore() result: " + newDate2 + " is older than 4 months!");

}

long findGap = ChronoUnit.MONTHS.between(currentDate2, newDate2);

crunchifyLog(findGap);

if (findGap <= -4) {

crunchifyLog("findGap result: " + newDate2 + " is older than 4 months!");

}

crunchifyLog("============ LocalDateTime test End ============ \n");

// ************************************************ ZonedDateTime **********************************************

// ZonedDateTime is an immutable representation of a date-time with a time-zone. This class stores all date and time fields, to a

// precision of nanoseconds, and a time-zone, with a zone offset used to handle ambiguous local date-times. For example, the value

// "2nd October 2007 at 13:45.30.123456789 +02:00 in the Europe/Paris time-zone" can be stored in a ZonedDateTime.

crunchifyLog("============ ZonedDateTime test Start ============");

ZonedDateTime crunchifyNow = ZonedDateTime.now();

ZonedDateTime thirtyDaysAgo = crunchifyNow.plusDays(-30);

crunchifyLog("ZonedDateTime.now() :" + crunchifyNow);

crunchifyLog("now.plusDays(-30) :" + thirtyDaysAgo);

ZonedDateTime fiftyDaysAgo = crunchifyNow.plusDays(-50);

crunchifyLog("now.plusDays(-50) :" + fiftyDaysAgo);

if (fiftyDaysAgo.isBefore(thirtyDaysAgo)) {

crunchifyLog("fiftyDaysAgo.isBefore(thirtyDaysAgo): " + thirtyDaysAgo + " is older than 30 days!");

}

// ChronoUnit: A standard set of date periods units.

// This set of units provide unit-based access to manipulate a date, time or date-time. The standard set of units can be extended by

// implementing TemporalUnit.

long crunchifyBetween = ChronoUnit.DAYS.between(crunchifyNow, fiftyDaysAgo);

crunchifyLog(crunchifyBetween);

if (crunchifyBetween < -30) {

crunchifyLog("crunchifyBetween < -30 result: " + thirtyDaysAgo + " is older than 30 days!");

}

crunchifyLog("============ ZonedDateTime test End ============ \n");

// ************************************************ Calendar **********************************************

// The Calendar class is an abstract class that provides methods for converting between a specific instant in time and a set of

// calendar fields such as YEAR, MONTH, DAY_OF_MONTH, HOUR, and so on, and for manipulating the calendar fields, such as getting the

// date of the next week. An instant in time can be represented by a millisecond value that is an offset from the Epoch, January 1,

// 1970 00:00:00.000 GMT (Gregorian).

crunchifyLog("============ Calendar test Start ============");

SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");

Calendar fiveMonthsAgo = Calendar.getInstance();

crunchifyLog("Calendar.getInstance(): " + sdf.format(fiveMonthsAgo.getTime()));

// Adds or subtracts the specified amount of time to the given calendar field, based on the calendar's rules.

fiveMonthsAgo.add(Calendar.MONTH, -5);

crunchifyLog("Calendar.MONTH, -5): " + sdf.format(fiveMonthsAgo.getTime()));

Calendar crunchifyCalendar = new GregorianCalendar(2019, 7, 11);

if (crunchifyCalendar.before(threeMonthAgo)) {

crunchifyLog("crunchifyCalendar.before(threeMonthAgo) result : " + sdf.format(crunchifyCalendar.getTime()) + " is older than 5 months");

}

crunchifyLog("============ Calendar test End ============ \n");

// ************************************************ Date **********************************************

// Date: The class Date represents a specific instant in time, with millisecond precision.

crunchifyLog("============ Date test Start ============");

SimpleDateFormat sdf5 = new SimpleDateFormat("yyyy-MM-dd");

Date crunchifyToday = new Date();

crunchifyLog("new Date(): " + sdf5.format(crunchifyToday));

Calendar twentyDaysAgo = Calendar.getInstance();

twentyDaysAgo.add(Calendar.DAY_OF_MONTH, -20);

Date thirtyDaysAgoDate = twentyDaysAgo.getTime();

crunchifyLog("twentyDaysAgo.getTime(): " + sdf5.format(thirtyDaysAgoDate));

Date crunchifyNewDate = null;

try {

// Parses text from the beginning of the given string to produce a date. The method may not use the entire text of the given string.

crunchifyNewDate = sdf5.parse("2019-07-11");

} catch (ParseException e) {

e.printStackTrace();

}

if (crunchifyNewDate.before(thirtyDaysAgoDate)) {

crunchifyLog(sdf.format(crunchifyNewDate) + " is older than 30 days!");

}

crunchifyLog("============ Date test End ============ \n");

}

private static void crunchifyLog(Object crunchifyString) {

System.out.println(crunchifyString);

}

IntelliJIDEAで実行するだけです。

コンソール出力。

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CrunchifyDateTimeCalendarTutorial

============ LocalDate test Start ============

LocalDate . now ( ) : 2020 - 07 - 18

LocalDate . of ( 2019 , 1 , 11 ) : 2019 - 01 - 11

Month differences : - 6

result : 2019 - 01 - 11 is older than 3 months !

LocalDate . now ( ) : 2020 - 07 - 18

LocalDate . now ( ) . plusMonths ( - 3 ) : 2020 - 04 - 18

crunchifyLocalDate . isBefore ( threeMonthAgo ) result : 2019 - 01 - 11 is older than 3 months !

============ LocalDate test End ============

============ LocalDateTime test Start ============

LocalDateTime . now ( ) : 2020 - 07 - 18

LocalDateTime . now ( ) . plusMonths ( - 4 ) : 2020 - 03 - 18T10 : 27 : 28.285711

isBefore ( ) result : 2019 - 07 - 01T00 : 00 is older than 4 months !

- 12

findGap result : 2019 - 07 - 01T00 : 00 is older than 4 months !

============ LocalDateTime test End ============

============ ZonedDateTime test Start ============

ZonedDateTime . now ( ) : 2020 - 07 - 18T10 : 27 : 28.286147 - 05 : 00 [ America / Chicago ]

now . plusDays ( - 30 ) : 2020 - 06 - 18T10 : 27 : 28.286147 - 05 : 00 [ America / Chicago ]

now . plusDays ( - 50 ) : 2020 - 05 - 29T10 : 27 : 28.286147 - 05 : 00 [ America / Chicago ]

fiftyDaysAgo . isBefore ( thirtyDaysAgo ) : 2020 - 06 - 18T10 : 27 : 28.286147 - 05 : 00 [ America / Chicago ] is older than 30 days !

- 50

crunchifyBetween < - 30 result : 2020 - 06 - 18T10 : 27 : 28.286147 - 05 : 00 [ America / Chicago ] is older than 30 days !

============ ZonedDateTime test End ============

============ Calendar test Start ============

Calendar . getInstance ( ) : 2020 - 07 - 18

Calendar . MONTH , - 5 ) : 2020 - 02 - 18

============ Calendar test End ============

============ Date test Start ============

new Date ( ) : 2020 - 07 - 18

twentyDaysAgo . getTime ( ) : 2020 - 06 - 28

2019 - 07 - 11 is older than 30 days !

============ Date test End ============

Process finished with exit code 0

このチュートリアルが、これらすべてのDate and TimeAPIの利用に役立つことを願っています。