Java LocalDate(), LocalDateTime(), ZonedDateTime(), Calendar() 和 Date() 教程
已發表: 2020-07-18
在 Java 上，我們曾經發布過如何將當前時間轉換為紀元時間以及如何計算兩個 Java 日期實例之間的差異的教程。
在本教程中，我們將介紹以下所有 Java 日期和日曆 API：
本地日期（）：
LocalDate 是一個不可變的日期時間對象，它表示一個日期，通常被視為年-月-日。 也可以訪問其他日期字段，例如一年中的某一天、一周中的某一天和一年中的一周。
本地日期時間（）：
LocalDateTime 是一個不可變的日期時間對象，它表示日期時間，通常被視為年-月-日-時-分-秒。
分區日期時間（）：
ZonedDateTime 是具有時區的日期時間的不可變表示。 此類存儲所有日期和時間字段，精度為納秒和時區，區域偏移用於處理不明確的本地日期時間。
日曆（）：
Calendar 類是一個抽像類，它提供了在特定時刻和一組日曆字段（例如 YEAR、MONTH、DAY_OF_MONTH、HOUR 等）之間進行轉換的方法，以及用於操作日曆字段（例如獲取日期）的方法下週的。 時間的瞬間可以用毫秒值表示，該值是從 1970 年 1 月 1 日 00:00:00.000 GMT（格里高利）紀元的偏移量。
日期（）：
Date 類表示特定的時間瞬間，精度為毫秒。
讓我們開始吧：
創建文件：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); } } |
只需在 IntelliJ IDEA 中運行它：
控制台輸出。
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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 |
我希望本教程可以幫助您利用所有這些日期和時間 API。