Esercitazione Java LocalDate(), LocalDateTime(), ZonedDateTime(), Calendar() e Date()

Pubblicato: 2020-07-18

Esercitazione Java LocalDate(), LocalDateTime(), ZonedDateTime(), Calendar() e Date()

Su Java, abbiamo pubblicato i tutorial Come convertire l'ora corrente in Epoch Time e Come calcolare la differenza tra due istanze di data Java qualche tempo fa.

In questo tutorial esamineremo tutte le seguenti API Java Date e Calendar:

Data Locale():

LocalDate è un oggetto data-ora immutabile che rappresenta una data, spesso vista come anno-mese-giorno. È possibile accedere anche ad altri campi della data, come giorno dell'anno, giorno della settimana e settimana dell'anno.

API Java LocalDate

LocalDateTime():

LocalDateTime è un oggetto data-ora immutabile che rappresenta una data-ora, spesso vista come anno-mese-giorno-ora-minuto-secondo.

API Java LocalDateTime

ZonedDateTime():

ZonedDateTime è una rappresentazione non modificabile di una data e ora con un fuso orario. Questa classe archivia tutti i campi di data e ora, con una precisione di nanosecondi, e un fuso orario, con un offset di zona utilizzato per gestire date e orari locali ambigui.

API Java ZonedDateTime

Calendario():

La classe Calendar è una classe astratta che fornisce metodi per la conversione tra un istante specifico nel tempo e un insieme di campi del calendario come ANNO, MESE, GIORNO_DI_MESE, ORA e così via, e per manipolare i campi del calendario, come ottenere la data della prossima settimana. Un istante nel tempo può essere rappresentato da un valore in millisecondi che è un offset dall'Epoch, 1 gennaio 1970 00:00:00.000 GMT (gregoriano).

Data():

La classe Date rappresenta un istante specifico nel tempo, con precisione al millisecondo.

Iniziamo:

Crea file: CrunchifyDateTimeCalendarTutorial.java

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);
    }
 
}

Basta eseguirlo in IntelliJ IDEA:

Uscita console.

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/ Library / Java / JavaVirtualMachines / jdk - 13.0.1.jdk / Contents / Home / bin / java - javaagent : / Applications / IntelliJ IDEA . app / Contents / lib / idea_rt . jar = 50895 : / Applications / IntelliJ IDEA . app / Contents / bin - Dfile . encoding = UTF - 8 - classpath / Users / crunchify / Documents / C / crunchify - github / CrunchifyTutorials / target / classes : / Users / crunchify / Documents / C / crunchify - github / CrunchifyTutorials / WebContent / WEB - INF / lib / zxing - 2.1.jar : / Users / crunchify / Documents / C / crunchify - github / CrunchifyTutorials / WebContent / WEB - INF / lib / commons - logging - 1.1.2.jar : / Users / crunchify / Documents / C / crunchify - github / CrunchifyTutorials / WebContent / WEB - INF / lib / commons - collections - 3.2.1.jar : / Users / crunchify / Documents / C / crunchify - github / CrunchifyTutorials / WebContent / WEB - INF / lib / javax . mail . jar : / Users / crunchify / Documents / C / crunchify - github / CrunchifyTutorials / WebContent / WEB - 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simple / json - simple / 1.1 / json - simple - 1.1.jar : / Users / crunchify / . m2 / repository / commons - net / commons - net / 2.0 / commons - net - 2.0.jar : / Users / crunchify / . m2 / repository / asm / asm / 3.3.1 / asm - 3.3.1.jar : / Users / crunchify / . m2 / repository / axis / axis / 1.4 / axis - 1.4.jar : / Users / crunchify / . m2 / repository / org / apache / axis / axis - jaxrpc / 1.4 / axis - jaxrpc - 1.4.jar : / Users / crunchify / . m2 / repository / axis / axis - wsdl4j / 1.5.1 / axis - wsdl4j - 1.5.1.jar : / Users / crunchify / . m2 / repository / commons - beanutils / commons - beanutils / 1.8.3 / commons - beanutils - 1.8.3.jar : / Users / crunchify / . m2 / repository / commons - collections / commons - collections / 3.2.1 / commons - collections - 3.2.1.jar : / Users / crunchify / . m2 / repository / commons - configuration / commons - configuration / 1.10 / commons - configuration - 1.10.jar : / Users / crunchify / . m2 / repository / commons - io / commons - 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context - 5.1.3.RELEASE.jar : / Users / crunchify / . m2 / repository / org / springframework / spring - aop / 5.1.3.RELEASE / spring - aop - 5.1.3.RELEASE.jar : / Users / crunchify / . m2 / repository / org / springframework / spring - beans / 5.1.3.RELEASE / spring - beans - 5.1.3.RELEASE.jar : / Users / crunchify / . m2 / repository / org / springframework / spring - core / 5.1.3.RELEASE / spring - core - 5.1.3.RELEASE.jar : / Users / crunchify / . m2 / repository / org / springframework / spring - jcl / 5.1.3.RELEASE / spring - jcl - 5.1.3.RELEASE.jar : / Users / crunchify / . m2 / repository / org / springframework / spring - expression / 5.1.3.RELEASE / spring - expression - 5.1.3.RELEASE.jar : / Users / crunchify / . m2 / repository / org / springframework / spring - context - support / 5.1.3.RELEASE / spring - context - support - 5.1.3.RELEASE.jar crunchify . com . tutorials . 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

Spero che questo tutorial ti aiuti a utilizzare tutte queste API di data e ora.