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Java 8 Time API - ZonedDateTime - specify the default value for ZoneId when parsing

I am trying to write a generic method to return the ZonedDateTimespecified date as Stringwell as its format.

How to make ZonedDateTimeuse of the default value ZoneIdif it is not specified in the date String?

This can be done using java.util.Calendar, but I want to use the Java 8 time API.

This question here uses a fixed time zone. I specify the format as an argument. Both the date and its format are arguments String. More general.

Code and output below:

public class DateUtil {
    /** Convert a given String to ZonedDateTime. Use default Zone in string does not have zone.  */
    public ZonedDateTime parseToZonedDateTime(String date, String dateFormat) {
        //use java.time from java 8
        DateTimeFormatter formatter = DateTimeFormatter.ofPattern(dateFormat);
        ZonedDateTime zonedDateTime = ZonedDateTime.parse(date, formatter);
        return zonedDateTime;
    }

    public static void main(String args[]) {
        DateUtil dateUtil = new DateUtil();
        System.out.println(dateUtil.parseToZonedDateTime("2017-09-14 15:00:00+0530", "yyyy-MM-dd HH:mm:ssZ"));
        System.out.println(dateUtil.parseToZonedDateTime("2017-09-14 15:00:00", "yyyy-MM-dd HH:mm:ss"));
    }
}

Output

2017-09-14T15:00+05:30
Exception in thread "main" java.time.format.DateTimeParseException: Text '2017-09-14 15:00:00' could not be parsed: Unable to obtain ZonedDateTime from TemporalAccessor: {},ISO resolved to 2017-09-14T15:00 of type java.time.format.Parsed
    at java.time.format.DateTimeFormatter.createError(DateTimeFormatter.java:1920)
    at java.time.format.DateTimeFormatter.parse(DateTimeFormatter.java:1855)
    at java.time.ZonedDateTime.parse(ZonedDateTime.java:597)
    at com.nam.sfmerchstorefhs.util.DateUtil.parseToZonedDateTime(DateUtil.java:81)
    at com.nam.sfmerchstorefhs.util.DateUtil.main(DateUtil.java:97)
Caused by: java.time.DateTimeException: Unable to obtain ZonedDateTime from TemporalAccessor: {},ISO resolved to 2017-09-14T15:00 of type java.time.format.Parsed
    at java.time.ZonedDateTime.from(ZonedDateTime.java:565)
    at java.time.format.Parsed.query(Parsed.java:226)
    at java.time.format.DateTimeFormatter.parse(DateTimeFormatter.java:1851)
    ... 3 more
Caused by: java.time.DateTimeException: Unable to obtain ZoneId from TemporalAccessor: {},ISO resolved to 2017-09-14T15:00 of type java.time.format.Parsed
    at java.time.ZoneId.from(ZoneId.java:466)
    at java.time.ZonedDateTime.from(ZonedDateTime.java:553)
    ... 5 more
+4
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6 answers

A ZonedDateTime , , . ( ).

, , ZonedDateTime, , (, , , , ).

- ZonedDateTime, , LocalDateTime :

public ZonedDateTime parseToZonedDateTime(String date, String dateFormat) {
    // use java.time from java 8
    DateTimeFormatter formatter = DateTimeFormatter.ofPattern(dateFormat);
    ZonedDateTime zonedDateTime = null;
    try {
        zonedDateTime = ZonedDateTime.parse(date, formatter);
    } catch (DateTimeException e) {
        // couldn't parse to a ZoneDateTime, try LocalDateTime
        LocalDateTime dt = LocalDateTime.parse(date, formatter);

        // convert to a timezone
        zonedDateTime = dt.atZone(ZoneId.systemDefault());
    }
    return zonedDateTime;
}

ZoneId.systemDefault(), JVM , , runtime, , .

API IANA ( Region/City, America/Sao_Paulo Europe/Berlin). 3- (, CST PST), .

( , ), ZoneId.getAvailableZoneIds().

, ZoneId.of("America/New_York") ( , ZoneId.getAvailableZoneIds(), -) ZoneId.systemDefault().

parseBest() method, ( TemporalQuery" s), :

public ZonedDateTime parseToZonedDateTime(String date, String dateFormat) {
    DateTimeFormatter formatter = DateTimeFormatter.ofPattern(dateFormat);

    // try to create a ZonedDateTime, if it fails, try LocalDateTime
    TemporalAccessor parsed = formatter.parseBest(date, ZonedDateTime::from, LocalDateTime::from);

    // if it a ZonedDateTime, return it
    if (parsed instanceof ZonedDateTime) {
        return (ZonedDateTime) parsed;
    }
    if (parsed instanceof LocalDateTime) {
        // convert LocalDateTime to JVM default timezone
        LocalDateTime dt = (LocalDateTime) parsed;
        return dt.atZone(ZoneId.systemDefault());
    }

    // if it can't be parsed, return null or throw exception?
    return null;
}

ZonedDateTime::from LocalDateTime::from, ZonedDateTime, , LocalDateTime.

, , . , ( , LocalDate, LocalTime, OffsetDateTime .., from, parseBest - TemporalQuery, , , ).

a LocalDateTime ZonedDateTime atZone() , ().

, (America/Sao_Paulo) , DST.

- DST 16 th 2016: 1 1 ( -03:00 -02:00). , 00:00 00:59 ( , 23: 59: 59.999999999 01:00). , :

ZoneId zone = ZoneId.of("America/Sao_Paulo");

// October 16th 2016 at midnight, DST started in Sao Paulo
LocalDateTime d = LocalDateTime.of(2016, 10, 16, 0, 0, 0, 0);
ZonedDateTime z = d.atZone(zone);
System.out.println(z);// adjusted to 2017-10-15T01:00-02:00[America/Sao_Paulo]

DST : 19 th 2017 1 , 23 18 th ( -02:00 -03:00). , 23:00 23:59 ( : -03:00 -02:00), , . DST, withLaterOffsetAtOverlap() DST:

// February 19th 2017 at midnight, DST ends in Sao Paulo
// local times from 23:00 to 23:59 at 18th exist twice
LocalDateTime d = LocalDateTime.of(2017, 2, 18, 23, 0, 0, 0);
// by default, it gets the offset before DST ends
ZonedDateTime beforeDST = d.atZone(zone);
System.out.println(beforeDST); // before DST end: 2018-02-17T23:00-02:00[America/Sao_Paulo]

// get the offset after DST ends
ZonedDateTime afterDST = beforeDST.withLaterOffsetAtOverlap();
System.out.println(afterDST); // after DST end: 2018-02-17T23:00-03:00[America/Sao_Paulo]

, DST (-02:00 -03:00). DST, , .

+5

java.time , - , , , , .

, Zone - LocalDateTime ZonedDateTime, , ( ).

- , , .

, , , ( , ):

TemporalAccessor parsed = f.parse(string);
if (parsed.query(TemporalQueries.zone()) == null) {
  parsed = f.withZone(ZoneId.systemDefault()).parse(string);
}
return ZonedDateTime.from(parsed);

, , , , ( , -), .

, , , :

class TemporalWithZone implements TemporalAccessor {
  private final ZoneId zone;
  private final TemporalAccessor delegate;
  public TemporalWithZone(TemporalAccessor delegate, ZoneId zone) {
    this.delegate = requireNonNull(delegate);
    this.zone = requireNonNull(zone);
  }

  <delegate methods: isSupported(TemporalField), range(TemporalField), getLong(TemporalField)>

  public <R> R query(TemporalQuery<R> query) {
    if (query == TemporalQueries.zone() || query == TemporalQueries.zoneId()) {
      return (R) zone;
    }
    return delegate.query(query);
  }
}
+3

DateTimeFormatterBuilder, OFFSET_SECOND:

EDIT: ZoneOffset ZoneRules Instant. :

class DateUtil {
  public ZonedDateTime parseToZonedDateTime(String date, String dateFormat) {
    DateTimeFormatter formatter = DateTimeFormatter.ofPattern(dateFormat);
    LocalDateTime localDateTime = LocalDateTime.parse(date, formatter);
    ZoneOffset defaultOffset =  ZoneId.systemDefault().getRules().getOffset(localDateTime);
    DateTimeFormatter dateTimeFormatter = new DateTimeFormatterBuilder()
            .append(formatter)
            .parseDefaulting(ChronoField.OFFSET_SECONDS, defaultOffset.getTotalSeconds())
            .toFormatter();
    return ZonedDateTime.parse(date, dateTimeFormatter);
  }
}

:

2017-09-14T15:00+05:30
2017-09-14T15:00+02:00
+2

Java 8 ZonedDateTime ZonedDateTime.

, try catch - , .

, , :

public class DateUtil {
     /** Convert a given String to ZonedDateTime. Use default Zone in string does not have zone.  */
    public ZonedDateTime parseToZonedDateTime(String date, String dateFormat) {
        //use java.time from java 8
        DateTimeFormatter formatter = DateTimeFormatter.ofPattern(dateFormat);
        ZonedDateTime zonedDateTime = null;
        try {
            zonedDateTime = ZonedDateTime.parse(date, formatter);
        } catch (DateTimeException e) {
            // If date doesn't contains Zone then parse with LocalDateTime 
            LocalDateTime localDateTime = LocalDateTime.parse(date, formatter);
            zonedDateTime = localDateTime.atZone(ZoneId.systemDefault());
        }
        return zonedDateTime;
    }

    public static void main(String args[]) {
        DateUtil dateUtil = new DateUtil();
        System.out.println(dateUtil.parseToZonedDateTime("2017-09-14 15:00:00+0530", "yyyy-MM-dd HH:mm:ssZ"));
        System.out.println(dateUtil.parseToZonedDateTime("2017-09-14 15:00:00", "yyyy-MM-dd HH:mm:ss"));
    }
}

http://www.codenuclear.com/java-8-date-time-intro java

+2

ZoneId withZone DateTimeFormatter:

DateTimeFormatter formatter = DateTimeFormatter.ofPattern(dateFormat).withZone("+0530");
+1

, :

formatter = DateTimeFormatter.ofPattern(dateFormat).withZone(ZONE_UTC);

Once the formatter is compiled, you can call withZone(ZoneId)to create a new formatter with the given time zone.

-1
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Source: https://habr.com/ru/post/1685672/

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