How to Convert a 2021-09-29T17:04:31.0000 05:30 to 2021-09-29 17:04:31.0000000 Asia/Calcutta In Java?

and additional question is here- I tried many ways to get the timezone(Asia/Calcutta) from offset( 05:30) but unable to get. Can someone please help?

CodePudding user response：

Since you cannot derive a zone from an offset (reliably), you may want to use a workaround / different approach.

Here's an example that parses the input String to an OffsetDateTime using a suitable DateTimeFormatter and then creates the desired ZoneId which it applies to the OffsetDateTime in order to create a ZonedDateTime.

public static void main(String[] args) {
    // your example input
    String offsetTime = "2021-09-29T17:04:31.0000  05:30";
    // define a formatter that parses a String of this format
    DateTimeFormatter dtf = DateTimeFormatter.ofPattern("uuuu-MM-dd'T'HH:mm:ss.SSSS xxx");
    // then parse it to an object that knows date, time and offset
    OffsetDateTime odt = OffsetDateTime.parse(offsetTime, dtf);
    // print the result
    System.out.println(odt);

    // now define the desired zone
    ZoneId asiaCalcutta = ZoneId.of("Asia/Calcutta");
    // and use the offset-aware object to apply the zone
    ZonedDateTime zdt = odt.atZoneSameInstant(asiaCalcutta);
    // print it
    System.out.println(zdt);
}

This outputs

2021-09-29T17:04:31 05:30
2021-09-29T17:04:31 05:30[Asia/Calcutta]

Please note: This will only keep the same offset if the offset and the zone actually match. I don't know your concrete requirements, so only you can know if this approach is appropriate in your situation or not.

If you want to find out time zones that currently use a specific offset and then make your code decide which is the correct one, you may want to have a look at this question and its answers.

CodePudding user response：

I tried to write this code to cover three possibilities String parameter , or LocalDateTime parameter and ZonedDateTime Parameter :

      import java.time.LocalDateTime;
      import java.time.ZoneId;
      import java.time.ZonedDateTime;
      import java.time.format.DateTimeFormatter;

      public class SpecialFormater {

   // parameter : ZonedDateTime
   public static String specialFormaterZonedDateTime(ZonedDateTime zdt) {

    DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss.SSSSSSS");
    ZoneId zid = zdt.getZone();
    System.out.println("Your initial format                ="   zdt);
    String result = "Your expected format               ="   zdt.format(formatter)   " "   zid;

    return result;
}
  // parameter : LocalDateTime
 public static String specialFormaterLocalDateTime(LocalDateTime dt) {

    DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss.SSSSSSS");

    ZoneId zid = ZoneId.of("Asia/Calcutta");

    System.out.println("Your initial format                ="   dt);
    ZonedDateTime zdt = ZonedDateTime.of(dt, zid);
    System.out.println("Your zoned dateTime default format ="   zdt);
    String result = "Your expected format               ="   dt.format(formatter)   " "   zid;

    return result;
}

// Parameter : String
public static String specialFormaterString(String localDateTime) {
    System.out.println("String before formatting   ="   localDateTime);
    String pattern = "yyyy-MM-dd'T'HH:mm:ss.SSSS xxx";
    DateTimeFormatter formatter = DateTimeFormatter.ofPattern(pattern);
    LocalDateTime dt = LocalDateTime.parse(localDateTime, formatter);
    ZoneId zid = ZoneId.of("Asia/Calcutta");

    DateTimeFormatter formatter2 = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss.SSSSSSS");
    String result = "String after  formatting   ="   dt.format(formatter2)   " "   zid;
    return result;
}

public static void main(String[] args) {
System.out.println("specialFormaterLocalDateTime");
    System.out.println(specialFormaterLocalDateTime(LocalDateTime.now()));
    System.out.println("***********");
    System.out.println();
    System.out.println("specialFormaterString");
    System.out.println(specialFormaterString("2021-09-29T17:04:31.0000  05:30"));
    System.out.println("**********");       
    System.out.println();
    System.out.println("specialFormaterZonedDateTime");
    System.out.println(specialFormaterZonedDateTime(ZonedDateTime.now()));
}
}

Output :

  specialFormaterLocalDateTime
  Your initial format                =2021-10-06T12:35:45.029
  Your zoned dateTime default format =2021-10-06T12:35:45.029 05:30[Asia/Calcutta]
  Your expected format               =2021-10-06 12:35:45.0290000 Asia/Calcutta
  ***********

  specialFormaterString
  String before formatting   =2021-09-29T17:04:31.0000  05:30
  String after  formatting   =2021-09-29 17:04:31.0000000 Asia/Calcutta
  **********

  specialFormaterZonedDateTime
  Your initial format                =2021-10-06T12:35:45.064 02:00[Europe/Paris]
  Your expected format               =2021-10-06 12:35:45.0640000 Europe/Paris