I am trying to create an instance of Instant from date and time strings. Date is formatted like this yyyy-MM-dd. So the values could look like this:

val date = "2021-11-25"
val time = "15:20"

I am trying to make a valid instant from this 2 strings like this:

val dateTime = "${date}T${time}:00"
val instantDateTime = ZonedDateTime.parse(dateTime, 
                                          DateTimeFormatter.ISO_OFFSET_DATE_TIME.withZone(defaultTimeZone)
                                         ).toInstant()

I have also tried with it:

val instantDateTime = Instant.from(DateTimeFormatter .ISO_OFFSET_DATE_TIME.withZone(defaultTimeZone).parse(dateTime))

But, that is not working, I get:

Exception in thread "main" java.time.format.DateTimeParseException: Text '2021-11-25T15:20:00' could not be parsed at index 19

CodePudding user response：

You can combine the date and time strings to create a date-time string in ISO 8601 format which you can parse into LocalDateTime and then convert into Instant by using the applicable ZoneId. Note that the modern Date-Time API is based on ISO 8601 and does not require using a DateTimeFormatter object explicitly as long as the Date-Time string conforms to the ISO 8601 standards.

import java.time.Instant;
import java.time.LocalDateTime;
import java.time.ZoneId;

public class Main {
    public static void main(String[] args) {
        String strDate = "2021-11-25";
        String strTime = "15:20";
        String strDateTime = strDate   "T"   strTime;
        LocalDateTime ldt = LocalDateTime.parse(strDateTime);
        Instant instant = ldt.atZone(ZoneId.systemDefault()).toInstant();
        System.out.println(instant);
    }
}

Output:

2021-11-25T15:20:00Z

ONLINE DEMO

An alternative way to create the instance of LocalDateTime can be as suggested by daniu i.e. parse the date and time strings individually and create the instance of LocalDateTime using them.

Demo:

import java.time.Instant;
import java.time.LocalDate;
import java.time.LocalDateTime;
import java.time.LocalTime;
import java.time.ZoneId;

public class Main {
    public static void main(String[] args) {
        String strDate = "2021-11-25";
        String strTime = "15:20";
        LocalDateTime ldt = LocalDateTime.of(LocalDate.parse(strDate), LocalTime.parse(strTime));
        Instant instant = ldt.atZone(ZoneId.systemDefault()).toInstant();
        System.out.println(instant);
    }
}

ONLINE DEMO

Learn more about the modern Date-Time API^* from Trail: Date Time. Check this answer and this answer to learn how to use java.time API with JDBC.

^{* If you are working for an Android project and your Android API level is still not compliant with Java-8, check Java 8 APIs available through desugaring. Note that Android 8.0 Oreo already provides support for java.time.}

CodePudding user response：

Your date string doesn't include a timezone, so it cannot be parsed directly to a ZonedDateTime (see javadoc for ZonedDateTime#parse).

Try parsing the string to a LocalDateTime instead (using LocalDate#parse).

You can then convert the the LocalDateTimeto an Instant using LocalDateTime#toInstant or to a ZonedDateTime using LocalDateTime#atZone