Is there any function in joda.time which validates a string whether it represents correct time zone or not and throws a exception if it is not in the correct format?
I am aware of TimeZone.getAvalibaleIDs() but just curious to know if there is any predefined function.
DateTimeZone.forID() will throw an exception if the ID isn't recognized.
That's appropriate if you're trying to get the actual zone - if you're just trying to validate whether an ID is valid or not, I'd use getAvailableIDs():
boolean valid = DateTimeZone.getAvailableIDs().contains(id);
That's better in terms of avoiding using exceptions for flow control, IMO. However, they're not equivalent - fixed-offset time zone IDs are valid in DateTimeZone.forID(), but may not be included in the set of available IDs.
java.util.TimeZone has a bunch of "features" that leave a bit to be desired. You should find the appropriate time zone ID for what you want, e.g. America/Los_Angeles. (But not necessarily that one...)Quoted below is a notice from the home page of Joda-Time:
Note that from Java SE 8 onwards, users are asked to migrate to java.time (JSR-310) - a core part of the JDK which replaces this project.
Solution using java.time, the modern Date-Time API: Process ZoneId.of under try/catch and catch the exception for the invalid timezone ID.
Demo:
import java.time.ZoneId;
import java.time.zone.ZoneRulesException;
import java.util.stream.Stream;
public class Main {
public static void main(String[] args) {
Stream.of(
"America/New_York",
"GMT",
"UTC",
"UCT",
"GMT+01:00",
"UTC+01:00",
"ABC"
).forEach(s -> {
try {
System.out.println(ZoneId.of(s));
} catch (ZoneRulesException e) {
System.out.println(e.getMessage());
}
});
}
}
Output:
America/New_York
GMT
UTC
UCT
GMT+01:00
UTC+01:00
Unknown time-zone ID: ABC
I do not recommend ZoneId.getAvailableZoneIds().contains(time-zone-id) because it may fail for some cases as shown below:
import java.time.ZoneId;
import java.util.Arrays;
import java.util.Set;
public class Main {
public static void main(String[] args) {
String[] arr = { "America/New_York", "GMT", "UTC", "UCT", "GMT+01:00", "UTC+01:00", "ABC" };
// Alternatively
Set<String> allZones = ZoneId.getAvailableZoneIds();
Arrays.stream(arr).forEach(s -> System.out.println(allZones.contains(s) ? s : ("Unknown time-zone ID: " + s)));
}
}
Output:
America/New_York
GMT
UTC
UCT
Unknown time-zone ID: GMT+01:00
Unknown time-zone ID: UTC+01:00
Unknown time-zone ID: ABC
Learn more about the modern Date-Time API from Trail: Date Time.
* For any reason, if you have to stick to Java 6 or Java 7, you can use ThreeTen-Backport which backports most of the java.time functionality to Java 6 & 7. 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 and How to use ThreeTenABP in Android Project.
You can write a piece of function like below instead of using Joda:
private boolean isTimeZoneValid(String givenTimeZone) {
Set timeZoneSet = new HashSet(Arrays.asList(TimeZone.getAvailableIDs()));
return timeZoneSet.contains(givenTimeZone);
}
