How to list the timezone offset, timezone ID, and long name in Joda Time / Java 8?

Question

Time zone ids of Joda Time can simply be displayed with the following segment of code.

Set<String> zoneIds = DateTimeZone.getAvailableIDs();

for(String zoneId:zoneIds) {
    System.out.println(zoneId);
}

But how to display the corresponding timezone offset, timezone ID, and long name so that the list could look something like the following?

(GMT-10:00) Pacific/Honolulu, Hawaii Standard Time
(GMT-10:00) Pacific/Johnston, Hawaii Standard Time
(GMT-10:00) Pacific/Fakaofo, Tokelau Time
(GMT-10:00) HST, Hawaii Standard Time

They are needed to list in a drop-down-box for selection.

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The following snippet shows the names but the offset it displays looks wonky.

Set<String> zoneIds = DateTimeZone.getAvailableIDs();

for (String zoneId : zoneIds) {
    int offset = DateTimeZone.forID(zoneId).getOffset(new DateTime());
    String longName = TimeZone.getTimeZone(zoneId).getDisplayName();

    System.out.println("(" + offset + ") " + zoneId + ", " + longName);
}

Out of the long list it displays, a few of them are shown like,

(-36000000) Pacific/Honolulu, Hawaii Standard Time
(-36000000) Pacific/Johnston, Hawaii Standard Time
(-36000000) Pacific/Fakaofo, Tokelau Time
(-36000000) HST, Hawaii Standard Time

The offset should be as shown in this list.

Answer 1

The following approach worked.

import java.util.Set;
import java.util.TimeZone;
import org.joda.time.DateTimeZone;
import org.joda.time.format.DateTimeFormat;
import org.joda.time.format.DateTimeFormatter;

Set<String> zoneIds = DateTimeZone.getAvailableIDs();
DateTimeFormatter dateTimeFormatter = DateTimeFormat.forPattern("ZZ");

for (String zoneId : zoneIds) {
    String offset = dateTimeFormatter.withZone(DateTimeZone.forID(zoneId)).print(0);
    String longName = TimeZone.getTimeZone(zoneId).getDisplayName();

    System.out.println("(" + offset + ") " + zoneId + ", " + longName);
}

There could also be other and probably better ways that I'm right now unaware of.

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Or

import java.util.Set;
import org.joda.time.DateTimeUtils;
import org.joda.time.DateTimeZone;
import org.joda.time.format.DateTimeFormat;
import org.joda.time.format.DateTimeFormatter;

Set<String> zoneIds = DateTimeZone.getAvailableIDs();
DateTimeFormatter dateTimeFormatter = DateTimeFormat.forPattern("ZZ");

for (String zoneId : zoneIds) {
    String offset = dateTimeFormatter.withZone(DateTimeZone.forID(zoneId)).print(0);
    String longName = DateTimeZone.forID(zoneId).getName(DateTimeUtils.currentTimeMillis());

    System.out.println("(" + offset + ") " + zoneId + ", " + longName);
}

For Greenwich Mean Time (Etc/GMT+0, for example), it would display, for example +00:00 instead of displaying GMT+00:00 as in the first case.

If the name is not available for the locale, then this method (public final String getName(long instant)) returns a string in the format [+-]hh:mm.

An appropriate Locale can also be used, if needed using the overloaded method,

public String getName(long instant, Locale locale)

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Short names, for example UTC for Coordinated Universal Time can be displayed as follows.

import java.util.Set;
import org.joda.time.DateTimeUtils;
import org.joda.time.DateTimeZone;
import org.joda.time.format.DateTimeFormat;
import org.joda.time.format.DateTimeFormatter;

Set<String> zoneIds = DateTimeZone.getAvailableIDs();
DateTimeFormatter dateTimeFormatter = DateTimeFormat.forPattern("ZZ");

for (String zoneId : zoneIds) {
    String offset = dateTimeFormatter.withZone(DateTimeZone.forID(zoneId)).print(0);
    String shortName = DateTimeZone.forID(zoneId).getShortName(DateTimeUtils.currentTimeMillis());

    System.out.println("(" + offset + ") " + zoneId + ", " + shortName);
}

With an appropriate Locale, if needed using the overloaded method,

public String getShortName(long instant, Locale locale)

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Update :

Using the Java Time API in Java SE 8 in which this is further simplified.

import java.time.ZoneId;
import java.time.ZoneOffset;
import java.time.ZonedDateTime;
import java.time.format.TextStyle;
import java.util.Locale;
import java.util.Set;

Set<String> zoneIds = ZoneId.getAvailableZoneIds();

for (String zoneId : zoneIds) {
    ZoneId zone = ZoneId.of(zoneId);
    ZonedDateTime zonedDateTime = ZonedDateTime.now(zone);

    ZoneOffset offset = zonedDateTime.getOffset();
    String longName = zone.getDisplayName(TextStyle.FULL, Locale.ENGLISH);

    System.out.println("(" + offset + ") " + zoneId + ", " + longName);
}

The display name has various styles available in java.time.format.TextStyle. For example, abbreviations can be displayed using TextStyle.SHORT.

zone.getDisplayName(TextStyle.FULL, Locale.ENGLISH) will display long names like "India Time". This is however, not a full name unlike Joda Time.

The following will display a full name of the given name like "India Standard Time" (wherever applicable).

DateTimeFormatter pattern = DateTimeFormatter.ofPattern("zzzz");
String longName = pattern.format(ZonedDateTime.now(ZoneId.of(zoneId)));

The following will display a zone-offset of the given zone like GMT+05:30 (note the capitalization of the pattern).

DateTimeFormatter pattern = DateTimeFormatter.ofPattern("ZZZZ");
String longName = pattern.format(ZonedDateTime.now(ZoneId.of(zoneId)));

The following is for displaying abbreviations.

DateTimeFormatter pattern = DateTimeFormatter.ofPattern("zzz");
String longName = pattern.format(ZonedDateTime.now(ZoneId.of(zoneId)));

Capital ZZZ for zone-offset like +0530, +0000.

https://docs.oracle.com/javase/8/docs/api/java/time/format/DateTimeFormatter.html