How can i convert time zone string to the TimeZone Object in java?

Question

I have several time zone strings in UTC format, such as `"UTC+08:00", "UTC-05:00"`, the question is how can i convert these utc format strings to the `java.util.TimeZone` in Java? I have tried to convert by `ZoneId` as follows, but it did not work: ``` ZoneId zoneId = ZoneId.of("UTC+08:00"); TimeZone timeZone = TimeZone.getTimeZone(zoneId); ``` I know `TimeZone timeZone = TimeZone.getTimeZone("Asia/Shanghai");` would work, but I do not know the mapping between `"UTC+08:00"` and `"Asia/Shanghai"`

Accepted Answer

tl;dr

- Do not use `TimeZone` class (now legacy).

- Use `ZoneOffset` and `ZoneId` instead.

Example:

```
ZoneOffset.of( "+08:00" )
```

Use `java.time.ZoneId`, not `TimeZone`

The troublesome old date-time classes bundled with the earliest versions of Java are now legacy, supplanted by the java.time classes. Among these old legacy classes is `TimeZone`, now supplanted by `ZoneId` and `ZoneOffset`.

An offset-from-UTC is a number of hours and minutes adjustment ahead of, or behind, UTC. This is represented by the `ZoneOffset` class.

A time zone is a collection of offsets, the history of changes in the offset used by a particular region in determining their wall-clock time. This is represented by the `ZoneId` class.

Using a time zone is always preferable to an offset as a zone has the offset plus so much more information. But your examples are only mere offsets. So use the `ZoneOffset` to parse the strings after deleting the characters `UTC`.

```
String input = "UTC+08:00".replace( "UTC" , "" ) ;
ZoneOffset offset = ZoneOffset.of( input ) ;
```

Do not guess the time zone

You cannot assume that a particular offset implies a particular time zone. Many zones may have used a particular offset in the past, present, or future. So you should not guess the zone.

Take, for example, the offset of `+08:00`. That offset is currently used by several different time zones including `Asia/Shangai`, `Asia/Macao`, and `Australia/Perth`.

If you are certain a particular zone was intended for a date-time value, apply it to get a `ZonedDateTime`. But do not guess.

The `Instant` class represents a moment on the timeline in UTC with a resolution of nanoseconds.

```
Instant instant = Instant.now() ;
ZoneId z = ZoneId.of( "Asia/Shanghai" ) ; 
ZonedDateTime zdt = instant.atZone( z ) ;
```

If you do not know for certain the intended time zone and have only an offset, use the offset to get an `OffsetDateTime`.

```
Instant instant = Instant.now() ;
ZoneOffset offset = ZoneOffset.of( "+08:00" ) ; 
OffsetDateTime odt = instant.atOffset( offset ) ;
```

Convert

Best to avoid the old legacy class `TimeZone`. But if you must use that class to work with old code not yet updated for the java.time classes, you can convert to/from a `ZoneId`. Use the new conversion methods added to the old classes.

```
TimeZone myLegacyTimeZone = TimeZone.getTimeZone( myModernZoneId ); 
```

…and…

```
ZoneId z = myLegacyTimeZone.toZoneId() ;
```

Note that `ZoneOffset` is a subclass of `ZoneId`. Normally, we ignore that inheritance relationship. If you have only a mere offset such as `+08:00`, use `ZoneOffset`. If you have a full time zone such as `Asia/Shanghai`, use `ZoneId`. One exception to this rule is for this conversion to/from `TimeZone` where only the superclass `ZoneId` is recognized.

How can i convert time zone string to the TimeZone Object in java?

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