Convert java.util.TimeZone String to java.util.TimeZone

Question

Is it possible to convert a java.util.TimeZone String

sun.util.calendar.ZoneInfo[id=\"America/Los_Angeles\",offset=-28800000,dstSavings=3600000,useDaylight=true,transitions=185,lastRule=java.util.SimpleTimeZone[id=America/Los_Angeles,offset=-28800000,dstSavings=3600000,useDaylight=true,startYear=0,startMode=3,startMonth=2,startDay=8,startDayOfWeek=1,startTime=7200000,startTimeMode=0,endMode=3,endMonth=10,endDay=1,endDayOfWeek=1,endTime=7200000,endTimeMode=0]]

back to java.util.TimeZone object?

You could possibly parse the id out of this string and get a new TimeZone object from it. But it seems like an XY problem: why do you get a string like that anyway, and why can't you use the original object or a serialization of it or an easier to parse string? — RealSkeptic
– RealSkeptic, Commented Jun 29, 2017 at 7:14
I've decided to use the "id" value of the original timezone object instead of this string. Thanks! — Ezil Kannan
– Ezil Kannan, Commented Jun 29, 2017 at 8:15
FYI, TimeZone is one of the troublesome old date-time classes that are now legacy, supplanted by the java.time classes. See the classes ZoneId and ZoneOffset. — Basil Bourque
– Basil Bourque, Commented Jun 29, 2017 at 8:22
Agree with @BasilBourque. If you got the ID string (either from parsing or some other way), use ZoneId.of(idString). Still easier if you got the original TimeZone object: timeZoneObject.toZoneId(). — Anonymous
– Anonymous, Commented Jun 29, 2017 at 12:45

D. Kovács · Accepted Answer · 2017-06-29 07:54:33Z

1

Part of Effective Java; Item 10:

Provide programmatic information to all the information provided by toString, or clients may try to parse the string to retrieve it.

In other words: if it is doable, don't try to parse the output of toString. If you are forced to do it (but only if really-really-really there is no other way), then you could do it:

you have to do it with reflection (TimeZone is an abstract class, in the toString output you see that this instance is not a ZoneInfo but a SimpleTimeZone)
you have to parse the data which you need in any of the applicable constructors and invoke it

There is no "easy solution" to "backmapping" a toString representation of TimeZone into a TimeZone object. (There are some APIs where you have a fromString method or similar, the new Java Date API is not one of them, and it shouldn't be).

answered Jun 29, 2017 at 7:54

D. Kovács

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1 Comment

Ezil Kannan Over a year ago

I will stick to using the original TimeZone object instead of this String. This seems to add unnecessary complexity. Thank you.

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