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https://issues.apache.org/jira/browse/LANG-367?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12538986
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Paul Benedict commented on LANG-367:
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Based on this link:
http://www.ibm.com/developerworks/java/library/j-jtp09263.html
"In any case, it's better to be clear in the documentation about how a class
behaves when an instance is shared across threads. As an example of this
pitfall, the class java.text.SimpleDateFormat is not thread-safe, but it wasn't
until the 1.4 JDK that this was documented in the Javadoc. How many developers
mistakenly created a static instance of SimpleDateFormat and used it from
multiple threads, unaware that their programs were not going to behave
correctly under heavy load? Don't do this to your customers or colleagues!"
> FastDateFormat thread safety
> ----------------------------
>
> Key: LANG-367
> URL: https://issues.apache.org/jira/browse/LANG-367
> Project: Commons Lang
> Issue Type: Bug
> Reporter: Sebb
> Fix For: 2.4
>
> Attachments: FastDateFormat.patch
>
>
> FastDateFormat has several static HashMaps. These are currently not final, so
> there is no guarantee that they will be visible to all threads.
> Patch to follow.
> Also, as far as I can make out, the class shares SimpleDateFormat instances
> between threads.
> It does not document why this is OK.
> I'm guessing that it assumes that instances of the SimpleDateFormat class are
> thread-safe provided that they have the same attributes, but this is not
> documented. If this is the case, it's not clear that it is a valid assumption.
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