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Date: Fri, 9 Mar 2012 16:44:57 +0000 (UTC)
From: "Emmanuel Bourg (Commented) (JIRA)" <jira@apache.org>
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Subject: [jira] [Commented] (SANDBOX-408) CSVFormat describes itself as
 immutable, but it is not - in particular it is not thread-safe
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    [ https://issues.apache.org/jira/browse/SANDBOX-408?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13226187#comment-13226187 ] 

Emmanuel Bourg commented on SANDBOX-408:
----------------------------------------

After checking the JLS and the excellent Java Concurrency In Practice I now understand why my analysis is wrong. CSVFormat is "effectively immutable" but must be safely published to avoid visibility issues.

I made the fields volatile to ensure the thread safety. I prefer this to the constructor idiom which is less readable with a large number of fields. Also I expect some fields to be added or removed in the near future, the clone construct will be easier to maintain. I don't mind switching to constructors later when the API is stabilized.

Thank you for pointing to this issue Sebb, that was very instructing.

                
> CSVFormat describes itself as immutable, but it is not - in particular it is not thread-safe
> --------------------------------------------------------------------------------------------
>
>                 Key: SANDBOX-408
>                 URL: https://issues.apache.org/jira/browse/SANDBOX-408
>             Project: Commons Sandbox
>          Issue Type: Bug
>          Components: CSV
>            Reporter: Sebb
>         Attachments: CSVFormat.java
>
>
> CSVFormat describes itself as immutable, but it is not @Immutable - the class fields are all mutable.
> The methods that change the fields do so by creating a clone, and returning the changed clone.
> So in a sense the class is immutable.
> However, the normal expectation is that @Immutable classes are @ThreadSafe.
> CSVFormat is not thread-safe, because the fields are not volatile, and the fields are not written & read using a common lock.
> The comment needs to be clarified or removed.

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