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Subject: Re: Synchronization of the constructor
Date: Sun, 14 Aug 2011 11:28:52 -0700
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On 8/14/2011 9:10 AM, Lew wrote:

> See JLS §17.5: "...It will also see versions of
> any object or array referenced by those final fields that are at
> least as up-to-date as the final fields are."
>

This is a little misleading, I think.  In fact the update does not occur 
when the final field is written ("at least as up-to-date as the final 
fields are").  The update occurs at the end of the constructor.

JLS 17.5.1:
"The semantics for final fields are as follows. Let o be an object, and 
c be a constructor for o in which f is written. A freeze action on a 
final field f of o takes place when c exits, either normally or abruptly."

The "freeze action" is a little unclear.  It's not technically a 
synchronization, because immutable objects are specifically stated to 
not use synchronization.  It is a happens-before though (even though 
that language isn't used), and it appears to imply a memory-barrier.

I'm not sure exactly why they use "freeze action" and not 
happens-before.  There might be some subtle difference for compiler 
writers, than doesn't affect the rest of us.