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From: Knute Johnson <nospam@knutejohnson.com>
Newsgroups: comp.lang.java.programmer
Subject: Re: Volatile happens before question
Date: Tue, 17 Jan 2012 20:01:08 -0800
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On 1/17/2012 4:14 PM, markspace wrote:
> On 1/17/2012 3:46 PM, Knute Johnson wrote:
>
>> And to quote Goetz "When a field is declared volatile, the compiler and
>> runtime are put on notice that this variable is shared and that
>> operations on it should not be reordered with other memory operations."
>
>
> To get that behavior, you have to actually read from the volatile after
> writing to it. Check the JLS. Both threads must participate in the
> happens-before operation, or this *is no* happens-before behavior.

Assigning a value to a is a write.  Using it in the if test is a read.

-- 

Knute Johnson