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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 08:49:14 -0800
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On 1/17/2012 8:33 AM, markspace wrote:
> On 1/17/2012 8:18 AM, Knute Johnson wrote:
>
>>> Does this work in reverse too?
>>>
>>> For example,
>>>
>>> Thread 1
>>> int b = 0;
>>> volatile boolean a = false;
>>> ...
>>> ...
>>> a = true;
>>> b = 1;
>>>
>>> Thread 2
>>> int bStore = b;
>>> if (!a) {
>>> System.out.println("The value of b is " + bStore);
>>> }
>>>
>>> Will this always print either "The value of b is 0" or nothing.
>>
>> Yes
>
>
> I'm pretty sure Peter got the correct answer which is "no." I want to
> stick my answers in a separate reply, so I'll just add that this is an
> easy mistake to make and if both Peter and you hadn't already provided
> some insights I probably would have flubbed it up myself.
>
> Reasoning about synchronization can be pretty hard. Make sure you
> consider carefully all possibilities when analyzing multi-threaded
> programs for bugs.

OK, I'll bite, if a is false how can b be anything but 0?

-- 

Knute Johnson