On Fri, Jul 12, 2013 at 8:05 AM, roger riggs <roger.ri...@oracle.com> wrote:
> I don't see a functional issue with this;
>
You need to study the Java memory model then.
> The DateTimeFormatter created by each thread will have exactly the same
> behavior and semantics.
> The caller gets an instance that preforms as required.
>
No, that's not guaranteed with the current code.
>
> dt is just a cache to improve performance.
>
> The only condition at risk is the two calls to dateTime() do not return
> the same (==) instance.
>
No, the risk is that a second concurrent thread gets a reference to the not
yet completed object, which can cause unpredictable behavior.
>
> From the callers point of view what other observable behavior might be
> different?
>
It's a possible race condition and the memory model allows re-ordering of
operations, so anything could go wrong, from an Exception to plain wrong
formatting.
>
> Roger
>
>
>
> On 7/12/2013 5:27 AM, Stephen Colebourne wrote:
> > You may be right, although neither volatile nor synchronized are
> appealing here.
> > Please raise an issue on GitHub
> > Stephen
> >
> > On 12 July 2013 10:19, Lin Wang <superno...@gmail.com> wrote:
> >> The javadoc of ISODateTimeFormat class says it's thread-safe and
> immutable.
> >> The static fields are lazily initialized. However it seems it's not
> done in
> >> a thread-safe manner.
> >>
> >> For example, dt is lazily initialized in
> >> public static DateTimeFormatter dateTime() {
> >> if (dt == null) {
> >> dt = new DateTimeFormatterBuilder()
> >> .append(date())
> >> .append(tTime())
> >> .toFormatter();
> >> }
> >> return dt;
> >> }
> >>
> >> When there are two threads both inside this method, is it possible that
> one
> >> thread sees an unsafely published non-null dt value due to cache
> >> incoherence?
> >>
> >> Did I miss something?
> >>
> >>
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