#3 doesn't have the effect you think it does. Those synchronization
blocks won't have any effect.
Bob
On 4/30/05, Boehm, Hans <hans.boehm@hp.com> wrote:
> I'm giving a talk at JavaOne about finalization and the memory model.
>
> The final version of the memory model requires some explicit precaution
> to prevent the finalizers from running before ordinary methods
> complete their actions (except that constructors have special
> dispensation
> and happen before the finalizer).
>
> We failed to include any explicit recommendation or library routine
> to enforce the necessary ordering, though we discussed it extensively.
>
> There are several possible idioms that might be used to enforce that
> the correct thing happens:
>
> 1) Make all methods which might be the last ordinary call on an
> object synchronized. Make the finalizer synchronized.
>
> 2) Write to a volatile field at the end of ordinary methods,
> and read it first thing in the finalizer.
>
> 3) Put "synchronized(this){}" at the end of ordinary methods and at
> the beginning of finalizers.
>
> I originally was thinking in terms of (1) as the standard mechanism.
>
> But the more I think about it, there is no clear winner. Option (2)
> is almost certainly ugliest and fastest. Stylistically, option (3)
> looks cleanest to me, and allows more optimization than (1). If you
> want to be 100% correct, (2) and (3) may require a try ... finally to
> ensure that the synchronization operation can be executed on exceptional
> paths. (It seems REALLY unlikely that a compiler would
> optimize away the "this" pointer because it knows that a method is
> always going to generate an exception.)
>
> I think I'm inclined to go with (3) in my main example.
>
> Opinions?
>
> Hans
>
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