Path: csiph.com!newsfeed.hal-mli.net!feeder3.hal-mli.net!newsfeed.hal-mli.net!feeder1.hal-mli.net!eternal-september.org!feeder.eternal-september.org!mx04.eternal-september.org!.POSTED!not-for-mail
From: Joshua Cranmer <Pidgeot18@verizon.invalid>
Newsgroups: comp.lang.java.programmer
Subject: Re: trigger static init
Date: Wed, 11 Apr 2012 09:39:15 -0500
Organization: A noiseless patient Spider
Lines: 27
Message-ID: <jm452n$l9d$1@dont-email.me>
References: <5605o7di8le7conanmf0g70p1ltipeqct4@4ax.com> <m2zkalqs1m.fsf@ipa.eternal-september.org> <17423607.56.1333992983521.JavaMail.geo-discussion-forums@pbkr6> <slrnjoavkt.kvi.avl@gamma.logic.tuwien.ac.at>
Mime-Version: 1.0
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 8bit
Injection-Date: Wed, 11 Apr 2012 14:39:19 +0000 (UTC)
Injection-Info: mx04.eternal-september.org; posting-host="WpcHJSul77m+zlbR9GVqkA"; logging-data="21805"; mail-complaints-to="abuse@eternal-september.org";	posting-account="U2FsdGVkX184kpNV516s7P6sWZsKe/+icpSUF9h9A6Q="
User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:11.0) Gecko/20120327 Thunderbird/11.0.1
In-Reply-To: <slrnjoavkt.kvi.avl@gamma.logic.tuwien.ac.at>
Cancel-Lock: sha1:9pWUi2LXhW4yA/DhuMeXOZ/WnL8=
Xref: csiph.com comp.lang.java.programmer:13476

On 4/11/2012 7:52 AM, Andreas Leitgeb wrote:
> Lew<lewbloch@gmail.com>  wrote:
>> Referencing the 'class' literal does not incur class initialization.
>
> from JLS 12.4.1:
> A class [...] T is initialized immediately before first [...]
>    T is a class and an instance of T is created.
>    T is a class and a static method declared by T is invoked.
>    A static field declared by T is assigned.
>    A static field declared by T is used [ ... and not constant ... ]
>    T is a top-level class, and an assert statement (§14.10) lexically
>            nested within T is executed.
>
> Does using a class-literal<T.class>  in "synchronized(T.class) {...}" count
> in for implicitly using the monitor-field of the Class<T>-instance, or is
> it strictly undefined (or defined somewhere else)?

So, the use of "T.class" creates an object of Class<T>, which is not 
sufficient to cause T to be initialized. Some more inspection of the JLS 
(and some experiments) leads me to the conclusion that a 
synchronized(T.class) block can race with the initialization of T.

Experiments confirm that synchronized(T.class) does not cause 
initialization of T.
-- 
Beware of bugs in the above code; I have only proved it correct, not 
tried it. -- Donald E. Knuth