RFD: Replace class java.lang.Shutdown.Lock with Object?

[Roger Riggs]

Hi,

String is also an Identity class  and its value could distinguish 
between the cases. (Both strings can be very short).

About java.lang.Object as a lock, the pervasiveness of `new Object()` 
for locks resulted in giving it special dispensation in as a supertype 
of value objects. Trying to change its existing uses was determined to 
be infeasible.

Regards, Roger


On 1/25/26 11:17 AM, Chen Liang wrote:
> Checked this and noted this Lock is used by both lock and shutdownLock 
> - this makes the Lock class less informative to me.
> Maybe we should replace one of the locks with Object, or add a new 
> class to distinguish these two locks?
>
> Confidential- Oracle Internal
>
> ------------------------------------------------------------------------
> *From:* core-libs-dev <core-libs-dev-retn at openjdk.org> on behalf of 
> Eirik Bjørsnøs <eirbjo at gmail.com>
> *Sent:* Wednesday, January 21, 2026 12:28 AM
> *To:* David Holmes <david.holmes at oracle.com>
> *Cc:* core-libs-dev at openjdk.org <core-libs-dev at openjdk.org>
> *Subject:* Re: RFD: Replace class java.lang.Shutdown.Lock with Object?
> On Wed, Jan 21, 2026 at 6:38 AM David Holmes <david.holmes at oracle.com> 
> wrote:
>
>     No I suppose not. Though I'm not sure trimming the class will make
>     any
>     observable/practical difference in the normal case.
>
>
> Thanks! I agree trimming these two classes (of ~428 loaded at startup) 
> alone has limited value. But there are other berries to pick and 
> the cumulative impact may have an observable effect on startup. Two 
> berries feed no one, with a handful we can make a delicious jam :)
>
>     So effectively this is like declaring a single global class that all
>     "new Object()'s" would be instances of.
>
>     So using new Object() will not be a problem.
>
>
> Thanks for the Valhalla reference, interesting to see how "new 
> Object()" can be redefined like this.
>
> Eirik.
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