WeakReference with null referent
emcmanus at google.com
Tue Jul 10 23:04:54 UTC 2018
> Do you know any other example?
Here's an example from the JDK itself:
On Tue, 10 Jul 2018 at 10:11, mandy chung <mandy.chung at oracle.com> wrote:
> On 7/9/18 11:59 PM, Peter Levart wrote:
> > There are situations where being able to create a XxxReference without a
> > referent is useful. For example, imagine a doubly-linked list of
> > WeakReference subclasses - a special instance without a referent can be
> > used as the head of such list that never goes away and simplifies
> > insertion/deletion logic, etc...
> > JDK's java.lang.ref.Cleaner API uses such scheme in its implementation
> > (see jdk.internal.ref.CleanerImpl.[Phantom|Weak|Soft]CleanableRef no-arg
> > constructors).
> Thanks for pointing this out. It's used as a convenience and it's
> not hard to handle insertion/deletion logic though. Another
> alternative may be to create an object as the strongly reachable
> referent. I wonder if any existing code depends on null referent
> like the cleaner case and the compatibility risk. Do you know
> any other example?
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