RFR: 8256167: Convert JDK use of `Reference::get` to `Reference::refersTo`

[Peter Levart]

On Fri, 4 Dec 2020 20:09:01 GMT, Mandy Chung <mchung at openjdk.org> wrote:

>> src/java.base/share/classes/java/util/WeakHashMap.java line 293:
>> 
>>> 291:         // then checks for equality
>>> 292:         Object k = e.get();
>>> 293:         return key == k || key.equals(k);
>> 
>> I think `key == k` is already covered by refersTo. But k could be null; checking for that here might be useful, to skip the call to equals in that case.
>
> Good point on checking k != null. A cleaner check:
> 
>         // then check for equality if the referent is not cleared
>         Object k = e.get();
>         return k != null || key.equals(k);

You meant: `return k != null && key.equals(k);` right?

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PR: https://git.openjdk.java.net/jdk/pull/1609