RFR: Small cleanups in java.lang.ref

[mark.reinhold at oracle.com]

2018/5/18 3:11:25 -0700, per.liden at oracle.com:
> On 05/17/2018 10:03 PM, mark.reinhold at oracle.com wrote:
>> 2018/5/16 18:31:15 -0700, martinrb at google.com:
>>> I've been confused by NULL vs null for years.
>> 
>> That’s because `NULL` in ReferenceQueue.java refers to the singleton
>> object `ReferenceQueue.NULL`, not the null value.  See the long comment
>> at the top of Reference.java for an explanation.
>> 
>> To improve this you could change mentions of `NULL` in the comments to
>> `ReferenceQueue.NULL`, but changing them to `null` would be incorrect.
> 
> The comments that were changed in the proposed patch refer to the 
> Reference.next and Reference.discovered fields, not Reference.queue. So 
> "null" should be correct there.

Oops, you’re right!  Confused by my own twenty-year old code ...

What’s missing here is a similar comment on the `Reference.queue` field.
Suggested text:

    /* When active: queue with which this reference is registered
     *     pending: queue with which this reference is registered
     *    enqueued: ReferenceQueue.ENQUEUED
     *    inactive: ReferenceQueue.NULL
     */

Martin -- while you’re at it, please lowercase “Enqueued:” and
“Inactive:” in the other comments, and hard-wrap the comment on
the `discovered` field to 80 columns.

- Mark


>>> 8203327: Small cleanups in java.lang.ref
>>> http://cr.openjdk.java.net/~martin/webrevs/jdk/Reference-cleanup/
>>> https://bugs.openjdk.java.net/browse/JDK-8203327