JDK 12 RFR of JDK-8146726 : Refactor AbstractProcessor to use Set.of and related methods

joe darcy joe.darcy at oracle.com
Thu Nov 29 02:09:32 UTC 2018

Hi Ron,

Adding Stuart for a collections consult; Stuart, what is the currently 
recommended idiom to construct a unmodifiable collection with the same 
elements as a existing collection? In particular, for a set of Strings 
is something like

     Set.of(stringSet(new String[0]))

preferred over


Assume serialization is not a concern.

On 11/27/2018 1:23 PM, Ron Shapiro wrote:
> Set.of() throws if there are duplicate elements - but arrayToSet() 
> didn't do so. Is it intended to throw if either of these take duplicates?

Good catch.

After some pondering, I think it is preferable for AbstractProcessor to 
not treat duplicates as an error, but to issue a warning in if 
duplicates are found. Arguably, it would have been reasonable to treat 
such condition as an error initially when the API was introduced, but 
adding such a check now could have some unnecessary behavioral 
compatibility impact. The case to add an erroneous check for options is 
stronger than for supported annotations because supported annotations 
have some additional processing if modules are not present. In more 
detail, with modules to fully specify an annotation type, the module 
name needs to be used: "mod1/foo.bar" vs "mod2/foo.bar". If such a 
processor is run when modules are not used, then the names are stripped 
to "foo.bar" in both cases and that should not be treated as an error.

Revised webrev:


Will possibly update based on guidance from Stuart on the collections 
usage question.



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