Expose elementType of EnumSet and EnumMap

Marcin Wiśnicki mwisnicki at gmail.com
Sat Sep 21 21:32:45 UTC 2013

On Sat, Sep 21, 2013 at 10:21 PM, Remi Forax <forax at univ-mlv.fr> wrote:
> No, you can add methods to one value of an enum using the anonymous class
> syntax.

Thanks for pointing this out. This is something that can be clarified
in javadoc.
Though javadocs of existing factory methods of EnumSet are not so
pedantic about "elementType" argument.

> elementType and the reified type are the same information.
> by the way, elementType and the class of the array (universe) are also the
> same information.

I fail to see a problem here. In fact this is a good case why such
method is necessary - if generics get reified in Java 9 and designers
of EnumSet decide to remove redundant elementType field, all software
depending on existence of this field will break. If on the other hand
there was a getElementType() method in Java 8, it could be safely
changed to obtain element type through whatever new mechanism is
available and existing software using getElementType() keeps working

> I've taken a look to the code, it can be changed to avoid to use
> getElementType(),
> the parameterized type is not propagated when deserializing.
> see the comment here:
> https://github.com/FasterXML/jackson-databind/blob/master/src/main/java/com/fasterxml/jackson/databind/jsontype/impl/ClassNameIdResolver.java#L49

That was just an example, there is more code like that out there,
including my own and it's not always easy to restructure it in a way
that would allow propagating declared type.

>> 2. A Visual editor of some sort may display EnumSet as a list of
>> checkboxes if it knows what type of enum values can be contained
>> within this set.
> again the declared type can be propagated.

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