On 09/21/2013 11:32 PM, Marcin Wiśnicki wrote:
On Sat, Sep 21, 2013 at 10:21 PM, Remi Forax <fo...@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
correctly.
There is a lot of code that cast to T or to EnumSet<T> that will start
to fail at runtime if generics are reified. One possible way to avoid
that is to create a new collection API, another is to try to reuse
existing implementations with an opt-in mecanism. In the later case, the
same class will be seen refiied
or not depending on how the collection is created, so enabling
reification will be done incrementally in that case.
getElementType is a way to export a refied type, it will add burden to
mixed mode implementation.
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.
You have to propagate declared types otherwise your code is not typesafe.
If you don't propagate type that you can de-serialize a List of String
without checking that the elements inside the List are String.
Rémi
