Static fields in specialized classes

Brian Goetz brian.goetz at
Mon Oct 13 18:46:26 UTC 2014

>> Regardless of whether our implementation is by specialization or
>> erasure (or both), logically there is just *one* field 'x' for any
>> instantiation Foo<T>.
> How sure are you that this is true?  What if the type of static final
> x happens to be “T”? (nonsensical when erased, but not when reified)

Currently the rules still prohibit T to appear in member signatures, so 
that's currently a non-issue, but there are potential surprising 
behaviors in either direction, and the question is which interpretation 
is less surprising.

Consider this:

class Foo<any T> {
     static int fooCount;

     public void foo() {

Based on how generics have worked since 2004, users will expect that 
there is one fooCount field that is incremented each time foo() is 
called on any instance of a Foo<T>.  Having only some Foo<T> instances 
participate in this game, but not others, would be surprising.

Stepping back, statics are the root of much evil in Java in the first 
place.  So, while one could build a more generalized notion of statics 
in the context of reified generics as you suggest, I'm inclined to 
politely decline that option.

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