JEP 193: Enhanced Volatiles (original) (raw)

Doug Lea dl at cs.oswego.edu
Tue Mar 4 12:05:33 UTC 2014

On 03/04/2014 02:41 AM, Jeroen Frijters wrote:

Brian Goetz wrote:

Embedded in this proposal is the desire to not provide a full-blown "lvalue" form for variables; supporting any form of pass-by-reference at the language level is a super-non-goal here. Why is this? It solves these problems in an extremely clean way and also provides lots of other value (for example, for JEP 191: Foreign Function Interface). I understand pass-by-reference is an expensive feature, but IMNSHO poluting Java with this proposal will prove to be more expensive in the long run. It's like erased generics all over again.

The expensive version of pass-by-reference is already supported using java.lang.reflect.Field. You can think of .volatile as a version of such mechanics that only works within the context of a single expression, not across method calls. There is plenty of precedent for this. For example you cannot emulate the "+=" operator as a standalone method without resorting to reflection. You can view this JEP as an extension mechanism for safely adding similar l-value-based operators. (Although only the JDK can implement these extensions.)

-Doug

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