RFR(m): 8139233 add initial compact immutable collection implementations

[Stuart Marks]

On 5/5/16 2:22 PM, Eddie Aftandilian wrote:
> FWIW, at Google we have a patch against our JDK that randomizes hash iteration
> order.  For test execution we randomize with a unique seed per JVM invocation.
> For production we force a specific seed for all executions.  This approach
> catches most issues during automated testing, but reduces the likelihood of an
> issue in production.

Yes, I've heard of such a thing.

 From what I understand, this randomizes the iteration order of the *existing* 
collections like HashMap. It makes sense for this to be an opt-in feature for 
existing collections, since it seems pretty unwise to expose a behavioral change 
to large quantities of existing code. Unfortunately, from time to time the JDK 
does change the iteration order of the existing collections, and unsurprisingly, 
lots of things break.

It would be interesting to see such a patch proposed for OpenJDK. It'd be good 
to enable it during test runs, for a start.

s'marks