JDK 9 RFR of JDK-8035279: Clean up internal deprecations in BigInteger

[Peter Levart]

On 02/25/2014 09:38 PM, Brian Burkhalter wrote:
> On Feb 20, 2014, at 1:42 AM, Paul Sandoz wrote:
>
>> Not sure the static powerCache field, in the original code, needs to be volatile either:
>>
>> 1137     private static volatile BigInteger[][] powerCache;
> Is there consensus on whether "volatile" is necessary here?

I think it has to be volatile. The powerCache implementation was added 
in the following changeset:

     http://hg.openjdk.java.net/jdk9/dev/jdk/rev/7546

...and improved later in the following:

     http://hg.openjdk.java.net/jdk9/dev/jdk/rev/7586

It uses a copy-on-write technique to extend the cache with new values 
when needed. volatile is mandatory here to safely publish the newly 
constructed array-of-arrays and the newly constructed sub-array to other 
threads. Without volatile, other threads could see null slots where 
BigInteger[] and/or BigInteger objects should be...

Regards, Peter

>
> Thanks,
>
> Brian