On 2/03/2018 12:09 PM, Xueming Shen wrote:
On 3/1/18, 4:35 PM, David Holmes wrote:
When you replace synchronized code with concurrent data structures you
introduce race conditions that are precluded in the synchronized code.
These need to be examined carefully to ensure they are safe. For
example, whenever you replace a HashMap with a ConcurrentHashMap you
need to see if put() needs to be replaced by putIfAbsent().
Hi David,
The assumption here is that putIfAbsent() does not help/save anything as
the value object
would have been created already when it reaches here. And it appears
there is no need here
to have the check&put to be atomic, replacing any existing key/value
pair is fine in this use
As long as create(len) is idempotent that should be fine.
As Claes pointed out offline you're also risking creating more than one
CHM instance. Again if create(len) is idempotent this should be harmless
but it is somewhat messy.
Also this:
195 private Map<Integer,WeakReference<CoderResult>> cache = null;
should now be volatile.
Cheers,
David
scenario. Was thinking about computIfAbsent(), but concluded it's just
little overdone (wonder
why we decided to use the WeakReference in this case, it probably is not
worth it, but keep it as
is for "compatibility" concern).
-Sherman
