Hello Chris
Le 12/10/12 01:16, Mattmann, Chris A (388J) a écrit :
This makes total sense to me, and allows to take advantage of downstream
flexibility where we simply
want to standardize on interfaces like Lists and Collections.
Thanks a lot :-). Maybe the Cache class is also worth to mention (while
not yet used in SIS). This class implements the Map interface and uses
internally the java.util.concurrent package (including the
ConcurrentHashMap). It provides a mechanism for blocking a thread which
asked the value for a key when that particular value is in process of
being calculated by another thread. It also replaces automatically the
references to oldest values by weak references when the "cost" of all
entries is over a threshold. The "cost" is used-specified, but a good
example is the amount of pixels in an image. The oldest values are
replaced by weak references rather than discarded because if strong
references still exist somewhere else in the application, removing the
value from the Cache will not save anything. Quite the opposite, it
would duplicate objects if the value is recomputed.
The difference between Cache and WeakValueHashMap is that
WeakValueHashMap has no concurrency support and uses only weak
references (no mechanism replacing strong references by weak references
after some cost threshold). WeakValueHashMap is used only for avoiding
object duplications (reuse existing instances); it can't be used as a
cache since it doesn't retain entries from being garbage collected.
Regards,
Martin
