On Sun, 28 Nov 2010 00:09:40 -0800, Mike Schilling wrote:
Without going into all the details, I have the following situation:
There are a set of objects RTS, all of the same type, that gather
run-time statistics about the running of a program. Various related
objects with different lifecycles pass them around and use them. I'm
interested in when each member of RTS is no longer being updated,
because I want to collect its final statistics , but there's no good
way to tell when it's no longer in use except via its collection, so
when it's created I attach a weak reference to it and associate the
weak reference with a queue. When the reference is delivered, I
record the statistics. [1]
So far so good. The question is, what's the best way to keep the
references in memory until they can be delivered to the queue?
Obviously, I could put them into a synchronized HashSet, but I'd
prefer to optimize for concurrency by minimizing locking. At the
moment, I'm using a ConcurrentHashMap, since it seems to give the best
concurrency for updates. (The usage pattern is a bit unusual, since
there are effectively no lookups. There's a put() when the reference
is created, and a remove() when it's pulled out of the reference
queue.) This is an area where I have very little experience, so I'd
welcome input from anyone who's worked with these classes.
1. Obviously, a member of RTS points to a separate statistics object
which is also pointed to by the weak reference.
The RTS object won't be collected, and so won't end up on the reference
queue, if it's held in a hashmap.