Re: Data structure to keep things in memory

From:
"Mike Schilling" <mscottschilling@hotmail.com>
Newsgroups:
comp.lang.java.programmer
Date:
Mon, 29 Nov 2010 08:20:13 -0800
Message-ID:
<id0js3$s6j$1@news.eternal-september.org>
"Steven Simpson" <ss@domain.invalid> wrote in message
news:liacs7-472.ln1@news.simpsonst.f2s.com...

On 28/11/10 20:43, Mike Schilling wrote:

"Steven Simpson" <ss@domain.invalid> wrote in message
news:5kpas7-paa.ln1@news.simpsonst.f2s.com...

Maybe you can get away with a ConcurrentMap<Key, RTSUser>, if you want
to avoid synchronization:


ConcurrentMap is what I'm using. The consensus seems to be that it's
the best choice.


I understand your OP better now. Basically, it seems you already had
the structures we were talking about:

1. Obviously, a member of RTS points to a separate statistics object
which is also pointed to by the weak reference.


Your RTS is the RTSHandle. Your 'separate statistics object' is RTSImpl.

So you need a container of RTSUsers. That was served by the
Map<Reference<RTSHandle>, RTSImpl> in ClassCastException's original
suggestion, and a Collection<RTSUser> will suffice here.


Your weak reference is my RTSUser. You're using a ConcurrentMap (of
<Reference<RTS>, Boolean>, I presume) as a kind of set, which
corresponds to the Collection<RTSUser> above, used to hang on to
references.

Actually, you must have extended WeakReference in order to point it
(strongly) at the separate statistics object...?


Yes.

Or you're already using a ConcurrentMap<Reference<RTS>,
SeparateStatisticsObject> as CCE
suggested.

(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.)


To make it a little less unusual, can you afford to use
Collections.newSetFromMap here, since you're only using normal puts and
removes?


That was introduced in 1.6, and I need it to compile with 1.5

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