Re: System.gc()

Eric Sosman <esosman@ieee-dot-org.invalid>
Wed, 26 Aug 2009 10:17:37 -0400
Lew wrote:

Eric Sosman wrote:

Lew wrote:

Ross wrote:

Looking through everything written, and thinking, I added a static int
to some of my classes. Then, I incremented that value in constructors,
and decremented in finalize().

So your application is single-threaded, then.

    No. (Hint: Does finalize() run on the same thread that
runs the constructors?)

Then one wonders how he avoided synchronization issues on the static
instance counter.

     Just a suspicion: He may not have realized he *has*
synchronization issues. (He's not the first to overlook
such a possibility. I deal regularly with a third-party
application that keeps track of the number of user sessions
that are active, and sometimes when they all log off it
happily reports -1 sessions ... Can't you just *smell* an
unsynchronized counter that lost an up-tick?)

     Easiest solution is probably to change the counter from
a plain `int' to an AtomicInteger. Note that `volatile' is
*not* a solution; increment or decrement needs both a read
and a write, and `volatile' will not glue the two operations
together inseparably.

Eric Sosman

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