There is an alternative in the current structure: Give each
VeryComplexObject a resource recovery queue, and a resource recovery
thread dedicated to removing items from the queue and executing them.
The finalizer would construct and queue up a resource recovery request,
but not try to do any recovery itself.

However, this would make VeryComplexObject even more complex, which does
not seem like a good idea. I think some refactoring with the aim of
making this easier would be a better plan.

Patricia

First of all, everything robert said is perfectly valid.

Now, calling runFinalization() does nothing more than hint the JVM to put
more effort into calling the finalize() method of objects pending removal
(in other words, objects that the GC will clean up at some point in the
future). Basically, unless you have a really good reason (and i cant really
think of one), dont touch that method.

Secondly, it's a bad idea to do anything in any finalize() method that can
potentially block. For example, instead of removing something from your
complex object in the finalize() method you could start a seperate thread
that does the removing instead (obviously you must not pass a reference to
the object being finalised to that thread or you'd be ressurecting your
simple object).

Finally, counting on finalizers to do anything but clean up native resources
or implement some sort of object reuse scheme is probably bad design, so i
strongly suggest you reconsider your options and look for a more clean
approach. Perhaps if you give some additional info i can suggest
alternatives. Good luck.

- Remon van Vliet

I don't think it's contrived at all, but very typical.

Instead of "complex object", "simple object", think server and client.

In the case where serveral client objects are consuming resources on the
server object, and you want to dismiss the server object, while at the
same time not hanging the clients -- but notifying them that "hey, the
server just went away, so when you need to close, just go ahead".

This would suggest to me just such an arrangement, where a closing /Very
ComplexObject/ needs to notify all "SimpleObjects" that consume it, that
it is going away.

Alternatively, in the finally() clause where you would try and "remove
some data" there would be another try/catch, that would catch an
exception if VeryComplexObject no longer exists, and then continue on to
finalize SimpleObject.

I don't think it's contrived at all, but very typical.

Instead of "complex object", "simple object", think server and client.

In the case where serveral client objects are consuming resources on the
server object, and you want to dismiss the server object, while at the
same time not hanging the clients -- but notifying them that "hey, the
server just went away, so when you need to close, just go ahead".

This would suggest to me just such an arrangement, where a closing /Very
ComplexObject/ needs to notify all "SimpleObjects" that consume it, that
it is going away.

Alternatively, in the finally() clause where you would try and "remove
some data" there would be another try/catch, that would catch an
exception if VeryComplexObject no longer exists, and then continue on to
finalize SimpleObject.

Robert Klemme a écrit :

i need to. I'm using MappedByteBuffer, which don't have an unmap method,
and which are limited (in number * size). So i need them to be freed
before being able to allocate new ones. The code looks like this:

while (!success && tries < maxTries) {
  try {
    MappedByteBuffer buffer = fc.map(...);
    success = true;
  } catch (IOException ex) {
    boolean noMoreMem = ex.getMessage().equals("Cannot allocate memory");

    if (noMoreMem) {
      System.gc();
      System.runFinalization();

      tries++;
    } else {
      throw ex;
    }
  }
}

if (tries >= maxTries) {
  // fatal error
}

i can't distribute information

the "delaying cleanup" idea is pretty good. I think i will use the
"resource recovery queue" of Patricia.

Remon:

starting another thread might be the solution. The thread will wait
without problem the lock release.

I didn't choose the design of the the app, i'm an employee. Sorry but i
can't rewrite everything from scratch. I have to use it like this.

Thx to you all for your apreciated help.