Re: destroy() method V.S. finalize() method -- JAVA400-L

OK.  It's been a L-O-N-G day.  I can't believe that I missed the HashMap
reference to the object!

Mike

----- Original Message -----
From: "Bruce Jin" <brucej@MRC-PRODUCTIVITY.COM>
To: <java400-l@midrange.com>
Sent: Thursday, November 14, 2002 6:19 PM
Subject: Re: destroy() method V.S. finalize() method


> An object gets destroyed (garbage collected) only when there is no
reference
> to it.  When one stores an object into a Map, the Map has a reference to
it.
> To destroy this object one has to remove this entry from Map in addition
to
> setting other references to null.
>
> It will be interesting to know how WeakHashMap works.
>
>
>
> Bruce
>
>
>
> ----- Original Message -----
> From: "Mike Silvers" <msilvers@HBS-INC.COM>
> To: <java400-l@midrange.com>
> Sent: Thursday, November 14, 2002 12:14 PM
> Subject: Re: destroy() method V.S. finalize() method
>
>
> >
> > I see an additional method as unnecessary overhead for the applications
> > programmer, if I can do what I am trying to do here.  I may have to
resort
> > to that method.  At first, I thought that setting the reference to null
> will
> > cause the object to be destroyed.  As I am looking into this a bit more,
I
> > am learning that simply setting an object to null will not destroy the
> > object.  There was an interesting discussion of object creation and
> > destruction in the Sun Java forums that explains allot here.
> >
> > Mike
> >
> >
> > ----- Original Message -----
> > From: "Mark Phippard" <MarkP@softlanding.com>
> > To: <java400-l@midrange.com>
> > Sent: Thursday, November 14, 2002 2:53 PM
> > Subject: Re: destroy() method V.S. finalize() method
> >
> >
> > > This is a multipart message in MIME format.
> > > --
> > > [ Picked text/plain from multipart/alternative ]
> > > What is setting the reference to null?
> > >
> > > If it is being done in code, then why not just add a method to the
> object
> > > that you call to destroy it before setting it to null?
> > >
> > > Mark
> > >
> > >
> > >
> > >
> > >
> > > "Mike Silvers" <msilvers@HBS-INC.COM>
> > > Sent by: java400-l-admin@midrange.com
> > > 11/14/2002 02:54 PM
> > > Please respond to java400-l
> > >
> > >
> > >         To:     <java400-l@midrange.com>
> > >         cc:
> > >         Subject:        Re: destroy() method V.S. finalize() method
> > >
> > >
> > > David,
> > >
> > > Here is what I am trying to accomplish:
> > >
> > > I have an object with a unique number used in the construction of the
> > > object.  I only want one instance of the particular object with that
> > > unique
> > > reference number to be in memory.  There may be multiple ob the same
> type
> > > object, but they all will have different unique numbers.
> > >
> > > What I have done is created a HashMap.  I use the unique number as the
> key
> > > (an Integer), and the object as the value.  When a new object is
> created,
> > > the reference is placed in the HashMap (a static variable for this
> class).
> > > What I need to do is when the object is destroyed (reference to null),
I
> > > need to remove the reference from the HashMap.
> > >
> > > What I have done is placed code in the finalize() method to remove the
> > > reference from the HashMap.  What I have found is that the finalize()
> > > method
> > > is not being called.
> > >
> > > I'll look into a WeakHashMap.
> > >
> > > Mike
> > >
> > > ----- Original Message -----
> > > From: "David Morris" <David.Morris@plumcreek.com>
> > > To: <java400-l@midrange.com>
> > > Sent: Thursday, November 14, 2002 2:32 PM
> > > Subject: Re: destroy() method V.S. finalize() method
> > >
> > >
> > > > Mike,
> > > >
> > > > I don't know what you are trying to accomplish and you say you
> > > > "need to remove the object from a hashmap", but an alternative may
> > > > be to use a WeakHashMap. Objects in a WeakHashMap can be
> > > > garbage collected if there is no other reference.
> > > >
> > > > David Morris
> > > >
> > > > >>> msilvers@hbs-inc.com 11/14/02 10:51AM >>>
> > > > I am creating a modification of the Singleton architecture.  I am
only
> > > > permitting one of a specific object with specific attributes.  When
I
> > > > am
> > > > performing this function, I need to remove the object reference from
a
> > > > hashmap when the object is destroyed by the user.  My question is
> > > > this....
> > > > Should I place the code for removing the object reference from the
> > > > hashmap
> > > > in the destroy() method, or the finalize() method?
> > > >
> > > > My class is going to contain a static hashmap of objects with a key
> > > > reference object.  I am concerned that either the destroy() or
> > > > finalize()
> > > > does not get called when a class is given a null reference.  I am
> > > > thinking
> > > > that one of the methods will get used for the last instance of the
> > > > class and
> > > > the other will be used for when each instance.
> > > >
> > > > any insights?
> > > >
> > > > Thanks
> > > >
> > > > Mike
> > > > _______________________________________________
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