Finalize() method for newer JVMs

Hi,
Just a quick question on finalize() if that's ok. From memory the only time the developer should have to implement this method is when you want to do something with a system resource during garbage collection.
A finalize method should never have to worry about clearing object references etc? Correct?
I am 99.9999999999% sure on this.
I am looking at some old code here which contains some objects which implement the finalise method, I am trying to figure out why they did it.
Is there any obscure case (i.e. with weak references or something) where an object may have to clear object references in finalise?
Thanks in advance.

malcolmmc wrote:
beginner2 wrote:
Hi,
Just a quick question on finalize() if that's ok. From memory the only time the developer should have to implement this method is when you want to do something with a system resource during garbage collection.
Even where you do want to do that (and it's rarely a good strategy except as some kind of backstop, since there's no guarantee you system resource related object will ever be garbage collected), I'd recommend using a PhantomReference instead. It's more controllable. You control what thread it's cleaned up on, you can pass references in a way that's dangerous in a finalize and you can discard it if (as should happen) the program explicitly closes it's connection with the resource.++agree: PhantomReference<TollBooth>

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OK, very thanks , that answer was presented on most seen place,
(not always seen).
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As far as my concept goes, the finalize() method for an object can be called only once. If it is called explicitly, the garbage collector will not call it again. But one of my programs is calling finalize() method apprantly more than once. Please see the code below.
class ObjFinalizeTest{
     public void finalize() {
          System.out.println("Class Terminated");
     static void foo() {
          ObjFinalizeTest aa = new ObjFinalizeTest();
public class Chap1 {
     static char a ;
     static int b ;
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ObjFinalizeTest@923e30
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Finalize is just like any other method, it's nothing special, same with main. What you are doing is explicitly calling it and then the JVM is calling it as well. I think the docs only state that the JVM will only call the method once, you however can call it as many times as you like.

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import java.io.*;
import com.db.ui.*;
import java.util.*;
* @author DBriscoe
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Every time a User object is created, a static counter variable is incremented and then when an object is destroyed it appends the current value of that static member to the Tomcat log file (via System.out.println being executed on server side).
Below is the log file from an example run in my webapp.
Dustin
User Queue Empty, Adding User: com.db.multi.User@1a5af9f
User Dustin destroyed. 0
User Dustin destroyed. 0
User Dustin destroyed. 0
User Dustin destroyed. 0
User Dustin destroyed. 0
USER QUEUE: false
INSIDE METHOD: false
AFTER METHOD: false
User Dustin destroyed. 1
User Dustin destroyed. 1
User Dustin destroyed. 1
User Dustin destroyed. 1
USER QUEUE: false
INSIDE METHOD: false
AFTER METHOD: false
User Dustin destroyed. 2
User Dustin destroyed. 2
User Dustin destroyed. 2
User Dustin destroyed. 2
User Dustin destroyed. 2
User Dustin destroyed. 2
User Dustin destroyed. 2
User Dustin destroyed. 2
USER QUEUE: false
INSIDE METHOD: false
AFTER METHOD: false
User Dustin destroyed. 3
User Dustin destroyed. 3
User Dustin destroyed. 3
User Dustin destroyed. 3
User Dustin destroyed. 3
User Dustin destroyed. 3
User Dustin destroyed. 3
User Dustin destroyed. 3
User Dustin destroyed. 3
USER QUEUE: false
INSIDE METHOD: false
AFTER METHOD: false
User Dustin destroyed. 4
User Dustin destroyed. 4
User Dustin destroyed. 4
User Dustin destroyed. 4
User Dustin destroyed. 4
User Dustin destroyed. 4
User Dustin destroyed. 4
User Dustin destroyed. 4
User Dustin destroyed. 4
USER QUEUE: false
INSIDE METHOD: false
AFTER METHOD: false
User Dustin destroyed. 5
User Dustin destroyed. 5
User Dustin destroyed. 5
User Dustin destroyed. 5
User Dustin destroyed. 5
User Dustin destroyed. 5
User Dustin destroyed. 5
User Dustin destroyed. 5
User Dustin destroyed. 5
USER QUEUE: false
INSIDE METHOD: false
AFTER METHOD: false
User Dustin destroyed. 6
User Dustin destroyed. 6
User Dustin destroyed. 6
User Dustin destroyed. 6
User Dustin destroyed. 6
User Dustin destroyed. 6
User Dustin destroyed. 6
User Dustin destroyed. 6
User Dustin destroyed. 6
User Dustin destroyed. 6
Joe
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INSIDE METHOD: false
AFTER METHOD: false
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User Already Placed: Dustin with Joe
User Dustin destroyed. 7
User Dustin destroyed. 7
User Dustin destroyed. 7
User Dustin destroyed. 7
User Dustin destroyed. 7
User Dustin destroyed. 7
User Dustin destroyed. 7
User Dustin destroyed. 7
User Dustin destroyed. 7
User Dustin destroyed. 7
INSIDE METHOD: false
INSIDE METHOD: false
USER QUEUE: true
INSIDE METHOD: false
INSIDE METHOD: false
User Dustin destroyed. 9
User Joe destroyed. 9
User Dustin destroyed. 9
User Dustin destroyed. 9
User Dustin destroyed. 9
User Dustin destroyed. 9
INSIDE METHOD: true
INSIDE METHOD: false
USER QUEUE: true
INSIDE METHOD: false
INSIDE METHOD: false
INSIDE METHOD: true
INSIDE METHOD: false
USER QUEUE: true
INSIDE METHOD: false
INSIDE METHOD: false
It really does seem to me like finalize is being called multiple times for the same object.
That number should incremement for every instantiated User, and finalize can only be called once for each User object.
I thought this was impossible?
Any help is appreciated!

Thanks...
I am already thinking of ideas to limit the number of threads.
Unfortunately there are two threads of execution in the servlet handler, one handles requests and the other parses the collection of User objects to check for out of date timestamps, and then eliminates them if they are out of date.
The collection parsing thread is currently a javax.swing.Timer thread (Bad design I know...) so I believe that I can routinely check for timestamps in another way and fix that problem.
Just found out too that Tomcat was throwing me a ConcurrentModificationException as well, which may help explain the slew of mysterious behavior from my servlet!
The Timer thread has to go. I got to think of a better way to routinely weed out User objects from the collection.
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Hi
I need some help in overwriting the finalize() method.
I have a program, but at certain points, i would like to "kill" a particular object.
I figured that the only way to do that is to make that object's class override the finalize method, and call it when i need to kill the object.
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To, as you put it, kill an object, just null it. This
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Finalize() method for newer JVMs

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