Problem about finalize() method
when will the finalize() execute?At the time the associated object is no longer available or at the time the next garbage collection happen ?
When problem with jdbc,I must use connection in the object.And I want to release the connection at the moment the object disposed(no longer available).Can finalize method do this,if can not ,Any other method?
finalize() is called when the garbage collector is collecting the object. see http://java.sun.com/docs/books/jls/second_edition/html/execution.doc.html#44748
Similar Messages
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About calling method with arguments
Hi,
I have a problem about calling method using reflection. my method is like follows:
public myMethod(Integer var1, MyObject mobj) {
I've tried to call the method using the following code,
Class[] parameterTypes = new Class[] {Integer.class, MyObject.class};
Object[] arguments = new Object[] {new Integer(2), mobj};
Method met=cl.getMethod("myMethod", parameterTypes);
But the in the last line NoSuchMethodException is thrown.
How can I send the reference of MyObject to myMethod()?
Thanx
ronyShould work ok:
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
public class Test {
static class MyObject {}
public static void main(String[] args) throws Exception {
Class c = Test.class;
Class[] parameterTypes = new Class[] {Integer.class, MyObject.class};
try {
Object[] arguments = new Object[] {new Integer(2), new MyObject()};
Method met = c.getMethod("myMethod", parameterTypes);
met.invoke(new Test(), arguments);
} catch (NoSuchMethodException e) {
System.out.println(e);
} catch (IllegalAccessException e) {
System.out.println(e);
} catch (InvocationTargetException e) {
System.out.println(e);
public void myMethod(Integer var1, MyObject mobj) {
System.out.println("myMethod");
} -
What happens when an exception occurs at finalize method ?
What happens when an exception occurs at the time of cleaning objects in finalize methods?
Will program crashes?1.) Why don't you try it? You can simply throw your own exception.
2.) For this kind of questions the JVM specification is a good resource, for your concrete problem the chapter about finalization might be interested (look for the sentence starting with "If an uncaught exception ..."). -
A question about a method with generic bounded type parameter
Hello everybody,
Sorry, if I ask a question which seems basic, but
I'm new to generic types. My problem is about a method
with a bounded type parameter. Consider the following
situation:
abstract class A{ }
class B extends A{ }
abstract class C
public abstract <T extends A> T someMethod();
public class Test extends C
public <T extends A> T someMethod()
return new B();
}What I want to do inside the method someMethod in the class Test, is to
return an instance of the class B.
Normally, I'm supposed to be able to do that, because an instance of
B is also an instance of A (because B extends A).
However I cannot compile this program, and here is the error message:
Test.java:16: incompatible types
found : B
required: T
return new B();
^
1 errorany idea?
many thanks,Hello again,
First of all, thank you very much for all the answers. After I posted the comment, I worked on the program
and I understood that in fact, as spoon_ says the only returned value can be null.
I'm agree that I asked you a very strange (and a bit stupid) question. Actually, during recent months,
I have been working with cryptography API Core in Java. I understood that there are classes and
interfaces for defining keys and key factories specification, such as KeySpec (interface) and
KeyFactorySpi (abstract class). I wanted to have some experience with these classes in order to
understand them better. So I created a class implementing the interface KeySpec, following by a
corresponding Key subclass (with some XOR algorithm that I defined myself) and everything was
compiled (JDK 1.6) and worked perfectly. Except that, when I wanted to implement a factory spi
for my classes, I saw for the first time this strange method header:
protected abstract <T extends KeySpec> T engineGetKeySpec
(Key key, Class<T> keySpec) throws InvalidKeySpecExceptionThat's why yesterday, I gave you a similar example with the classes A, B, ...
in order to not to open a complicated security discussion but just to explain the ambiguous
part for me, that is, the use of T generic parameter.
The abstract class KeyFactorySpi was defined by Sun Microsystem, in order to give to security
providers, the possibility to implement cryptography services and algorithms according to a given
RFC (or whatever technical document). The methods in this class are invoked inside the
KeyFactory class (If you have installed the JDK sources provided by Sun, You can
verify this, by looking the source code of the KeyFactory class.) So here the T parameter is a
key specification, that is, a class that implements the interface KeySpec and this class is often
defined by the provider and not Sun.
stefan.schulz wrote:
>
If you define the method to return some bound T that extends A, you cannot
return a B, because T would be declared externally at invocation time.
The definition of T as is does not make sense at all.>
He is absolutely right about that, but the problem is, as I said, here we are
talking about the implementation and not the invocation. The implementation is done
by the provider whereas the invocation is done by Sun in the class KeyFactory.
So there are completely separated.
Therefore I wonder, how a provider can finally impelment this method??
Besides, dannyyates wrote
>
Find whoever wrote the signature and shoot them. Then rewrite their code.
Actually, before you shoot them, ask them what they were trying to achieve that
is different from my first suggestion!
>
As I said, I didn't choose this method header and I'm completely agree
with your suggestion, the following method header will do the job very well
protected abstract KeySpec engineGetKeySpec (Key key, KeySpec key_spec)
throws InvalidKeySpecException and personally I don't see any interest in using a generic bounded parameter T
in this method header definition.
Once agin, thanks a lot for the answers. -
An old and difficult problem about "UnsatisfiedLinkError"
Hi dear all,
I have been struck with the problem about "UnsatisfiedLinkError". I have a c++ class HelloWorld with a method hello(), and I want to call it from within a java class. In fact, I have succeeded in calling it on the windows platform. But when I transfer it to linux, the error "UnsatisfiedLinkError" comes out. I have tried to take the measures as Forum has suggested, but it failed.
The source code is very simple to demonstrate JNI.
"HelloWorld.h"
#ifndef INCLUDEDHELLOWORLD_H
#define INCLUDEDHELLOWORLD_H
class HelloWorld
public:
void hello();
#endif
"HelloWorld.cpp"
#include <iostream>
#include "HelloWorld.h"
using namespace std;
void HelloWorld::hello()
cout << "Hello, World!" << endl;
"JHelloWorld.java"
public class JHelloWorld
public native void hello();
static
System.loadLibrary("hellolib");
public static void main(String[] argv)
JHelloWorld hw = new JHelloWorld();
hw.hello();
"JHelloWorld.cpp"
#include <iostream>
#include <jni.h>
#include "HelloWorld.h"
#include "JHelloWorld.h"
JNIEXPORT void JNICALL Java_JHelloWorld_hello (JNIEnv * env, jobject obj)
HelloWorld hw;
hw.hello();
All the files are in the same directory and all the processes are under the dirctory:
1. javac JHelloWorld.java
2. javah -classpath . JHelloWorld
3. g++ -c -I/usr/java/jdk1.3/include -I/usr/java/jdk1.3/include/linux JHelloWorld.cpp HelloWorld.cpp
4. ld -shared -o hellolib.so *.o
5. java -cp . -Djava.library.path=. JHelloWorld
Exception in thread "main" java.lang.UnsatisfiedLinkError: no hellolib in java.library.path
at java.lang.ClassLoader.loadLibrary(ClassLoader.java:1349)
at java.lang.Runtime.loadLibrary0(Runtime.java:749)
at java.lang.System.loadLibrary(System.java:820)
at JHelloWorld.<clinit>(JHelloWorld.java:7)
Tried another measure:
i) export LD_LIBRARY_PATH=.:$LD_LIBRARY_PATH
ii)java -cp . JHelloWorld
The same error came out as above.
I really don't know what is wrong with it.
Would you like to help me as soon as possible?
Thanks.
Regards,
JohnsonHi Fabio,
Thanks a lot for your help.
It is very kind of you.
Regards,
Johnson -
Finalize() method being called multiple times for same object?
I got a dilly of a pickle here.
Looks like according to the Tomcat output log file that the finalize method of class User is being called MANY more times than is being constructed.
Here is the User class:
package com.db.multi;
import java.io.*;
import com.db.ui.*;
import java.util.*;
* @author DBriscoe
public class User implements Serializable {
private String userName = null;
private int score = 0;
private SocketImage img = null;
private boolean gflag = false;
private Calendar timeStamp = Calendar.getInstance();
private static int counter = 0;
/** Creates a new instance of User */
public User() { counter++;
public User(String userName) {
this.userName = userName;
counter++;
public void setGflag(boolean gflag) {
this.gflag = gflag;
public boolean getGflag() {
return gflag;
public void setScore(int score) {
this.score = score;
public int getScore() {
return score;
public void setUserName(String userName) {
this.userName = userName;
public String getUserName() {
return userName;
public void setImage(SocketImage img) {
this.img = img;
public SocketImage getImage() {
return img;
public void setTimeStamp(Calendar c) {
this.timeStamp = c;
public Calendar getTimeStamp() {
return this.timeStamp;
public boolean equals(Object obj) {
try {
if (obj instanceof User) {
User comp = (User)obj;
return comp.getUserName().equals(userName);
} else {
return false;
} catch (NullPointerException npe) {
return false;
public void finalize() {
if (userName != null && !userName.startsWith("OUTOFDATE"))
System.out.println("User " + userName + " destroyed. " + counter);
}As you can see...
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
USER QUEUE: false
INSIDE METHOD: false
AFTER METHOD: false
User Dustin pulled from Queue, Game created: Joe
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.
Or perhaps, maybe I can attempt to make it thread safe???
Eg. make my User collection volatile?
Any opinions on the best approach are well appreciated. -
A problem about calling Labview vi in VB
Hi all:
I meeting a problem about data transfer and parallel operation between VB and Labview.
Actually, I want develop a VB program, in which, the Labview VI can be called and corresponding parameters can be transferred to Labview. and then, I also can operate my system by VB program at same time. something like parallel operation (VB and Labview program).
But the question is :
1. If I use "Call" method of ActiveX in VB, and the LabVIEW subvi is not stopped (for example, a loop structure), I can not do parallel operation on VB program. The error message is "other application is busy" which is attached below. The sample codes is also attached.
2. I tried to use other methods like "OpenFrontPanel" and "Run", but I am not sure how to transfer the parameter??
3. Then I tried to use "SetControlValue" to set the parameters, but there is a error " := expected", which is very strange, because the statement I wrote is followed with the help documents [ eg: VI.SetControlValue ("string", value)], why it is still need a "=" ??
Does anybody know something about it? Thanks a lot
Message Edited by hanwei on 11-07-2008 03:18 PM
Attachments:
vb_labview_error_message_1.JPG 14 KB
VB_to_LV.zip 10 KBI sure hope OP has solved it by now.
/Y
LabVIEW 8.2 - 2014
"Only dead fish swim downstream" - "My life for Kudos!" - "Dumb people repeat old mistakes - smart ones create new ones."
G# - Free award winning reference based OOP for LV -
Help needed in overriding the finalize() method!
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.
Once that is done, i would call the garbage collector gc() to hopefully dispose of it.
Please assist me?
Thanks
RegardsTo, as you put it, kill an object, just null it. This
will be an indication for the garbage collector to
collect the object. In the finalizer, you marely null
all fields in the class. Like this:
public class DummyClass
String string = "This is a string";
Object object = new Boolean(true);
public void finalize() throws Throwable
super.finalize();
string = null;
object = null;
public static void main(String[] args)
//Create a new object, i.e allocate an
te an instance.
DummyClass cls = new DummyClass();
//Null the reference
cls = null;
This is a pointless exercise. If an object is being finalized, then all the references it contains are about to cease being relevant anyway, so there's no purpose to be served in setting them to null.
All that clearing a reference to an object does is to clear the reference. Whether the object is subsequently finalized depends on whether the object has become unreachable.
Directly calling finalize is permitted, but doesn't usually serve any purpose. In particular, it does not cause the object to be released. Further, calling the finalize method does not consitute finalization of the object. Finalization occurs when the method is called as a consequence of a garbage collector action.
If a variable contains a reference to an object (say a table), and you want a new table instead, then create a new table object, and assign its reference to the variable. Assuming that the variable was the only place that the old table's reference was stored, the old table will, sooner or later, get finalized and collected.
Sylvia. -
Problems with secondary methods in workflow
Hi experts.
I am starting my WF through the SAP_WAPI_START_WORKFLOW in SE37.
My WF consistst of a decision step with a secondary method, amodal method, which calls a custom method (call_url).
The method call_url has been tested in SE80 and in WF with synchronous dialog chain(BMWP) where it works fine.
Since UWL doesn`t support Synchronous dialog chain, I need to make a workaround.
Problem:
When I start the WF and enter MSS to open the workitem, I can see the attachment (call_url method). However, when I try to click on the link for the attachment (which is going to execute my custom method) I only get an errormessage.
The errormessage says:
"An error has occured during calling attachment. Try again and inform the system administrator about this problem".
I have been checkin SU53, it is not an authorization issue.
I have been reading Gatlings blog about secondary methods and searching the web about the issue with no luck.
Any ideas how to solve it?
<<text removed>>
Thanks in advance.
Best regards,
Tor
Edited by: Matt on Feb 10, 2009 5:06 PM - please do not offer rewards. Please do read the Terms of Engagement of these forumsOk, now i'm a little bit closer to the solution.
I've run thru the programm in debugging mode...
the reason is: function module SWO_INVOKE give me the return message OL850: You do not have authorization to execute method EDIT
But when the user calls the transaction ME52n everything is ok.
So what is the missing authorization object?
Thank you very much in advance
Andrey -
Problem about get the workflow context
There are 2 servers.
One is Weblogic server (server1), deployed a fusion web project on it.
Another is BPM server (server2), deployed the bpm process on it.
On the fusion web project, we use API to get the tasks. But we encountered a problem about get the workflow context.
There are 2 method to get the workflow context.
1. getTaskQueryService().authenticate(userId, password, null, null), this method need to pass in useId and password, we can get the user form request but can't get
password.
2. getTaskQueryService().createContext(request), we pass the request on server1, but can't get the context on server2, exception thrown.
Appreciate if you can give some help.javax.el.ELException: java.lang.SecurityException: [Security:090398]Invalid Subject: principals=[jcooper, ERole]
at javax.el.BeanELResolver.getValue(BeanELResolver.java:266)
at com.sun.faces.el.DemuxCompositeELResolver._getValue(DemuxCompositeELResolver.java:173)
at com.sun.faces.el.DemuxCompositeELResolver.getValue(DemuxCompositeELResolver.java:200)
at com.sun.el.parser.AstValue.getValue(Unknown Source)
at com.sun.el.ValueExpressionImpl.getValue(Unknown Source)
Truncated. see log file for complete stacktrace
Exception thrown when createContext() -
Java API - finalize method for XmlResults
Hello!
I'm wondering why in DB XML Java code we have a finalize() method which invokes delete() method whereas we are supposed to invoke delete() method manually (according to the documentation). Is it ok if delete() method is invoked twice (it happens in case GC cleans up the XmlResults object) ? Can't we get some problems because of that?
Thanks,
VyacheslavAlso you should note that Java actually makes no guarantees that the finalize() method is called, and it can frequently happen in practice that this is the case. For instance, the JVM usually doesn't bother calling finalize() on objects if it is shutting down, which can be disastrous for DB XML objects like Environment, XmlManager and XmlContainer, which need to clean up and write data to disk when they are closed. Read the [FAQ | http://www.oracle.com/technology/products/berkeley-db/faq/xml_faq.html#16] for more details.
John -
Problem about selecting waveform in waveform graph
Hi all:
I am developing a project by Labview. Now I meet a problem about selecting the waveform in the waveform graph.
I am not sure whether it is possible about my idea.
for example:
In the waveform graph, the different waveforms from a couple of channels are displayed. and then I want to select one waveform of them, and corresponding data about this waveform are shown.
Thanks so lot
regardshanwei wrote:
1. can I zoom in and out in that "waveform graph"??
You can do this using the graph palette. Just make it visible. The middle control allows you to zoom.
2. can I display the plot array or plot index that I select in the waveform graph?
You can connect the same wire that goes to the ActivePlot property node to an indicator.
3. I build a sample codes for my project, in which , I used a random number generater to simulate a DAQmx data collection, and generate a overlapping waveform in the waveform graph.
but it seems the program is not stable, when i first run the codes, it is ok, and I can select the plot what I want. but after I stop and restart the program, there is error message about "Property Node".
it seems something wrong about the "waveform graph properties"
I attached my codes here, anybody know what wrong about it?
For some strange reason the property node is "messed up". I've seen this happen sometimes with graphs. I don't know what causes it, and the only way I've found to fix the problem is to delete the graph, put a new one on the front panel, and recreate the property nodes. I've typically seen this happen when copying code from another VI that has a graph with property nodes, as I suspect you did. If you delete the graph, put a new one on there, and recreate the property node you should be OK.
That said, a few comments regarding the code:
The architecture seems to be a mish-mash of operations, and I'm thinking that you probably want to look at using a producer-consumer architecture. Your producer loop responds to events, and the consumer loop does your DAQ collection.
You have a race condition with your use of the "size(s) 2" local variable.
Avoid right-to-left wires.
The method of creating your arrays seems convoluted. However, since you said you will actually be getting the data from a DAQ system, the actual project code will likely be considerably different. -
Can anybody post me simple programme of finalize() method ?
i have read as theoretically what is garbage collection and using finalize() method one can achieve but as a student i want to know simple program like we had destructor in c++
thank youThe finalize() method is described in the Object's API documentation.
http://java.sun.com/javase/6/docs/api/java/lang/Object.html
What is noticable from that description is how few guarantees the method makes. My advice would be don't use it.
In particular if you try and use finalize() to clean up resources you will face a couple of problems:
(1) Garbage collection might not ever run.
(2) Across multiple objects, finalize order is not predictable.
A better technique for dealing with the "resources" problem - using the finally keyword and an explicit close() method is described here:
http://java.sun.com/developer/TechTips/2000/tt0124.html -
The Problem about Monitoring Motion using PCI-7358 on LabVIEW Real Time Module
Hello everyone,
I have a problem about monitoring the position of an axis. First let me give some details about the motion controller system I’m using.
I’m using PCI-7358 as controller and MID-7654 as servo driver, and I’m controlling a Maxon DC Brushed motor. I want to check the dynamic performance of the actuator system in a real time environment so I created a LabVIEW function and implemented it on LabVIEW Real Time module.
My function loads a target position (Load Target Position.vi) and starts the motion. (Start.vi) then in a timed loop I read the instantaneous position using Read Position.vi. When I graphed the data taken from the Read Position.vi, I saw that same values are taken for 5 sequential loops. I checked the total time required by Read Position.vi to complete its task and it’s 0.1ms. I arranged the loop that acquires the data as to complete its one run in 1ms. But the data shows that 5 sequential loops read the same data?Read Position.flx can execute much faster than 5 ms but as it reads a register that is updated every 5 ms on the board, it reads the same value multiple times.
To get around this problem there are two methods:
Buffered High-Speed-Capturing (HSC)
With buffered HSC the board stores a position value in it's onboard buffer each time a trigger occurrs on the axis' trigger input. HSC allows a trigger rate of about 2 kHz. That means, you can store a position value every 500 µs. Please refer to the HSC examples. You may have to look into the buffered breakpoint examples to learn how to use a buffer, as there doesn't seem to be a buffered HSC example available. Please note that you need an external trigger-signal (e. g. from a counter of a DAQ board). Please note that the amount of position data that you can acquire in a single shot is limited to about 16.000 values.
Buffered position measurement with additional plugin-board
If you don't have a device that allows you to generate a repetitive trigger signal as required in method 1.), you will have to use an additional board, e. g. a PCI-6601. This board provides four counter/timers. You could either use this board to generate the trigger signal or you could use it to do the position capturing itself. A PCI-6601 (or an M-Series board) provides can run a buffered position acquisition with a rate of several hundred kHz and with virtually no limitation to the amount of data to be stored. You could even route the encoder signals from your 7350 to the PCI-6601 by using an internal RTSI cable (no external wiring required).
I hope this helps,
Jochen Klier
National Instruments -
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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