DGCserver problem.......

I am using the RDBMSRealm security provided in the
examples for my custom security in my application.It works fine for
sometime and once i encounter the following lines in the weblogic.log
file, it gives me SecurityException there after....
And if i restart the Sever it works fine for sometime and again when
the above line appear it again gives the exception.What is this
"DGCserver".I couldn't find anything about it in the
documentation.Please give me a workaround ASAP.
I am using
JDK : JDK1.2.2
Server : WebLogicServer5.1
Database : OracleServer 8.1.6
JDBC Driver: Oracle thin Driver
WebServer : Apache 8.3.12
ServletEngine : ServletExec3.0.
The error I get get in the WebLogic.log file:
Thu Nov 02 13:56:33 GMT+05:30 2000: <DGCserver> tried to renew
lease for 1 lost reference(s).
Thu Nov 02 13:56:33 GMT+05:30 2000: <DGCserver> tried to renew
lease for 1 lost reference(s).
Thu Nov 02 13:56:33 GMT+05:30 2000: <DGCserver> tried to renew
lease for 1 lost reference(s).
Thu Nov 02 13:56:33 GMT+05:30 2000: <DGCserver> tried to renew
lease for 1 lost reference(s).
Thu Nov 02 13:56:33 GMT+05:30 2000: <DGCserver> tried to renew
lease for 1 lost reference(s).
Thu Nov 02 13:56:33 GMT+05:30 2000: <DGCserver> tried to renew
lease for 1 lost reference(s).
Thu Nov 02 13:57:34 GMT+05:30 2000: <DGCserver> tried to renew
lease for 1 lost reference(s).
Thu Nov 02 13:57:34 GMT+05:30 2000: <DGCserver> tried to renew
lease for 1 lost reference(s).
Thu Nov 02 13:57:34 GMT+05:30 2000: <DGCserver> tried to renew
lease for 1 ! lost reference(s).
Thu Nov 02 13:57:34 GMT+05:30 2000: <DGCserver> tried to renew
lease for 1 lost reference(s).
Thu Nov 02 13:57:34 GMT+05:30 2000: <DGCserver> tried to renew
lease for 1 lost reference(s).
Thu Nov 02 13:57:34 GMT+05:30 2000: <DGCserver> tried to renew
lease for 1 lost reference(s).
Thu Nov 02 13:58:32 GMT+05:30 2000: <DGCserver> tried to renew
lease for 1 lost reference(s).
Thu Nov 02 13:58:32 GMT+05:30 2000: <DGCserver> tried to renew
lease for 1 lost reference(s).
Thu Nov 02 13:58:32 GMT+05:30 2000: <DGCserver> tried to renew
lease for 1 lost reference(s).
Thu Nov 02 13:58:32 GMT+05:30 2000: <DGCserver> tried to renew
lease for 1 lost reference(s).
Thu Nov 02 13:58:32 GMT+05:30 2000: <DGCserver> tried to renew
lease for 1 lost reference(s).

Hi, Beverley.
Thank you for visiting Apple Support Communities.
I understand that you are unable to trim clips using iMovie. I would need a little more information on how you were attempting to trim a clip to provide a better answer. However, make sure you have the movie project open and are selecting the clip that you wish to trim as this will activate the clip trimmer.
Trim clips
-Jason H.

Similar Messages

DGCserver messages in log... "Tried to renew lease on lost reference"

Hi,
 I am running weblogic server 6.1 and get the following messages
 ####<Jan 30, 2002 2:36:55 PM CST> <Info> <DGCserver> <MBarton> <myserver> <ExecuteThread: '12' for queue: 'default'> <> <> <000000> <Tried to renew lease on lost reference: '706'>
 I have seen in the newsgroup that this was a problem previously in version 4.5.1
 any help would be appreciated.
 best regards,
 Mickey


 This shouldn't cause any problems. Does it? We will turn off these info messages.
 Cheers,
 -- Prasad
 Mickey Barton <[email protected]> wrote:
 >Hi,
 >I am running weblogic server 6.1 and get the following messages
 >
 >####<Jan 30, 2002 2:36:55 PM CST> <Info> <DGCserver> <MBarton> <myserver>
 ><ExecuteThread: '12' for queue: 'default'> <> <> <000000> <Tried to
 >renew lease on lost reference: '706'>
 >
 >I have seen in the newsgroup that this was a problem previously in version
 >4.5.1
 >
 >any help would be appreciated.
 >
 >best regards,
 >Mickey

DGCServer messages in log... "tried to renew lease"

Hi,
 I'm running three WL 4.5.2 servers clustered, JDK1.1.7b on Solaris 2.6.
 Normally the cluster runs just fine, but now I'm beginning to see the
 following message in all three servers:
 <DGCserver> tried to renew lease for lost ref: nnn
 Usually they come in small bursts of about 5 or 10 messages that are the
 same, except the "ref"s keep increasing. I'm guessing it has to do something
 with the in-memory replication of sessions (which I'm using).
 Any ideas? I tried restarting the servers but after a little while the
 messages started again.
 Thanks,
 Matias


One common symptom for this (Bad Status Exception) has been long gc. If gc
 takes more 30 seconds then you will start seeing these errors. To assertain
 this, you could turn on weblogic.debug.cluster=1 and if you see a message "Timed
 out server" in the log then you should tune your server.
 Please use latest service packs.
 thanks
 - Prasad
 Matias Pelenur wrote:
 > Well, after a few restarts the DGC messages aren't appearing anymore... But
 > something different is happening now which seems to be worse... And it's
 > affecting performance too. For some pages, one of the servers will throw a
 > bunch of exceptions (see below), and it seems it's cutting off the output so
 > pages get only half-created. Any ideas? I don't think I changed any settings
 > or anything like that.
 >
 > Thanks,
 > Matias
 >
 > Fri Sep 15 11:19:15 EDT 2000:<E> <HTTP> Servlet request terminiated with
 > Error:
 > Fri Sep 15 11:19:15 EDT 2000:<E> <HTTP>
 > weblogic.cluster.replication.BadStatusException: update found
 > 1802540915606489052 but it is not the secondary
 > at weblogic.rmi.extensions.BasicRequest.sendReceive(Compiled Code)
 > at
 > weblogic.cluster.replication.ReplicationManager_WLStub.update(Compiled Code)
 > at
 > weblogic.cluster.replication.ReplicationManager.updateSecondary(Compiled
 > Code)
 > at weblogic.servlet.internal.session.ReplicatedSession.sync(Compiled
 > Code)
 > at
 > weblogic.servlet.internal.session.ReplicatedSessionContext.sync(Compiled
 > Code)
 > at weblogic.servlet.internal.ServletRequestImpl.syncSession(Compiled
 > Code)
 > at
 > weblogic.servlet.internal.ServletContextImpl.invokeServlet(Compiled Code)
 > at
 > weblogic.servlet.internal.ServletContextImpl.invokeServlet(Compiled Code)
 > at weblogic.socket.MuxableSocketHTTP.invokeServlet(Compiled Code)
 > at weblogic.socket.MuxableSocketHTTP.execute(Compiled Code)
 > at weblogic.t3.srvr.ExecuteThread.run(Compiled Code)
 > --------------- nested within: ------------------
 > weblogic.utils.NestedError: Tried to update secondary, but it thought it was
 > the primary
 > - with nested exception:
 > [weblogic.cluster.replication.BadStatusException: update found
 > 18025409156064890
 > 52 but it is not the secondary]
 > at java.lang.Throwable.<init>(Compiled Code)
 > at java.lang.Error.<init>(Compiled Code)
 > at weblogic.utils.NestedError.<init>(Compiled Code)
 > at weblogic.servlet.internal.session.ReplicatedSession.sync(Compiled
 > Code)
 > at
 > weblogic.servlet.internal.session.ReplicatedSessionContext.sync(Compiled
 > Code)
 > at weblogic.servlet.internal.ServletRequestImpl.syncSession(Compiled
 > Code)
 > at
 > weblogic.servlet.internal.ServletContextImpl.invokeServlet(Compiled Code)
 > at
 > weblogic.servlet.internal.ServletContextImpl.invokeServlet(Compiled Code)
 > at weblogic.socket.MuxableSocketHTTP.invokeServlet(Compiled Code)
 > at weblogic.socket.MuxableSocketHTTP.execute(Compiled Code)
 > at weblogic.t3.srvr.ExecuteThread.run(Compiled Code)
 >
 > "Prasad Peddada" <[email protected]> wrote in message
 > news:[email protected]...
 > > Is this causing any problems on the server. Like unable to create sessions
 > for
 > > servlets/jsp's
 > >
 > > If so, this is related to DGC bug, if not then it is something else,
 > unless we
 > > know the object it is trying to find, I can't be of much help.
 > >
 > > - Prasad
 > >
 > > Matias Pelenur wrote:
 > >
 > > > Hi,
 > > > I'm running three WL 4.5.2 servers clustered, JDK1.1.7b on Solaris 2.6.
 > > >
 > > > Normally the cluster runs just fine, but now I'm beginning to see the
 > > > following message in all three servers:
 > > >
 > > > <DGCserver> tried to renew lease for lost ref: nnn
 > > >
 > > > Usually they come in small bursts of about 5 or 10 messages that are the
 > > > same, except the "ref"s keep increasing. I'm guessing it has to do
 > something
 > > > with the in-memory replication of sessions (which I'm using).
 > > >
 > > > Any ideas? I tried restarting the servers but after a little while the
 > > > messages started again.
 > > > Thanks,
 > > >
 > > > Matias
 > >
 Cheers
 - Prasad

DGCserver

I am working with Weblogic 6.1 and testing a data access class. The data access
class calls another class, and passes it a connection. The second class is being
called many times before the first class finishes and returns a result. While
the test is running, I am getting several messages in the console as follows:
<Feb 26, 2003 9:42:38 AM MST> <Info> <DGCserver> <Tried to renew lease on lost
reference: '30869'>
I have checked to make sure that the PreparedStatements and ResultSets are closed
when no longer needed. The test eventually finishes, and returns the results.
The problem started when I added the code that calls the second class. I use the
second class in other places, and have not seen this problem before, but it isn't
called as many times as in the current test.
Any suggestions?
Thanks, Tom K

Hi Tom,
"Tom Koenning" <[email protected]> wrote in message
news:3e5e6a9d$[email protected]..
>
I am working with Weblogic 6.1 and testing a data access class. The dataaccess
class calls another class, and passes it a connection. The second class isbeing
called many times before the first class finishes and returns a result.While
the test is running, I am getting several messages in the console asfollows:
<Feb 26, 2003 9:42:38 AM MST> <Info> <DGCserver> <Tried to renew lease onlost
reference: '30869'>
I have checked to make sure that the PreparedStatements and ResultSets areclosed
when no longer needed. The test eventually finishes, and returns theresults.
The problem started when I added the code that calls the second class. Iuse the
second class in other places, and have not seen this problem before, butit isn't
called as many times as in the current test.
Any suggestions?DGCCerver stands for Distributed Garbage Collection Server. Normally
it happens when a client dies leaving RMI objects, like Connections, open.
Server tries to renew lease on such a disappeared object and gives up.
This message is harmless. AFAIR it was suppressed in 6.1 SP3.
Regards,
Slava Imeshev

DGCserver renewing lost refs

Hey all,
We're running WLS 4.5.1sp5 on solaris 2.7.
After some time, we start to see our execute queue length start to
increase dramatically. At the same time we start to see the following
messages:
Fri Jul 06 12:03:54 EDT 2001: <DGCserver> tried to renew lease for
lost ref: 677
Fri Jul 06 12:03:54 EDT 2001: <DGCserver> tried to renew lease for
lost ref: 678
Fri Jul 06 12:03:54 EDT 2001: <DGCserver> tried to renew lease for
lost ref: 692
This happens a lot and soon after start up on the new hosting
environment but hardly ever on the old hosting environment and never on
the development machines. The boxes are all the same... why would this
happen?
Any insights would be appreciated.
C.

Chad,
These messages indicate that a server got a message to renew a DGC lease for
a reference it had already collected. This means that the lease renewal
messages aren't being received and/or processed in a timely manner. Since
you mention that the execute queue length is quite long that is likely the
cause of the problem.
To diagnose that problem I would recommend taking a thread dump from the
server VM. Look at what the threads are doing. Are they blocked trying to
obtain some resource or doing some other operation that is preventing them
from proceeding?
Cheers!
Adam
"Chad Bryant" <[email protected]> wrote in message
news:[email protected]..
Hey all,
We're running WLS 4.5.1sp5 on solaris 2.7.
After some time, we start to see our execute queue length start to
increase dramatically. At the same time we start to see the following
messages:
Fri Jul 06 12:03:54 EDT 2001: <DGCserver> tried to renew lease for
lost ref: 677
Fri Jul 06 12:03:54 EDT 2001: <DGCserver> tried to renew lease for
lost ref: 678
Fri Jul 06 12:03:54 EDT 2001: <DGCserver> tried to renew lease for
lost ref: 692
This happens a lot and soon after start up on the new hosting
environment but hardly ever on the old hosting environment and never on
the development machines. The boxes are all the same... why would this
happen?
Any insights would be appreciated.
C.

DGCServer - tried to renew lease for lost ref: 509

Recently we have been getting ALOTof messages in our server log file of the
form:
Fri Jul 14 10:08:19 PDT 2000: <DGCserver> tried to renew lease for lost
ref: 509
We use RMI for java client to server communcation and are using Weblogic
4.5.1 SP 8
with nativeIO enabled.
What could be causing these messages?
Thanks!
Rick

Thanks! I still have one problem, the lease renewal messages for lost
references never seem
to end for the specific reference. I have a weblogic.log file with hundreds
of those messages for
each lost reference (and still going). It seems that it is not giving
up... any ideas?
Rick
"Michael Girdley" <[email protected]> wrote in message
news:396fa6c8$[email protected]..
Normally, I would ask a customer in the situation to provide more about
their application. But, since I know a lot about how your application is
architected, I would guess the people are shutting down their browserswhile
your applet still running. The applet is not closing the socket cleanly
with Weblogic. The distributed garbage collector, which keeps track ofall
of the distributed objects, is trying to renew a lease for that object.It
cannot locate it and will eventually give up on it.
Thanks,
Michael
Michael Girdley
Product Manager, WebLogic Server & Express
BEA Systems Inc
Rick Spickelmier <[email protected]> wrote in message
news:396f960d$[email protected]..
Recently we have been getting ALOTof messages in our server log file ofthe
form:
Fri Jul 14 10:08:19 PDT 2000: <DGCserver> tried to renew lease forlost
ref: 509
We use RMI for java client to server communcation and are using Weblogic
4.5.1 SP 8
with nativeIO enabled.
What could be causing these messages?
Thanks!
Rick

A problem with threads

I am trying to implement some kind of a server listening for requests. The listener part of the app, is a daemon thread that listens for connections and instantiates a handling daemon thread once it gets some. However, my problem is that i must be able to kill the listening thread at the user's will (say via a sto button). I have done this via the Sun's proposed way, by testing a boolean flag in the loop, which is set to false when i wish to kill the thread. The problem with this thing is the following...
Once the thread starts excecuting, it will test the flag, find it true and enter the loop. At some point it will LOCK on the server socket waiting for connection. Unless some client actually connects, it will keep on listening indefinatelly whithought ever bothering to check for the flag again (no matter how many times you set the damn thing to false).
My question is this: Is there any real, non-theoretical, applied way to stop thread in java safely?
Thank you in advance,
Lefty

This was one solution from the socket programming forum, have you tried this??
public Thread MyThread extends Thread{
     boolean active = true;
     public void run(){
          ss.setSoTimeout(90);
          while (active){
               try{
                    serverSocket = ss.accept();
               catch (SocketTimeoutException ste){
               // do nothing
     // interrupt thread
     public void deactivate(){
          active = false;
          // you gotta sleep for a time longer than the
          // accept() timeout to make sure that timeout is finished.
          try{
               sleep(91);
          }catch (InterruptedException ie){
          interrupt();
}

A problem with Threads and MMapi

I am tring to execute a class based on Game canvas.
The problem begin when I try to Play both a MIDI tone and to run an infinit Thread loop.
The MIDI tone "Stammers".
How to over come the problem?
Thanks in advance
Kobi
See Code example below:
import java.io.IOException;
import java.io.InputStream;
import javax.microedition.lcdui.Graphics;
import javax.microedition.lcdui.Image;
import javax.microedition.lcdui.game.GameCanvas;
import javax.microedition.media.Manager;
import javax.microedition.media.MediaException;
import javax.microedition.media.Player;
public class MainScreenCanvas extends GameCanvas implements Runnable {
 private MainMIDlet parent;
 private boolean mTrucking = false;
 Image imgBackgound = null;
 int imgBackgoundX = 0, imgBackgoundY = 0;
 Player player;
 public MainScreenCanvas(MainMIDlet parent)
 super(true);
 this.parent = parent;
 try
 imgBackgound = Image.createImage("/images/area03_bkg0.png");
 imgBackgoundX = this.getWidth() - imgBackgound.getWidth();
 imgBackgoundY = this.getHeight() - imgBackgound.getHeight();
 catch(Exception e)
 System.out.println(e.getMessage());
 * starts thread
 public void start()
 mTrucking = true;
 Thread t = new Thread(this);
 t.start();
 * stops thread
 public void stop()
 mTrucking = false;
 public void play()
 try
 InputStream is = getClass().getResourceAsStream("/sounds/scale.mid");
 player = Manager.createPlayer(is, "audio/midi");
 player.setLoopCount(-1);
 player.prefetch();
 player.start();
 catch(Exception e)
 System.out.println(e.getMessage());
 public void run()
 Graphics g = getGraphics();
 play();
 while (true)
 tick();
 input();
 render(g);
 * responsible for object movements
 private void tick()
 * response to key input
 private void input()
 int keyStates = getKeyStates();
 if ((keyStates & LEFT_PRESSED) != 0)
 imgBackgoundX++;
 if (imgBackgoundX > 0)
 imgBackgoundX = 0;
 if ((keyStates & RIGHT_PRESSED) != 0)
 imgBackgoundX--;
 if (imgBackgoundX < this.getWidth() - imgBackgound.getWidth())
 imgBackgoundX = this.getWidth() - imgBackgound.getWidth();
 * Responsible for the drawing
 * @param g
 private void render(Graphics g)
 g.drawImage(imgBackgound, imgBackgoundX, imgBackgoundY, Graphics.TOP | Graphics.LEFT);
 this.flushGraphics();
}

You can also try to provide a greater Priority to your player thread so that it gains the CPU time when ever it needs it and don't harm the playback.
However a loop in a Thread and that to an infinite loop is one kind of very bad programming, 'cuz the loop eats up most of your CPU time which in turn adds up more delays of the execution of other tasks (just as in your case it is the playback). By witting codes bit efficiently and planning out the architectural execution flow of the app before start writing the code helps solve these kind of issues.
You can go through [this simple tutorial|http://oreilly.com/catalog/expjava/excerpt/index.html] about Basics of Java and Threads to know more about threads.
Regds,
SD
N.B. And yes there are more articles and tutorials available but much of them targets the Java SE / EE, but if you want to read them here is [another great one straight from SUN|http://java.sun.com/docs/books/tutorial/essential/concurrency/index.html] .
Edited by: find_suvro@SDN on 7 Nov, 2008 12:00 PM

J2ME problem with threads

Hi all,
I would like to ask you for a help. I need to write a small program at my university. I started to write a midlet which function would be to countdown time for sports activities. I woul like to start a new thread - the one that counts down - and at the same time make the main thread sleep. After the "countdown" thread finishes, the main thread wakes up and waits for user input. The problem is that when the "countdown" thread finishes his work, I've got Uncaught exception java/lang/NullPointerException. error and the midlet halts.
Below you can find the code
import java.lang.*;
import java.util.*;
import javax.microedition.lcdui.*;
import javax.microedition.midlet.*;
public class intervals extends MIDlet implements CommandListener
public Display ekran;
private SweepCanvas sweeper;
private Form rundy;
private TextField round0, round1, round2, round3, round4, round5, round6, round7, round8;
private long czas,x;
private Command exitCommand;
private Command addRound;
private Command delRound;
private Command start;
private TextField repeat;
private Form odliczanie;
private Alert ostrz;
Licznik thread;
String test;
StringItem test1;
int parz,i,j,k;
static int l;
int ilrund;
int ilpowt;
Item sec;
long sec1;
public intervals()
 rundy = new Form("Interwały sportowe");
 exitCommand = new Command("Wyjście", Command.EXIT, 2);
 addRound = new Command("Dodaj","Dodaj rundę", Command.ITEM,1);
 delRound = new Command("Usuń","Usuń ostatnią rundę", Command.ITEM,1);
 start = new Command("Start", Command.ITEM,1);
 odliczanie = new Form("Odliczanie");
 TextField dodaj(TextField kolej)
 kolej=new TextField("Podaj czas (s) rundy "+parz,null, 4, TextField.NUMERIC);//stworzenie nowej instancji do wybierania czasu trwania rundy
 if(rundy.size()==0)
 rundy.insert(rundy.size(),kolej);
 else
 rundy.insert(rundy.size()-1, kolej);
 return kolej;
 void odliczanie(TextField round)
 monitor m=new monitor();
 k=Integer.parseInt(round.getString());
 ekran.setCurrent(odliczanie);
 thread=new Licznik(k,odliczanie);
 thread.start();
 ekran.setCurrent(rundy);
public void startApp()// throws MIDletStateChangeException
 rundy.deleteAll();
 repeat = new TextField("Podaj ilość powtórzeń",null,1,TextField.NUMERIC);
 rundy.addCommand(addRound);
 rundy.addCommand(exitCommand);
 rundy.setCommandListener(this);
 Canvas obrazek = new MyCanvas();
 ekran = Display.getDisplay(this);
 ekran.setCurrent(obrazek);
 czas=System.currentTimeMillis();
 while (System.currentTimeMillis()<czas+1000)
 continue;
 ekran.setCurrent(rundy);
public void pauseApp()
public void destroyApp(boolean unconditional)
 notifyDestroyed();
public void commandAction(Command c, Displayable s)
 if (c == exitCommand)
 destroyApp(false);
 notifyDestroyed();
 else if(c==addRound)
 if(rundy.size()==0)//Sprawdzenie ilości elementów w celu poprawnego wyświetlania liczby rund w formie
 parz=1;
 else
 parz=rundy.size();
 switch(parz)
 case 1:
 round0=dodaj(round0);break;
 case 2:
 round1=dodaj(round1);break;
 case 3:
 round2= dodaj(round2);break;
 case 4:
 round3=dodaj(round3);break;
 case 5:
 round4=dodaj(round4);break;
 default:
 ostrz=new Alert("Uwaga","Maksymalna liczba rund wynosi 9", null, AlertType.INFO);
 ostrz.setTimeout(3000);
 ekran.setCurrent(ostrz);
 if(rundy.size()==1)
 rundy.append(repeat);
 rundy.addCommand(start);
 rundy.addCommand(delRound);
 else if(c==delRound)
 if(rundy.size()!=0)
 rundy.delete(rundy.size()-2);
 if (rundy.size()==1)
 rundy.deleteAll();
 if(rundy.size()==0)
 rundy.removeCommand(delRound);
 rundy.removeCommand(start);
 else if(c==start)
 ilrund=rundy.size()-1;
 if(this.repeat.size()>0)
 ilpowt=Integer.parseInt(this.repeat.getString());
 ekran = Display.getDisplay(this);
 for (i=1; i<=ilpowt;i++)
 odliczanie= new Form("Odliczanie");
 for (j=0;j<ilrund;j++)
 switch(j)
 case 0:
 odliczanie(round0);
 break;
 case 1:
 odliczanie(round1);
 break;
 case 2:
 odliczanie(round2);
 break;
 case 3:
 odliczanie(round3);
 break;
 case 4:
 odliczanie(round4);
 break;
 case 5:
 odliczanie(round5);
 break;
 case 6:
 odliczanie(round6);
 break;
 case 7:
 odliczanie(round7);
 break;
 case 8:
 odliczanie(round8);
 break;
class Licznik extends Thread
 int czas1,k;
 Form forma;
 monitor m;
 public Licznik(int k,Form formap)
 czas1=k;
 forma=formap;
 public synchronized void run()
 while(czas1>0)
 forma.deleteAll();
 forma.append("Czas pozostały (s): "+czas1);
 try{Thread.sleep(1000);} catch(InterruptedException e){e.printStackTrace();}
 czas1--;
 if(czas1<=0)
 m.put();
 }and monitor class
public class monitor
boolean busy=false;
synchronized void get()
 if(!busy)
 try
 wait();
 }catch(InterruptedException e){e.printStackTrace();}
 notify();
synchronized void put()
 if(busy)
 try
 wait();
 }catch(InterruptedException e){e.printStackTrace();}
 busy=true;
 notify();
}Can anybody help me with this?

Groovemaker,
Your Licznik class has a member m of type monitor, which has not been instantiated (in other words is null) hence, when calling m.put() you get NullPointerException. Please also mind, that using Thread.sleep(1000) is not an accurate way of measuring time.
If I may, please use recommended for Java class naming conventions - some of your names use lower case, while other don't which is confusing to the reader.
Daniel

Problem with threads within applet

Hello,
I got an applet, inside this applet I have a singleton, inside this singleton I have a thread.
this thread is running in endless loop.
he is doing something and go to sleep on and on.
the problem is,
when I refresh my IE6 browser I see more than 1 thread.
for debug matter, I did the following things:
inside the thread, sysout every time he goes to sleep.
sysout in the singleton constructor.
sysout in the singleton destructor.
the output goes like this:
when refresh the page, the singleton constructor loading but not every refresh, sometimes I see the constructor output and sometimes I dont.
The thread inside the singleton is giving me the same output, sometime I see more than one thread at a time and sometimes I dont.
The destructor never works (no output there).
I don't understand what is going on.
someone can please shed some light?
thanks.
btw. I am working with JRE 1.1
this is very old and big applet and I can't convert it to something new.

Ooops. sorry!
I did.
     public void start() {
     public void stop() {
     public void destroy() {
          try {
               resetAll();
               Configuration.closeConnection();
               QuoteItem.closeConnection();
          } finally {
               try {
                    super.finalize();
               } catch (Throwable e) {
                    e.printStackTrace();
     }

Problem with Threads and a static variable

I have a problem with the code below. I am yet to make sure that I understand the problem. Correct me if I am wrong please.
Code functionality:
A timer calls SetState every second. It sets the state and sets boolean variable "changed" to true. Then notifies a main process thread to check if the state changed to send a message.
The problem as far I understand is:
Assume the timer Thread calls SetState twice before the main process Thread runs. As a result, "changed" is set to true twice. However, since the main process is blocked twice during the two calls to SetState, when it runs it would have the two SetState timer threads blocked on its synchronized body. It will pass the first one, send the message and set "changed" to false since it was true. Now, it will pass the second thread, but here is the problem, "changed" is already set to false. As a result, it won't send the message even though it is supposed to.
Would you please let me know if my understanding is correct? If so, what would you propose to resolve the problem? Should I call wait some other or should I notify in a different way?
Thanks,
B.D.
Code:
private static volatile boolean bChanged = false;
private static Thread objMainProcess;
   protected static void Init(){
        objMainProcess = new Thread() {
            public void run() {
                while( objMainProcess == Thread.currentThread() ) {
                   GetState();
        objMainProcess.setDaemon( true );
        objMainProcess.start();
    public static void initStatusTimer(){
        if(objTimer == null)
             objTimer = new javax.swing.Timer( 1000, new java.awt.event.ActionListener(){
                public void actionPerformed( java.awt.event.ActionEvent evt){
                          SetState();
    private static void SetState(){
        if( objMainProcess == null ) return;
        synchronized( objMainProcess ) {
            bChanged = true;
            try{
                objMainProcess.notify();
            }catch( IllegalMonitorStateException e ) {}
    private static boolean GetState() {
        if( objMainProcess == null ) return false;
        synchronized( objMainProcess ) {
            if( bChanged) {
                SendMessage();
                bChanged = false;
                return true;
            try {
                objMainProcess.wait();
            }catch( InterruptedException e ) {}
            return false;
    }

Thanks DrClap for your reply. Everything you said is right. It is not easy to make them alternate since SetState() could be called from different places where the state could be anything else but a status message. Like a GREETING message for example. It is a handshaking message but not a status message.
Again as you said, There is a reason I can't call sendMessage() inside setState().
The only way I was able to do it is by having a counter of the number of notifies that have been called. Every time notify() is called a counter is incremented. Now instead of just checking if "changed" flag is true, I also check if notify counter is greater than zero. If both true, I send the message. If "changed" flag is false, I check again if the notify counter is greater than zero, I send the message. This way it works, but it is kind of a patch than a good design fix. I am yet to find a good solution.
Thanks,
B.D.

Problem with threads running javaw

Hi,
Having a problem with multi thread programming using client server sockets. The program works find when starting the the application in a console using java muti.java , but when using javaw multi.java the program doesnt die and have to kill it in the task manager. The program doesnt display any of my gui error messages either when the server disconnect the client. all works find in a console. any advice on this as I havent been able to understand why this is happening? any comment would be appreciated.
troy.

troy,
Try and post a minimum code sample of your app which
does not work.
When using javaw, make sure you redirect the standard
error and standard output streams to file.
Graeme.Hi Graeme,
I dont understand what you mean by redirection to file? some of my code below.
The code works fine under a console, code is supposed to exit when the client (the other server )disconnects. the problem is that but the clientworker side of the code still works. which under console it doesnt.
public class Server{
ServerSocket aServerSocket;
Socket dianosticsSocket;
Socket nPortExpress;
ClientListener aClientListener;
LinkedList queue = new LinkedList();
int port = 0;
int clientPort = 0;
String clientName = null;
boolean serverAlive = true;
* Server constructor generates a server
* Socket and then starts a client threads.
* @param aPort      socket port of local machine.
public Server(int aPort, String aClientName, int aClientPort){
port = aPort;
clientName = aClientName;
clientPort = aClientPort;
try{
// create a new thread
aServerSocket = new ServerSocket(port) ;
// connect to the nPortExpress
aClientListener = new ClientListener(InetAddress.getByName(clientName), clientPort, queue,this);
// aClientListener.setDaemon(true);
aClientListener.start();
// start a dianostic port
DiagnosticsServer aDiagnosticsServer = new DiagnosticsServer(port,queue,aClientListener);
// System.out.println("Server is running on port " + port + "...");
// System.out.println("Connect to nPort");
catch(Exception e)
// System.out.println("ERROR: Server port " + port + " not available");
JOptionPane.showMessageDialog(null, (e.toString()),"ERROR: Server port " + port + " not available", JOptionPane.ERROR_MESSAGE);
serverAlive = false;
System.exit(1);
while(serverAlive&&aClientListener.hostSocket.isConnected()){
try{
// connect the client
Socket aClient = aServerSocket.accept();
//System.out.println("open client connection");
//System.out.println("client local: "+ aClient.getLocalAddress().toString());
// System.out.println("client localport: "+ aClient.getLocalPort());
// System.out.println("client : "+ aClient.getInetAddress().toString());
// System.out.println("client port: "+ aClient.getLocalPort());
// make a new client thread
ClientWorker clientThread = new ClientWorker(aClient, queue, aClientListener, false);
// start thread
clientThread.start();
catch(Exception e)
//System.out.println("ERROR: Client connection failure");
JOptionPane.showMessageDialog(null, (e.toString()),"ERROR: Client connection failure", JOptionPane.ERROR_MESSAGE);
}// end while
} // end constructor Server
void serverExit(){
     JOptionPane.showMessageDialog(null, "Server ","ERROR: nPort Failure", JOptionPane.ERROR_MESSAGE);
     System.exit(1);
}// end class Server
*** connect to another server
public class ClientListener extends Thread{
InetAddress hostName;
int hostPort;
Socket hostSocket;
BufferedReader in;
PrintWriter out;
boolean loggedIn;
LinkedList queue;      // reference to Server queue
Server serverRef; // reference to main server
* ClientListener connects to the host server.
* @param aHostName is the name of the host eg server name or IP address.
* @param aHostPort is a port number of the host.
* @param aLoginName is the users login name.
public ClientListener(InetAddress aHostName, int aHostPort,LinkedList aQueue,Server aServer)      // reference to Server queue)
hostName = aHostName;
hostPort = aHostPort;
queue = aQueue;
serverRef = aServer;
// connect to the server
try{
hostSocket = new Socket(hostName, hostPort);
catch(IOException e){
//System.out.println("ERROR: Connection Host Failed");
JOptionPane.showMessageDialog(null, (e.toString()),"ERROR: Connection to nPort Failed", JOptionPane.ERROR_MESSAGE);
System.exit(0);
} // end constructor ClientListener
** multi client connection server
ClientWorker(Socket aSocket,LinkedList aQueue, ClientListener aClientListener, boolean diagnostics){
queue = aQueue;
addToQueue(this);
client = aSocket;
clientRef = aClientListener;
aDiagnostic = diagnostics;
} // end constructor ClientWorker
* run method is the main loop of the server program
* in change of handle new client connection as well
* as handle all messages and errors.
public void run(){
boolean alive = true;
String aSubString = "";
in = null;
out = null;
loginName = "";
loggedIn = false;
while (alive && client.isConnected()&& clientRef.hostSocket.isConnected()){
try{
in = new BufferedReader(new InputStreamReader(client.getInputStream()));
out = new PrintWriter(new OutputStreamWriter(client.getOutputStream()));
if(aDiagnostic){
out.println("WELCOME to diagnostics");
broadCastDia("Connect : diagnostics "+client.getInetAddress().toString());
out.flush();
else {
out.println("WELCOME to Troy's Server");
broadCastDia("Connect : client "+client.getInetAddress().toString());
     out.flush();
String line;
while(((line = in.readLine())!= null)){
StringTokenizer aStringToken = new StringTokenizer(line, " ");
if(!aDiagnostic){
broadCastDia(line);
clientRef.sendMessage(line); // send mesage out to netExpress
out.println(line);
out.flush();
else{
if(line.equals("GETIPS"))
getIPs();
else{
clientRef.sendMessage(line); // send mesage out to netExpress
out.println(line);
out.flush();
} // end while
catch(Exception e){
// System.out.println("ERROR:Client Connection reset");
                         JOptionPane.showMessageDialog(null, (e.toString()),"ERROR:Client Connection reset", JOptionPane.ERROR_MESSAGE);
try{
if(aDiagnostic){
broadCastDia("Disconnect : diagnostics "+client.getInetAddress().toString());
out.flush();
else {
broadCastDia("Disconnect : client "+client.getInetAddress().toString());
     out.flush();
// close the buffers and connection;
in.close();
out.close();
client.close();
// System.out.println("out");
// remove from list
removeThreadQueue(this);
alive = false;
catch(Exception e){
// System.out.println("ERROR: Client Connection reset failure");
JOptionPane.showMessageDialog(null, (e.toString()),"ERROR: Client Connection reset failure", JOptionPane.ERROR_MESSAGE);
}// end while
} // end method run
* method run - Generates io stream for communicating with the server and
* starts the client gui. Run also parses the input commands from the server.
public void run(){
boolean alive = true;
try{
// begin to life the gui
// aGuiClient = new ClientGui(hostName.getHostName(), hostPort, loginName, this);
// aGuiClient.show();
in = new BufferedReader(new InputStreamReader(hostSocket.getInputStream()));
out = new PrintWriter(new OutputStreamWriter(hostSocket.getOutputStream()));
while (alive && hostSocket.isConnected()){
String line;
while(((line = in.readLine())!= null)){
System.out.println(line);
broadCast(line);
} // end while
} // end while
catch(Exception e){
//     System.out.println("ERRORa Connection to host reset");
JOptionPane.showMessageDialog(null, (e.toString()),"ERROR: Connection to nPort reset", JOptionPane.ERROR_MESSAGE);
try{
hostSocket.close();
     }catch(Exception a){
     JOptionPane.showMessageDialog(null, (a.toString()),"ERROR: Exception", JOptionPane.ERROR_MESSAGE);
alive = false;
System.exit(1);
} // end method run

Problem with Threads and "plase wait..."-Window

Hi everyone,
I have a problem that I'm not able to solve in any way... I have a time-consuming task (a file decryption) which I execute in a separate thread; I've used the SwingWorker class, like suggested by sun-tutorial, and it works right. The problem is that I have to wait that the decryption have finished before continuing with program-execution. Therefore I would like to display a "please wait"-window while the task runs. I've tryed all the possible ways I know but the problem is always the same: the waitWindow is displayed empty, the bounds are painted but the contents no; it's only painted when the decrypt-task has finished. Please help me, I have no more resources....
decrypt-file code:
public class DecryptFile {
private String cryptedFileNameAndPath;
private ByteArrayInputStream resultStream = null;
// need for progress
private int lengthOfTask;
private int current = -1;
private String statMessage;
public DecryptFile(String encZipFileNameAndPath) {
    cryptedFileNameAndPath = encZipFileNameAndPath;
    //Compute length of task...
    // 0 for indeterminate
    lengthOfTask = 0;
public ByteArrayInputStream getDecryptedInputStream() {
    return this.resultStream;
   * Called from ProgressBarDemo to start the task.
public void go() {
    current = -1;
    final SwingWorker worker = new SwingWorker() {
      public Object construct() {
        return new ActualTask();
    worker.start();
   * Called from ProgressBarDemo to find out how much work needs
   * to be done.
public int getLengthOfTask() {
    return lengthOfTask;
   * Called from ProgressBarDemo to find out how much has been done.
public int getCurrent() {
    return current;
public void stop() {
    current = lengthOfTask;
   * Called from ProgressBarDemo to find out if the task has completed.
public boolean done() {
    if (current >= lengthOfTask)
      return true;
    else
      return false;
public String getMessage() {
    return statMessage;
   * The actual long running task. This runs in a SwingWorker thread.
class ActualTask {
    ActualTask () {
      current = -1;
      statMessage = "";
      resultStream = AIUtil.getInputStreamFromEncZip(cryptedFileNameAndPath); //here the decryption happens
      current = 0;
      statMessage = "";
}The code that calls decryption and displays waitWindow
      final WaitSplash wS = new WaitSplash("Please wait...");
      final DecryptFile cryptedTemplate = new DecryptFile (this.templateFile);
      cryptedTemplate.go();
      while (! cryptedTemplate.done()) {
        try {
          wait();
        } catch (Exception e) { }
      this.templateInputStream = cryptedTemplate.getDecryptedInputStream();
      wS.close();Thanks, thanks, thanks in advance!
Edoardo

Maybe you can try setting the priority of the long-running thread to be lower? so that the UI will be more responsive...

Problem with threads in j2me

im using jdk 1.6 with java wtk 2.1
ya i know..
2.1 is a jdk1.4 source
but im using souce as 1.4 during compiliation so thats not the prob
this is my code
package org.learn;
import javax.microedition.midlet.MIDlet;
import javax.microedition.lcdui.Alert;
import javax.microedition.lcdui.Display;
public class thtest extends MIDlet
Thread t;
public void startApp()
Alert a=new Alert("hello");
a.setString("hello");
Alert b=new Alert("world");
b.setString("world");
Display d = Display.getDisplay(this );
d.setCurrent(a);
t=Thread.currentThread();
try{
t.sleep(10000);
catch (Exception e){}
d.setCurrent(b);
public void pauseApp()
public void destroyApp(boolean unconditional)
its just supposed to pause between the alerts using threads
however when i run it using the wtk, the emulator run properly but when i launch the app, it stops executing giving me this:
"Error verifying method org/learn/thtest startApp()V
Approximate bytecode offset 49: Inconsistent or missing stackmap at target
%the stack info%
Execution completed.
437782 bytecodes executed
9 thread switches
486 classes in the system (including system classes)
2506 dynamic objects allocated (73832 bytes)
2 garbage collections (60652 bytes collected)
Execution completed.
437782 bytecodes executed
9 thread switches
486 classes in the system (including system classes)
ALERT: java/lang/VerifyError: org/learn/thtest.
2506 dynamic objects allocated (73832 bytes)
2 garbage collections (60652 bytes collected)
please can someone help me out with this, is it an error on my part or do i have to set some option.

Hi gandalf123,
First, Thread.sleep is a static method, so you don't need to create a Thread object to use it.
I think the problem is due to the fact you don't preverify your midlet.
More over, you don't need to double post your question.

Problem with threads and camera.

Hi everybody!
I've a problem with taking snapshot.
I would like to display a loading screen after it take snapshot ( sometimes i
have to wait few seconds after i took snapshot. Propably photo is being taken in time where i have to wait).
I was trying to use threads but i didn't succeed.
I made this code:
display.setCurrent(perform);
        new Thread(new Runnable(){
            public void run() {
                while((!performing.isShown()) && (backgroundCamera.isShown())){
                    Thread.yield();
                notifyAll();
        }).start();
        new Thread(new Runnable(){
            public void run() {
                try {
                    this.wait();
                } catch(Exception e) {
                    exceptionHandler(e);
                photo = camera.snapshot();
                display.setCurrent(displayPhoto);
        }).start();This code is sometimes showing performing screen but sometimes no.
I don't know why. In my opinion performing.isShown() method isn't working correctly.
Does anyone have some idea how to use threads here?

Hi,
I've finally managed to work this fine.
The code:
       Object o = new Object();
       display.setCurrent(perform);
        new Thread(new Runnable(){
            public void run() {
                while(!performing.isShown()){
                    Thread.yield();
               synchronized(o) {
                  o.notify();
        }).start();
        new Thread(new Runnable(){
            public void run() {
                try {
                    synchronized(o) {
                       o.wait(1);
                } catch(Exception e) {
                    exceptionHandler(e);
                photo = camera.snapshot();
                display.setCurrent(displayPhoto);
        }).start();

DGCserver problem.......

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