Applet OK on Windows XP, WRONG on Windows 7 - Java Applet Development

I've an applet that has been running for a while. I have Tomcat 6.0 as webserver. My problem is that my applet works great on Windows XP, but it don't run at all on Windows 7. The exception in 7 says that it can find some class, but no problem in XP. I've an executable .jar file, that installs some libraries in the JRE of the client. In XP I just double-click the .jar file and that's it, everything is installed OK. In 7, it doesn't execute with double-click, so I opened a cmd as administrator and ran the file with a java -jar command, the installation message said everything went OK. When checking the directories in the JRE, the files ARE there, exactly in the same directories as in XP, but it doesn't execute, it just continues to throw an exception telling that it can find a class.
My question is, why if both Windows have exactly the same things (same webserver, same JDK version, same WAR project, same installation of additional libraries in the same folders of the virtual machine) the applet runs fine without a problem in XP but it doesn't in 7? Does 7 blocks some parts due to the different "security" approach (asking you about everything)?
I of course have deactivated the firewall, antivirus, antispam, antiwhatever, but it just doesn't execute on 7. Same version of IE. I'have tried to test it in FireFox with the same results, OK on XP, Wrong on 7 (class not found).
I'm not sure, but I believe is exactly the same in Vista, than is in 7. I remember some years ago that I had a similar problem on Vista, but just switched back to XP (not an option right now)
Any idea out there?
Best regards,

Laerion wrote:
..Any idea out there?- Post a lot more detail about the error..
..The exception in 7 says that it can find some class, ....always [copy/paste error messages|] *(<- link).*
- Make sure the code is not [swallowing exceptions|] *(<- link).*
- Quote the exact JREs being used (make and model) and the exact browsers (make & model).
- Validate the HTML
- Is the applet publicly available, small & sand-boxed? Post the URL where we can visit it. Failing that..
- Copy/paste the applet element or object/embed element or JavaScript attributes that launch the applet.


help! Java no longer works with IE or Firefox

This all started when I downloaded JRE ...whatever the latest version is. Java was working fine in both browsers. Then I installed JRE so I could run some Java program (which works fine), but now, it doesn't work in the Internet browsers. I tried uninstalling and reinstalling but still it doesn't work.
Help is appreciated! A lot of basic websites are useless without it. Thanks 
What is now installed? Give the Java version and the exact name of the directories stuff is in. You may have only installed the SDK, not the JRE.
Also - is there a Java entry in the Windows Control Panel? 
C:\Program Files\Java\jre1.5.0_01
That's the directory in the Java folder. And I do have Java in the Windows Control Panel. The weird thing is that Java was working fine in my browsers up til the day I installed JRE. Makes me guess that's the cause somehow. Didn't do anything else out of the ordinary. 
I faced the same problem ...To fix this you can try this.Uninstall the JRE/SDK .Remove the registry entries under HKEY_LOCAL_MACHINE\SOFTWARE\JavaSoft .And then reinstall the JRE/SDK .
This problem seems to occur if you install the SDK with out the JRE initially and then later try to install the JRE .. For FireFox ..remove the java plugins from the plugins dir before you reinstall..And make sure you close all applications that can possibly use java before you reinstall
I have posted a question that is kinda related to this question
Appreciate if any one could answer this 
Thanks, but it's still not working. When I reopened firefox and took it to a Java page, it told me I needed to install a plugin for that page. I said okay, and it automatically started a Java plugin installer. Then a window popped up saying JRE's already installed so it couldn't do anything. 
Open the Windows Control Panel, there should be a Java entry. Open it and click the Java tab | Applet Runtime Settings | View, and verify that it shows the 1.5.0_01 JRE.
Then click the Advanced tab | "<APPLET> tag support"; Internet Explorer should be checked. If it's not, check it.
Open the IE Tools menu, there should be a Sun Java Console entry. If it's there, click it - it should open the Java Console, showing version 1.5.0_01.
At this point, IE should work. FF problems are a matter of FF settings, I can't help.
If after this IE isn't working, then Java is trashed, removal of Java and reinstall is probably needed. It may be necessary to manually clean the Registry. If there are multiple versions, remove them all. Reinstall 1.5.0_01 last. 
Unbelievable...I unistalled everything Java on my computer, ran a registry cleaner program and reinstalled, and the problem is still there. Guess it'll take a new reinstall of Windows to work :( 
thanks everybody, for the help though/ 
try reinstallation after removing the plugin dlls (e.g NPJPI_xxxx.dll(xxxx is the version of the JRE)) it is usually found in the FireFox plugins path.But its possible that it is installed elsewhere too...(JSDK likes to spit these files in different files) might have to do a "regsvr32 /u" on the dll before you delete it .. 
Okay, but what does "regsvr32 /u" mean? 
It mean you uneregister the dll to say it is not used anymore by any program. 
Solved! The solution is really weird...
Java wouldn't work with Firefox OR Internet Explorer, even after all those reinstalls and registry entry deletions.
Then yesterday, I upgraded Firefox from 1.0 to 1.0.1, and all of a sudden Java works fine with Firefox AND Internet Explorer! 
Stumbling around not knowing what you're doing is not a "solution". 
Well, however the problem got solved, I'm just happy it's gone. Much thanks to everyone who helped!

SDK 1.4.1 and Redhat 8

Okay then...
I'm running Redhat 8 and Netscape 4.75 and I'd like to run the J2 sdk v1.4.1.
I have it installed and it will happily compile, it will run command line applications. The problem is it won't run applets, or anything with a GUI. They will compile but when it comes to running.....not a chance
I have the plug-in installed on netscape. And am using the 'demo' applets supplied from Sun with the sdk to test this function.
If I try to run the applet one of two things happens.
1) By double clicking in the file manager it launches mozilla (which also has the plug-in) the window comes up with the html presented and an icon on the screen that represents the applet, when I click on the applet I get a error message " This page contains information of a type (applicatio/x-java-vm) that can only be view with the appropriatwe plug-in"
2) I open the file via Netscape ( File -> Open Page -> Choose File etc etc) and the html page pops up with the message " java.lang.ClassFormatError - Bad major version number" along the bottom of the screen.
3) I use the command prompt (java MyApplet) and I get a hole host of errors, mainly to do with class Lang... but others also.... there's too many to metion here...
So then a few questions arise.... why doesn't the plug-in work... and why don't applets work at all??? I use the applets on the java.sun tutorial pages and they come up without a problem.... unless I take the code which doesn't compile and doesn't run... most odd.
Anyway, I'm completely out of ideas and all and any help is greatly appreciated.... HAS ANYONE ELSE EXPERIENCED THIS...
Actually I have sonce removed the SDK and replaced ut with the run time environment, the same thing happens.
First Make sure JDK 1.4.1(SDK 1.4.1) will Support RedHat Linux 8.
Please reffer the Release notes. I hope JDK 1.4.1 does not support RedHat Linux 8
It doesn't mention it. It only mentions versions upto 7.1
But as RH8 was only released a few eeks ago this could be due to the file being outdated. I've searched for this information but have not found any.
does anyone out there know if j2sdk1.4.1 does support RH8?? 
I don't think that 1.4 supports the Netscape version you're using. Sorry to say, but NS 4.75 is dead and gone. I'm running 1.4 and Mozilla 1.1 (RPM on that one, binary on the JDK) with no problem. And I haven't tweaked any of the core RH system that would impact using the JDK (No! Really! At least not yet!).
Just use the rpm that Sun provides, it's acutally an rpm wrapped in a script rpm.bin. I agree that your version of Netscape is ancient. It might even be causeing conflicts with Mozilla 1.1 that comes with RH 8.0. It all works, just follow the steps carefully in the other post.
I'm not sure if your system is messed up now though with all the installing and whatnot. I'd trash Netscape 4 if I were you. Use Galeon.
Mozilla is actually derived from Netscape. The current Mozilla that comes with RH8.0 is related to Netscape 6.1. 
...and Galeon uses Mozilla's plugins. 
You've got the Netscape/Mozilla relationship backwards: Netscape 7 is Mozilla 1. 
Mozilla now works and Netscape is tempremental..
although files still won't compile if they use awt or swing for a whole host of reasons which I'm yet to fathom...
Thanks for the help..
Hello, thought I 'ought to fill you in....
Basically I couldn't get the SDK to work on my Red Hat box and so I've swapped machines and am back on Windows. Now everything is perky and it installed first time...
I had tried just about everything with Red Hat, about 8 different downloads, 3 clean OS installs and even two seperate 'one click wonder' developer suites. But alas it just wouldn't work, and I have absolutely no idea why.
But thanks for the help anyway, (and speedy replies), at least now I know more about unix!!
try setting the environment variable LD_ASSUME_KERNEL="2.2.5"
Would sreeni ananth let us know iif
LD_ASSUME_KERNEL is the only environment variable to set.
I got the same problem as Adam had, when I run
applet on Red hat 8.0, I got exception the Listener class
return type is incompatiable.
I also add to lib
prior to about error that so I did not get any run time
error from gnu which starts my java applet.
Thank you a bunch.
The java 1.4.1_02 works on Windows after it installed without any hitch. 
I got some of my answer in the following web page
The problem I ran into was when I installed Redhat 8.0 with every
package, the /usr/bin/java is in 1.3.1 and it was not compatiable
with even jdk1.3.1_07, and of course j2sdk1.4.1_02 because
many changes to javax.swing went in.
The about web page suggested to create the file /etc/profile.d/
to include PATH=/usr/java/j2sdk1.4.1_02/bin:$PATH.
I also installed from javax.comm.api
package in /usr/java/j2sdk1.4.1_02/jre/lib directory
to get rid of the run time error from GNU that invokes
java applet.
If anyone is interesting to run applet or web application that
needs special fonts other than Enlish, please download
fonts to /usr/java/j2sdk1.4.1_02/jre/fonts directory.
I just installed some Chinese tru type fonts (.ttf) in that
directory and am able display Chinese character with
given encoding. You have to tell for example JTextArea what
font you want to display and FileInputStream for example
what encoding you want to use in your java code.
In Windows, every thing work right after I downloads the jdk
I do not need to do anything special because my Window 2000
and Window XP already have Chinese fonts I need. I also
use Textpad to code, compile and run my java application and
applet. Textpad is a nice tool on Window environment
that color code Java program key words and you can double
click compiling error and get to the error right away.
Hope this info help.

Java JRE (1.4.2) - doesn't work on 2000 server ???

Installed Java JRE 1.4.2 on Windows 2000 server (with SP4 etc). Anyway, I've got an app that uses Java and this part doesn't work at all. It seems to pop up a windows temporarily and then nothing happens.
How can I troubleshoot Java? Is there any way I can test the
installation to see if Java is working?
I've previously got this all working on Windows 2000 Pro, but now I'm
trying 2000 server.
(BTW. Yes, I know theres a later version of Java JRE but for various
reasons we have to use v1.4.2). 
Installed Java JRE 1.4.2 on Windows 2000 server (with
SP4 etc). Anyway, I've got an app that uses Java and
this part doesn't work at all. It seems to pop up a
windows temporarily and then nothing happens. One's got to love these error descriptions.
How can I troubleshoot Java? Is there any way I can
test the
installation to see if Java is working? Type "java -version" at the command prompt. Pretty good sign that it was installed okay. 
Hey, I call it like I see it :-) 
blame the application, not Java ;)
If it's a Java application the simple fact that you get a popup means the JRE is working. 
blame the application, not Java ;)
If it's a Java application the simple fact that you
get a popup means the JRE is working.Not neccessarily. It could be they are double clicking a batch file which opens a cmd window discovers no JRE present and aborts. 
possibly, but then I'd expect them to have found that out by running the batchfile from a commandprompt before complaining that "Java doesn't work" ;)
And of course I assumed that they indeed have Java installed and running, as they seem confident of which version they're using.

JDK 1.3.1_01a installs incorrectly.

I installed the last update of 1.3.1_01a.
The installation step seems OK.
I choose the default directory.
But, when I try to launch an applet from within IE, it complains that roughly (translating from french):
"Unable to load Java execution environment from <����\bin\hotspot\jvm.dll>"
I presume this is a little problem with PATH environment variables or something. But I know nothing about Windows.
Any help is welcome 
Do keep in mind that IE uses it's own version of Java. The one you installed has nothing to do with IE.
Sounds like you may have an Internut Exploder problem. :o) Try upgrading your version of Internet Explorer.

Going round in circles trying to deploy my application

About 2 weeks ago I put my demonstration program onto my website and it worked, at least on my m/cs. I am using Netbeans. I am now not sure what versions of Java and FX I used at that time. I have a problem (on another thread) where it was suggested things might work with FX2.2. It didn't help and I am now using Java 1.7.0_5 and FX2.1
In my dist folder there are 3 files. If I click on .jar, the system works. If I click of .jnlp, the system works. If I click on .html, a webpage comes up offering me 2 choices, 1 to launch my program using webstart, the other to Instal Java. If I click on either, I am taken to the Java download page which eventually tells me that I already have the latest version of Java installed.
Any ideas on what I am doing wrong?
As soon as you go the "html" way, you move the problem domain to a web browser. In all other cases that you run your application its just the local JVM that is picking stuff up.
So yeah. If what I say is true, apparently you are missing the browser plugin required. Are you trying to run this through internet explorer? If so I would make sure that you are running the version of IE that matches the java runtime you have installed (so if you have a 64 bits java runtime, make sure that the 64 bits version of internet explorer is opened to 'run' the html file). 
Hi Gimbal2
You are right about it being something to do with the browser instructions but it is not the plug-in. I have IE, Firefox and Chrome on my m/c. The file works ok in IE but not the other 2. All 3 use the same plugin - SE7U5 Updated May 2012.
I get the same behaviour if I try to run by demonstration from my website - again it was working last week before I changed it yesterday with the new version.
You can try it at [eco-wand demonstration|]
The above is the behavior on my development m/c - Win XP
I also have a demonstration m/c - Win Vista. The download behavior of the demonstration program is different on it. On both IE and Chrome, the program starts to load but freezes after 5% has been loaded.
This has all been happening since I upgraded to 1.7.0_5
Hope you can help
trying to get the link to be active - don't think I have suceeded
[eco-wand demonstration|]
Edited by: abg on 29-Jun-2012 06:42 
abg wrote:
Hope you can helpSorry, no. I'm just a lonely programmer like you, technical issues are not something I can debug. The only thing I can do is repeat what I've read before on this site, and I'm coming up blank.
trying to get the link to be active - don't think I have suceededJust post the URL as plain text without any button or tag and the forum will turn it into a link. I have seen people create a named url by putting a HTML a href tag. Let me try that.
Oracle Website
EDIT: yep, that works :) 
I'm still going round in circles. My version checker aplet says I have Java 1.7.0_5, Java Console says I've got Java1.7.0_5 but my FX applet doesn't see it. When I click to install, Java installer says I've got it. What am I missing?
On my XP m/c, it was working last week on IE, Firefox and Chrome. This week it only works in IE. I have cleared the cache, uninstalled java and reinstalled. I have uninstalled 1.7.0_5 and installed 1.7.0_4 ( I think that is what I was using when it did work). I have now re-installed 1.7.0_5. Nothing seems to make any difference. I have tried to check Firefox plug in - it seems ok but I can't see how to check Chrome pluug-in.
The problem has now spread to my Vista m/c - it was acting differently when the JRE was 1.7.0_5 and the JDK was 1.7.0_3. The JDK has now been updated to 1.7.0_5
This is holding back the deployment of my application.
<a ref = '' </a>
If anyon tries the link, please let me know your experience at
It sounds like there is a plugin registration issue.
What browser are you using? Is it the same behavior for both browsers?
What you have installed? Screenshot from list of installed programs may be useful.
JDK is not relevant for web deployment. Look for Java Runtime and JavaFX Runtime.
Open list installed plugins (e.g. type about:plugins in the location bar for FF and Chrome).
You should have ONE java plugin there and ONE Deployment Toolkit plugin. Both enabled.
Please post versions (or better screenshot) here.
Use Process Explorer from to see what Oracle dlls are loaded into browser process. Please report them and their versions here.
Things that may help you to clean up the system:
- install FX 2.1.1, every time you update JRE you need to update JavaFX
(this will be easier starting 7u6 once JavaFX will be part of JRE)
- install latest 7u6 build from
If you are willing to help to fix this issue - please file a JIRA to
It will make it easier to collect troubleshooting data and in the end we will make JavaFX more robust (not just resolve this in your environment) 
Hi Igor
Thanks for the reply. Looking at it closely with the help of Process Explorer, I don't think it is a plugin problem. In IE8 which works, you can see that java.exe is being used. In FF 13.0.1 and Chrome 20.0.1132.47 ( which do not work) java.exe is not shown. This suggest to me that the problem is with the jnlp call in the html program generated by Netbeans. When I load a program with a standard java applet, java.exe is accessed by the browsers.
I have loaded Java1.7.0_6 and the programs work in all browsers with this jre.
Do you know when version _6 will become the standad version? As it stands, my visitors will be updated to _5 when they try to access my program.