Java ClassNotFoundException

[Phil_the_Power]

Hi Everybody,

 

We're getting lots of Windows 7 machines with these kind of Java errors. Whatever the applet is, a "java.lang.ClassNotFoundException" error happens. For example, when trying the Java Verify from the website, the error reads: java.lang.ClassNotFoundException: jreCheck.class

 

I've been through the Java help and made sure that it's turned on, I've uninstalled and re-installed with assorted restarts in between. Even searching through ProgramData and the local profile and deleting everything to do with Sun/Java didn't get it working.

 

Does anyone have more of a clue that I do, because I'm making this look difficult?

[Michael]

Are you running Windows 7 32Bit or 64Bit and what version of Java are you using? Is it an application or a website you require that uses Java?

[Phil_the_Power]

It's Windows 7 32 bit. I've tried a variety of Java versions from 6 update 29 to update 31 (just seen a newer version to try!)

 

It doesn't seem to matter whether it's an application or a website, neither work. I get the impression that something isn't installing correctly. I'm in the process of re-installing a PC and starting from there, trying to see if something breaks it.

[Michael]

It could well be something registry related if it affects both applications and websites. I presume other plugins such as Flash are working OK?

[Phil_the_Power]

All other plugins appear to be fine. Or at least we haven't found anything else yet!

[Sandman]

Try the following steps:

 

 

Welcome to Microsoft answers

1. Remove all the Java plug in from the computer.

 

2. Remove it from programs and features

 

(check this link to remove Java - How do I uninstall Java on my Windows computer ? )

 

3. Later download the latest version of Java and install it.

 

(Refer this link to download and install - Java Downloads for All Operating Systems )

 

4. On the same window, you find the option to verify if Java has been installed correctly. Run that and check

[Guest TheLibrarian]

Are you using an ISA gateway?

 

This was the cause of Java applets failing on sites (eChalk in the first case).

 

The fault was not eChalk; it is to do with XP ignoring the HTTPOnly attribute where 7 does not ignore it.

[Duke5A]

Are you using a proxy of any kind? I've seen proxies mess with Java applets and typically adding the offending sites to the proxy exemption list fixes it. Watch out though, Java will grab proxy settings from whatever the default browser is set to. So if you set you exemptions via GPO for IE, and a particular user has Firefox installed and set as default, Java will pull its proxy settings from Firefox.

[Phil_the_Power]

I've done a bit of testing and it does look like it's to do with our proxy server. Fortunatley the new Java 7 update 4 kind of works. I get an authentication window but can cancel it and Java still works.

 

I'm going to try the script that TheLibrarian has suggested and see if that does anything.

[LukeC]

Did the script work?