Running applets with the Java Plug-in both in NS Navigator and MS IE leaves the temporary files of the JAR cache in the Windows TEMP directory.
The files remain there after exiting the browsers. This can lead to the drive holding the TEMP directory to fill up, and cause various problems with other Windows programs as well.

When the drive becomes full, the JAR cache stops working and applets will not start. A ClassNotFoundException appears in the Java Plug-in Console due to an IOException in the sun.applet.AppletClassLoader class.

java full version "JDK-1.2-V"
(Review ID: 54124) 
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On Windows NT, the 1.2 Java Plug-in dumps a copy of every jar 
file it downloads into the %TEMP% directory. These files are 
NEVER removed. These files have 
names in the format: jar_cache#####.tmp where ##### is some 
generated number. These files don't get reused if Netscape is 
shutdown and restarted. Instead, a new set of files with a new 
set of names gets downloaded, adding to those already in the 
%TEMP% directory. This occurs even if you have the "Cache 
JARs in memory" disabled in the Java Plug-in Control 
Panel. These files are also distinct from those separately 
cached by the browser. Now the browser periodically cleans up 
it's cache but these jar_cache####.tmp files are never cleaned
up, they just suck up more and more disk space.
(Review ID: 63194)
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The temporary jar-files created in the TEMP directory when you download classes are not removed when you exit from the browser.
We have tried to disable JIT , which fix the iexplore.exe process cleanup (bug 4225985), but the temporary files are still in the temporary directory.

Our application loads about 11 MB of temporary files into TEMP each time the applet is started.
(Review ID: 83301)
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Plug-in always download the jar file even when there is no changes in the jar file. Also, the downloaded jar files are stored in system temp directory and new ones are added to the temp directory every time you run the the same app.

User's hard dirve fills up with the downloaded jar files within few days.

Does any body have solution to theis problem? Could way my jar file is created cause this?
(Review ID: 88345)
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Using HTTP session browser (observed with  NS 4.6), when large 
applets loaded from web, jar_cacheXXXXX.tmp files remain in 
C:\TEMP applet, plug-in and browser exit. This consumes C: disk 
space and will cause operational problems (performance, data loss,
program hang, etc) due to lack of C:\ space.

java -version = 1.2.2 Final
(Review ID: 95391)
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=20
When loading JAR files with the Java Plug-In these files will
not only be cached by the browser. They also appear in the
Windows TEMP directory with a name like jar_cache21122.tmp.
They are stored in the TEMP directory every time the applet
is run, not only once like in the browser cache.

These files are not removed when the Plug-In is terminated.
They gradually take up a lot of directory entries. At least
they now seem to be truncated to 0 bytes.

Jerome Dochez from Sun told me at the JAVADAYS'99 that this
is not a bug of the Plug-In but a problem in the java.net.*
classes.

This bug also exists with the older releases of Java.
There the files kept their size so they actually filled up
your hard disc.
(Review ID: 95887)
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We have an applet with a jar file of size 867 KB.   Each time the applet is opened in Netscape or Internet Explorer browser a file named jar_cacheXXXXX.tmp (there is a unique number in place of XXXXX)is created in D:\TEMP directory and never cleaned up.  If I open our applet 10 times, I will see 10 jar_cacheXXXXX.tmp files.  There is also a jar file in web brower's cache directory.  Plugin should clean up the jar_cacheXXXXX.tmp file in TEMP directory whenever browser is closed.  Or it should use the file in browser's cache and should not copy it to TEMP directory.  It runs out of disk space eventually and cannot start the applet.
(Review ID: 96912)
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we got a prob, when we were trying to open broswer its downloading the jar files to temp directory, 
if i close it  and  again cameback  to same application in the browswer its again creating same jars files 
with different names in temp directory. I am loosing my H.Disk space. Anybody can help me.

Thanks,
Niru.
(Review ID: 96980)
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java version "1.2.2"
Classic VM (build JDK-1.2.2-W, native threads, symcjit)


When downloading a Java applet (built with JDK 1.2.2) JAR file using the Java
Plug-in 1.2.2 utility, it creates a temporary copy of the JAR file on the hard
disk and does not remove it when the applet is destroyed.  Everytime the applet
is loaded, a new copy of the JAR file is created and eventually fills the hard
disk.  The temporary JAR files are named jar_cache?.tmp and placed in the
directory set for temporary internet files.  Removing the temporary internet
files from the browser option does not remove these files.  Also, turning off
the Java Plug-in Control Panel setting for "Cache JAR's in memory" does not
resolve the issue either.
(Review ID: 98555)
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java -version
java version "1.2.2"
Classic VM (build JDK-1.2.2-001, native threads, symcjit)

The user downloads and installs 1.2.2 JRE to run the applets in the system.
When the user goes to view the applets, plug-in downloads jar files to be used
to the users system.  These files are placed both in the Temporary Internet
Files folder (where expected) and in the regular NT temp directory.  The issue
here is that whenever the user clears their browser cache and views the applet
again, a new jar is placed in both locations.  In the Temporary Internet Files
folder, this is the only instance of the jar, so that is fine.  In the NT temp
directory, these jar files continuosly build up (they are all suffixed with
random numbers).  The applet runs fine, the issue is that these files are
building up in the users temp directory without them  customer .
(Review ID: 100837)
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Periodically delete the jar_cache*.tmp files from the TEMP directory.
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Manually delete the files from the temp directory every so often
(Review ID: 63194)
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None.
(Review ID: 88345)
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Manually or programatically periodically clean out jar_cache files in 
C:\TEMP (NT) or C:\Windows\Temp in 95/98.
(Review ID: 95391)
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=20
Go to the TEMP directory and clear out the files manually.
Bug make sure that the Plug-In is not running!
(Review ID: 95887)
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Clean up the TEMP directory often.
(Review ID: 96912)
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Delete the temporary files manually until the problem is resolved.  Not
reasonable for final deployment of the applet in JAR form...
(Review ID: 98555)
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This is a JDK bug, the bugID is 4166799. It has been fixed in Kestrel.

  xxxxx@xxxxx   2000-02-04

This also happens in Win 95, but it seems that the files become 0 bytes...

Plugin is not working with this bug, since we don't want to educate thousands
end users.

To Javasoft:  Workarounds that suggest the
end-user must fix this problem are completely
missing the point.  Deploying an applet that
requires a Java plug-in MUST NOT involve any
end-user maintenance.  The sites where our
application will be deployed will have thousands
and thousands of users, and this would be a
help-desk nightmare.  We need a fix at least in
the 1.3 FCS release, if not as a patch to 1.2.2!

Java sucks!

Great idea, why didnt I think of cleaning the temps manually manually... Get this fixed, or I'll never use java 
again...