When the resource is available both on cached jars and from the
codebase, then applet plugin is throwing the Class cast exception
on its enumeration:
 
Code:
 
      ClassLoader cl = AppletClassLoadingBug.class.getClassLoader();
      System.out.println ("cl :" + cl);
      Enumeration e = cl.getResources("META-INF/MANIFEST.MF");
      while (e.hasMoreElements()) {
        Object oo = e.nextElement();  file://Here it fails.
 .... blah ..blah...
      }
 
Exception :
 java.lang.ClassCastException: java.net.URL
   at sun.plugin.security.PluginClassLoader$2.nextElement
             (Unknown Source)
 at sun.misc.CompoundEnumeration.nextElement(Unknown Source)
 at com.foo.test.AppletClassLoadingBug.
         start(AppletClassLoadingBug.java:21)
 at sun.applet.AppletPanel.run(Unknown Source)
 at java.lang.Thread.run(Unknown Source)
 

  To reproduce, use the html and jar files attached.
See that the codebase also can serve the resource. Eg:
http://host:port/codebase/META-INF/MANIFEST.MF
Should return a valid data.
(Review ID: 143808) 
======================================================================

N/A

Too late for Hopper.   Committ to Mantis.

 xxxxx@xxxxx  2002-05-28

Description of this bus says to use html and jar files attached to the bug.  There are no attachments.  Please provide html and jar file to use to reproduce the problem.

 xxxxx@xxxxx  2002-08-22

Could not reproduce this problem in 1.4.1-rc.  While the problem is reproducible in 1.3.1_02 and 1.3.1_04.  Please contact the submitter and ask them to try their test case with JRE 1.4.1.  I am planning on closing this as "not reproducible".  Please update the bug with submitter's comments.
 xxxxx@xxxxx  2002-09-12

Since it is not reproducible in hopper, uncommitting it for mantis
 xxxxx@xxxxx  2002-10-28

Same sort of stack trace was produced, because the 
above code was run to find a MANIFEST.MF file in an 
extension we are using.

The problem arose in 1.3.1_08 (win 2000) and was 
due to the file:
C:\Program Files\JavaSoft\JRE\1.3.1_08
\lib\applet\WMPNS.jar (Windows Media Player 9 ocx 
control for Netscape) 
Removing that file solved the problem, so try looking 
for it and removing it. 

Placing the jar file from the applet directory to the ext 
directory also fixes the problem for Internet 
Explorer/Mozilla.

FYI, Mozilla also has the same stacktrace when the 
WMPNS.jar is in the applet directory