FIX: NoClassDefFoundError When a Valid Class Definition Exists

• Microsoft Internet Explorer version 4.0 for Windows NT 4.0
• Microsoft Internet Explorer version 4.0 for Windows 95
• Microsoft SDK for Java, version 2.0

SYMPTOMS

A Java applet or program that attempts to load certain valid Java classes may fail with a NoClassDefFoundError exception.

If the applet is running inside Internet Explorer, there may be no visible symptoms, except that the applet does not run properly. If Java Logging is enabled in Internet Explorer. However, the file Javalog.txt file, created in the Java subdirectory of the Windows directory, contains a log of the exception and a call stack. Here is a typical example of the exception:

java.lang.NoClassDefFoundError: COM/objectspace/jgl/HashMap

CAUSE

The Microsoft virtual machine verifies that the .class file that defines each Java class is valid before loading it. Version 4.79.2252 erroneously decides that certain .class files are not valid, and therefore, fails to load them. When it fails to find a valid definition for a class, the Microsoft virtual machine throws a NoClassDefFoundError exception.

RESOLUTION

Download and install the current Microsoft virtual machine from the following Web site:

http://www.microsoft.com/java/download.htm

STATUS

Microsoft has confirmed this to be a bug in the Microsoft products listed at the beginning of this article. This bug was corrected in Microsoft virtual machine, version 4.79.2334 and later.

MORE INFORMATION

One class that the Microsoft virtual machine fails to validate is the HashMap class from ObjectSpace's JGL class library. It is possible to produce other .class files that the Microsoft virtual machine will fail to validate using a Java compiler, including Microsoft's Visual J++ or SDK 2.0 for Java.

Steps to Reproduce Behavior

import COM.objectspace.jgl.*;
public class HashMapTest
{

   public static void main (String args[])
   {
      HashMap    hm = new HashMap();
   }

} 

REFERENCES

JGL is manufactured by ObjectSpace, Inc., a vendor independent of Microsoft; we make no warranty, implied or otherwise, regarding this product's performance or reliability.

Further information about JGL can be found at the following Web site:

http://www.objectspace.com/jgl/

http://support.microsoft.com/support/visualj/

http://support.microsoft.com/support/java/

Additional query words: NoClassDefFoundError

Keywords          : kb3rdparty kbJavaVM kbSDKJava 
Version           : WINDOWS:2.0,4.0
Platform          : WINDOWS 
Issue type        : kbbug 

Last Reviewed: July 26, 1999