Which JVM to use?

[Philip Shanks]

I have a class that I put together, loosly based on some Microsoft sample code:

import com.ms.util.*;
import java.util.*;
class SafeVMTest
{
   public static void main(String[] args)
   {
      Properties props = SystemVersionManager.getVMVersion();
      Enumeration enum = props.keys();
      while (enum.hasMoreElements()) {
          String key = (String) enum.nextElement();
          System.out.println(key + ": " + props.getProperty(key));
      }
   }
}

And then I made sure that the com.ms.util.SystemVersionManager class could be found in com\ms\util\ in the same directory as my Java source file (I extracted it from a zip archive that is part of the MS Virtual Machine installation for Win2000).
It compiled just fine, and then, just to make sure I knew what JVM I am calling when I run "java" from the command line, I did this:

C:\Java Projects\Demos>java -version
java version "1.4.0"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.4.0)
BEA Weblogic JRockit(R) Virtual Machine (build 7.0-1.4.0-win32-GARAK-20020830-1714, 
Native Threads, Generational Concurrent Garbage Collector)

And then I ran my code. Now I was expecting errors galore, as it would be highly unusual for the BEA JVM to mimic very closely the MS VM. But what I actually got was wholly unexpected. The code ran in the native MS VM!
Output:

C:\Java Projects\Demos>java SafeVMTest
MajorVersion: 4
BuildIncrement: 1158
BuildNumber: 0
Description: Microsoft (R) VM for Java, 3.0 Release
MinorVersion: 79

Some other relevant info:

C:\Java Projects\Demos>echo %JAVA_HOME%
c:\JRockit\7.0\1.4.0
C:\Java Projects\Demos>echo %PATH%
c:\JRockit\7.0\1.4.0\bin\;C:\WINNT\system32;C:\WINNT;C:\WINNT\System32\Wbem;C:\Perl\bin

No CLASSPATH is set.

So, what the heck just happened?
PCS
[ November 20, 2002: Message edited by: Philip Shanks ]

[Cindy Glass]

Are you sure that no classpath is set?
Open a DOS window and at the prompt type
>set
then look for the classpath parameter.
(or you can use the "echo %classpath%" command)
If the code that you executed only uses classes up to the level that MS has loaded it would work correctly.

[Philip Shanks]

I just confirmed... no %CLASSPATH% environment variable. Somehow, by accessing the com.ms.util.SystemVersionManager, the code winds up executing in the MS VM.

[Anonymous]

I just happened to open the mentionned class in Decafe (Java decompiler). The values are actually hard-coded into the class
Hence, I'm pretty convinced you've still be running the same VM as before