How Many JVMs Does One Need?

Hey, Ted:

How can I find out how many Java Virtual Machines are on my PC? I'm guessing that I have one from Client Access (to run Operations Navigator), possibly another from WebSphere Developer Studio client, another from Surveyor/400 (which are all Java on the client), and one from Microsoft that comes with Windows XP.

This is somewhat of a curiosity question, but if I have OpsNav, WDSc and Surveyor all running at the same time, I suspect I may be using three JVMs simultaneously and increasing my paging rate. Any thoughts?

--Sam

I referred your question to Fred Kulack of IBM, and this is what he had to say:

Applications can't assume that the correct level of Java (with the right fixes, from the right vendor) will be present on the target operating system. Many operating systems do not provide a way for one application to indicate that it is dependent on another application (e.g., a certain version of the JVM). I think some of the Unix variants (including Linux) support this with their package managers. As far as I know, Windows does not.

For this reason, application developers usually ship the Java runtime environment (JRE) that the application depends on and has been tested with.

The problem gets compounded when one Java product includes another Java product. For example, many Java applications include the Java version of InstallShield.

This is perceived as an irritant with Java today. Any "third party" library or "middleware" application that you use could possibly fall into this problem area, too. Having multiple versions of the JVM on one machine is a common issue.

Maybe this is not a very high-tech solution, but I search my PC's hard disk for one of the files included in the JRE. I found 12 files named java.exe on my system, only two of which I had installed manually, for a total of 500 MB of disk space.

--Ted

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