JRE Proliferation -- any way to get a handle on it?

Question

I'm relatively new to JAVA, and come from a (ugh) mainframe background, so, please, no rocks or stones....
My old machine at work crashed and I'm breaking in a new laptop, WinXp, installing all the tools needed to get the job done.
Why does every JAVA tool insist on installing it's own JRE??? In a time period of less than a month, I now have 21 separate copies of JAVA.EXE on my system. Heck, I've just installed one tool suite from a vendor and it installed 4 separate JRE directories!
Now, I'll admit to installing 2 of them myself to suport a small JAVA project... and I sort of understand software builders/vendors want to ensure their product runs on a fully compatible JRE/JVM... but most times the install process doesn't even bother to check to see if there is a compatible JRE already installed.
This seems to already be out of control.... and new and improved versions of JAVA will always be coming out.
Is there a way to get a handle on all this proliferation? A (java) program that works like a version manager? Someone with a big stick offering guidance to developers/vendors?
thanks for your insight (and letting me vent)

Answer 1

In my experience, many of the applications that require Java that I use do not install the JRE unless I specify that I have no version of Java installed. It seems that the applications you have installed are different in this regard. So I've never had the problem you describe but I can offer an idea. I don't know if it will work for you.
In any case, generally speaking, most Java programs that I have worked with like Tomcat, Oxygen and so forth will make use of an environment variable called JAVA_HOME to locate the base directory of the current working java installation, and from there use the JRE. So my thought would be to pick the most recent stable version of Java you have installed installed on the system, and set the JAVA_HOME variable to point to this directory. Then < possibly > you could eliminate the other versions of Java installed on the system. But it very much depends on how these applications are finding Java. It could be the applications are using a hard coded path to the directory, even though from a developer's perspective I think that is nonsense. But I just don't know for sure. So you would want to be cautious about deleting the other versions, maybe disable them by renaming the directories to see if any applications are depending upon it. Then if no errors occur delete the version.
Just my two cents. Perhaps others will have other ideas.