It is useful to have different versions of the JVM installed, for a number of reasons:
- Different optimisation features from different JVM implementations
- Different language features from different JVM versions
- Java classes compiled with “Tiger” won't run in “Mantis”…
It is also useful to be able to quickly switch between installed JREs/JDKs depending on the task at hand.
If I'm hacking in Linux, the JPackage project provides a much nicer solution to this problem, and the Linux distro' I'm using (SUSE 10.0) uses JPackage. It'd be nice if there was an
update-alternatives for Cygwin, but since there isn't I've come up with this hack.