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.

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On the 32-bit Windows platform, JVM programs can only ever use up to about 1.5–1.6 GiB of memory in RAM per Java VM process. Allocating a heap size greater than this amount does not work. What's going on?

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I've been playing with customising jEdit a little bit, and decided to have a go at writing some simple date insertion macros. These perform the same work as some old elisp functions I wrote years ago in Emacs, to insert date/time stamps in various formats. In my .emacs file, I bind these functions to short-cut keys, and then use them for updating Changelogs in code and in offline journal entries.

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