I think now that we're dependent on JDK 1.5+, there is a JMX-related sizeof method we can use to find out the exact size of a given object in memory. We might want to switch to that.
For 1.3 we're still on JDK 1.4 I'm afraid. But we could hide the sizeOf behind a strategy and deliver a single jar (as it needs a manifest describing the instrumented class) with the instrumentation based implementation. More: http://www.jroller.org/page/maxim?entry=again_about_determining_size_of Eelco
