Today I started to do something that I am sure it was needed long time ago already. I took the latest GNU Classpath distribution and started to rip some selected interesting package, java.util, apart. One time I will check properly if it is worse or maybe same or maybe better the one we have got from Sun.
GNU Classpath has been written over long time by numerous developers. In addition, it usually runs with the different java virtual machine than the Sun's code. In that way, no honest comparison is possible between any units that are smaller than all jre + all rtl together.
So, that I have done so far I moved the chosen set of GNU Classpath java.util classes into some transient package where they do not conflict with java.util from Sun. Some code editing was needed to build everything but in general it was trivial to build it that way. Now I have the two java.util's on the same virtual machine! It is time to try some performance comparison. We will just write some simple tests for that. Stay tuned.