This week's book giveaway is in the Mac OS forum. We're giving away four copies of a choice of "Take Control of Upgrading to Yosemite" or "Take Control of Automating Your Mac" and have Joe Kissell on-line! See this thread for details.
They are not really compatible. Jikes is a compiler, which takes source code and generates bytecode ready to give to a JVM. Hotspot is a JVM (or at least a speed-up module for one) which takes bytecode and runs it.