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.
A real-time system is one that is subject to a time constraint. Meaning, something has to be done at a precise time, or within a deadline from when some real-world even occurs. Java SE is not predictable enough to build hard real-time systems with; you cannot guarantee your code can respond in time to an event to meet its deadlines. Java RTS is a separate VM implementation that works with real-time OS's such as Solaris 10, and Linux with real-time patches, to guarantee this.