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.
Runtime is an abstract class. There is no direct way to instantiate it. It has a static method to get an instance of some unknown subclass. This method is called getRuntime(). Therefore, Runtime.getRuntime() returns an instance of a subclass of Runtime.
totalMemory() is an instance method that you call on that instance. Your single line is similar to this: