Auto complete (known as intelsense on visual studio) is a great way of speeding up coding. Especially if you can not remember the exact name of a command. Auto complete lets you remember attribute or method names of any class or object that is in netbeans class path.
if you type "System.out" and then press full stop you should see a pop up appear like the one below -
You can then select one of the options. This happens ONLY when you have typed the name of a object or class in. To be more specific if you enter a class name and then press full stop then you will only get static methods.