Quoth the SCJP study guide:
Arrays are efficient, but most of the time you'll want to use one of the Collection types from java.util (including HashMap, ArrayList, TreeSet). Collection classes [… a]re really managed arrays, since they use arrays behind the scenes. […]
ORLY. Show me how a TreeSet uses arrays behind the scenes. Or a LinkedList, which—though they didn’t mention it explicitly—is also “one of the Collection types from java.util”.)
If this goes on much further, I’ll have to create a separate entry just for their weirdness rather than posting as I go along.