You're having trouble keeping track of all these lists, sets, and iterators.
There's a pattern to it. See Figure 7-3 and Table 7-2.
Figure 7-3, in the fashion of the package-level class diagrams in the O'Reilly classic Java in a Nutshell, shows the collection-based classes from package java.util.
Figure 7-3. The Collections Framework
The Javadoc documentation on Collections, Arrays, List, Set, and the classes that implement them provides more details than there's room for here. Table 7-2 may further help you to absorb the regularity of the Collections Framework.