In this level, you continued to get acquainted with collections: you figured out what HashMap and TreeMap are, and also learned more about the methods of the Collections helper class.

In general, we suggest that you breathe in and breathe out, and then close out these topics completely (for now) — carefully read a few additional lessons. It will not be boring!

HashMap: what kind of map is this?

TreeMap in Java

Collections in Java

Collections class in Java