LinkedHashMap

LinkedHashMap is a HashMap that remembers the order in which entries were added. It provides the same average O(1) get and put as HashMap, while iteration walks the entries in a predictable order rather than the scrambled bucket order a plain HashMap produces. It also has a second mode, access order, which fits building a small LRU cache. This lesson covers both modes, the doubly-linked list that makes them work, how to bound the size by overriding removeEldestEntry, and when picking LinkedHashMap over HashMap or TreeMap is appropriate.