What purpose does the newSetFromMap() method offer if I can just create something like a HashSet instead of a HashMap?
Created May 14, 2012
John Zukowski The Set returned by newSetFromMap() functions with the same ordering and concurrency characteristics of the map it is based off of. Some Map implementations also have a related Set implement, so using this method doesn't really help. That's the case with HashMap/HashSet and TreeMap/TreeSet. However, not all maps have this common partner. For instance, while there is a WeakHashMap, there is no WeakHashSet. Other user-generated collections might have similar situations. While you can get something like the key set from a Map, it won't be as closely tied to the underlying collection.