collections - singletons

■ Collections provides three methods which accept an Object and return an immutable single-Object List, Set, or Map.

■ Note the default naming for the Set:

singletonList(Obj) returns a List i.e.

List ls = new ArrayList(Collections.singletonList("abc"));

Collections.singletonMap("1", "A"); returns a Map

HashSet hs = new HashSet(Collections.singleton("xyz")); returns a Set