LinkedHashMap.keys returns the keys of the map in insertion order, but if that collection is manipulated in any way, it reverts to an unordered Set.
This is somewhat surprising, particularly as keys is Iterable.
Welcome to Scala version 184.108.40.206 (OpenJDK 64-Bit Server VM, Java 1.7.0-internal). Type in expressions to have them evaluated. Type :help for more information. scala> val m = scala.collection.mutable.LinkedHashMap("one" -> 1, "two" -> 2, "three" -> 3, "four" -> 4, "five" -> 5) m: scala.collection.mutable.LinkedHashMap[java.lang.String,Int] = Map(one -> 1, two -> 2, three -> 3, four -> 4, five -> 5) scala> m.keys res0: Iterable[java.lang.String] = Set(one, two, three, four, five) scala> m.keys.drop(0) res1: Iterable[java.lang.String] = Set(four, three, two, five, one)