Padma, you're mistaken.. see:
1- HashSet: iteration order is NOT predictable, since *I guess* it depends on the hashCode() int value of the objects, or it uses an algorithm that you need not know for the exam, all you need to know is that it's unpredictable. So HashSet collection are actually NOT ordered.
2- LinkedHashSet: ARE ordered by the order elements were inserted, you can also instruct it to order elements by which one was last accessed - this is important - so Iteration order is according - by default - to the insertion order.
3- TreeSet: is not only ordered but it is Sorted, Sorted means it iterates the elements ascendingly - if this is how you spell it
-according to their "Natural Order" and NOT by the order they were inserted. Natural Order depends on the type of the Objects inserted, for instance String
elements will be ordered alphabetically, Integer Objects will be ordered according to their mathimatical values - remember, you can't insert int into a collection, since it's a premitive, not an Object -. More over you can instruct the TreeSet to sort elements in your own specifications.
So for instance if HashSet will iterate elements like "four", "two", "five", "one" then if this is inserted - with this order - to a LinkedHashSet, it will iterate them the same way... BUT a TreeSet will "sort" them as - ok a b c d e f hehehe - "five", "four", "one", "two"
Got the picture?