Question

I know you can find the first and last elements in a treeset. What if I wanted to know what the second or third element was without iterating? Or, more preferable, given an element, figure out it’s rank in the treeset.

Thanks

EDIT: I think you can do it using tailset, ie. compare the size of the original set with the size of the tailset. How efficient is tailset?

Answer 1

According to the source of the Sun JDK6 implementation, tailSet(E).size() iterates over the tail set and counts the elements, so this call is O(tail set size).