Any implementation of Ordered Set in Java?

Question

If anybody is familiar with Objective-C there is a collection called NSOrderedSet that acts as Set and its items can be accessed as an Array

Answer 1

If we are talking about inexpensive implementation of the skip-list, I wonder in term of big O, what the cost of this operation is:

YourType[] array = someSet.toArray(new YourType[yourSet.size()]);

I mean it is always get stuck into a whole array creation, so it is O(n):

java.util.Arrays#copyOf