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

Take a look at the Java standard API doc. Right next to LinkedHashMap, there is a LinkedHashSet. But note that the order in those is the insertion order, not the natural order of the elements. And you can only iterate in that order, not do random access (except by counting iteration steps).

There is also an interface SortedSet implemented by TreeSet and ConcurrentSkipListSet. Both allow iteration in the natural order of their elements or a Comparator, but not random access or insertion order.

For a data structure that has both efficient access by index and can efficiently implement the set criterium, you'd need a skip list, but there is no implementation with that functionality in the Java Standard API, though I am certain it's easy to find one on the internet.