public class RandomizedQueue implements Iterable {
   public RandomizedQueue()                 // construct an empty randomized queue
   public boolean isEmpty()                 // is the randomized queue empty?
   public int size()                        // return the number of items on the randomized queue
   public void enqueue(Item item)           // add the item
   public Item dequeue()                    // remove and return a random item
   public Item sample()                     // return a random item (but do not remove it)
   public Iterator iterator()         // return an independent iterator over items in random order
   public static void main(String[] args)   // unit testing (optional)
}