Also, how would this be different if Node was used as an implementation instead of Link ?

"Since sets and bags are unordered collections, how is it that we are able to determine whether they contain a particular item?" the Galaxers ask. Since we know the size of the collection, we can traverse the structure to see if the given item is present. In fact, the any data structure. Let me write it for you using a linked structure that makes use of an inner class Link public boolean contains (T item)