Practice-It

Write a method called acronyms that takes a set of word lists as a parameter and that returns a map whose keys are acronyms and whose values are the word lists that produce that acronym. Acronyms are formed from each list as described in problem 1. Recall that the list [laughing, out, loud] produces the acronym "LOL". The list [League, of, Legends] also produces the acronym "LOL". Suppose that a variable called lists stores this set of word lists:

[[attention, deficit], [Star, Trek, Next, Generation],
 [laughing, out, loud], [International, Business, Machines],
 [League, of, Legends], [anno, domini], [art, director],
 [Computer, Science and, Engineering]]

Each element of this set is a list of values of type String. Assume that each list is nonempty and that each string in a list is nonempty.

Your method should construct a map whose keys are acronyms and whose values are sets of the word lists that produce that acronym. For example, the call acronyms(lists) should produce the following map:

{AD=[[attention, deficit], [anno, domini], [art, director]],
 CSE=[[Computer, Science and, Engineering]],
 IBM=[[International, Business, Machines]],
 LOL=[[laughing, out, loud], [League, of, Legends]],
 STNG=[[Star, Trek, Next, Generation]]}

Notice that there are 5 unique acronyms produced by the 8 lists in the set. Each acronym maps to a set of the word lists for that acronym. Your method should not make copies of the word lists; the sets it constructs should store references to those lists. As in the example above, the keys of the map that you construct should be in sorted order. You may assume that a method called acronymFor is available that takes a list of strings as a parameter and that returns the corresponding acronym. Your method is not allowed to change either the set passed as a parameter or the lists within the set. The sets that you construct for the new map will have to be of type HashSet (we will explore why later in the course).