import java.util.ArrayList; import java.util.Set; import java.util.TreeSet; public class SetUtil { /** Determine the strings that are unique to words1 and words2 @param words1 an array of strings @param words2 an array of strings @param a list of two sets: the words that are in words1 but not word2, and the words that are in words2 but not word1. The sets should be sorted. */ public static List<Set<String>> uniqueInEach(String[] words1, String[] words2) { ... } }