WordPairList Solution - AP 2018 FRQ - https://clsc.be/26

PartA.java

public WordPairList(String[] words) {
  allPairs = new ArrayList<>();
  for (int i=0; i<words.length; i++)
    for (x=i+1; x<words.length; x++) 
      allPairs.add(new WordPair(words[i], words[x]);
}

PartB.java

public int numMatches() {
 int cnt = 0;
 for (WordPair wp: allPairs)
    if (wp.getFirst().equals(wp.getSecond())
        cnt++; 
  return cnt; 
}