// http://codingbat.com/prob/p190862

public Map<String, Boolean> wordMultiple(String[] strings) {
  Map<String, Boolean> map = new HashMap<String, Boolean>();
  for (String word : strings) {
    if (map.containsKey(word)) {
      map.put(word, true);
    }
    else {
      map.put(word, false);
    }
  }
  return map;
}

Create wordMultiple.java