public String toString() {
   String returnMe = "";
   for (int i = 0; i < this.getData().size(); i++) {
     WordIndex WI = (WordIndex) this.getData().get(i);
     returnMe += WI.getWord() + "\n";
   }
   return (returnMe);
 }
 /** Get the key used in comparison. */
 public Object getKey(Object o) {
   WordIndex temp = (WordIndex) o;
   return ((Object) temp.getWord());
 }