public int compareTo(Object o) {
   Speaker otherSpeaker = (Speaker) o;
   if (otherSpeaker.name().equals(name)) {
     this.occurrance += otherSpeaker.occurrance();
     otherSpeaker.occurrance = this.occurrance;
     return 0;
   }
   return name.compareTo(otherSpeaker.name());
 }