public void add(Word wd)
   {  if (this.numUsed >= this.words.length)
      {  Word[] newList = new Word[this.words.length * 2];
         for (int i = 0; i < this.numUsed; i++)
         {  newList[i] = this.words[i];
         }
         this.words = newList;
      }
      this.words[this.numUsed] = wd;
      this.numUsed++;
   }