public class Words
{
   /**
      Gets the middle character or character pair from this word
      when possible.
      @param word a word
      @return the middle character (if the word length is odd) or
      middle two characters (if it is even), or the empty string if
      the word is empty, or null if it is null.
   */
   public String getMiddle(String word)
   {
      if(word == null)
      {
         return null;
      }
      else if(word.length() == 0)
      {
         return " ";
      }
      else if(word.length() % 2 == 0)
      {
         return word.substring((int)(word.length()/2-1),(int)(word.length()/2+1));
      }
      if(word == null)
      {
         return "null";
      }
      else
      {
         return String.format("%c",word.charAt((int)(word.length()/2)));
      }
   }
}