public int addCreature(Creature newCreature) {
        // if the passed in creature creature doesn't exist, don't add it
        if ( newCreature == null )
        {
            return -1;
        }
        
        // if we already contain the creature, don't attempt to add it
        if (findCreature(newCreature.getName()) != null) {
            return -1;
        }
        
        // make some room
        increaseArray();

        // assume increaseArray() increases by one
        // and the new element is empty...
        
        // add the new creature to the list
        creatureList[creatureList.length-1] = newCreature;
        return creatureList.length-1;
	}