public String put(String name, String key, String value)
   {
      modified = true;
      for (Item it : items)
      {
         if (name.equals(it.getName()) && key.equals(it.getKey()))
         {
            String oldValue = it.getValue();
            it.setValue(value);
            return oldValue;
         }
      }
      items.add(new Item(name, key, value));
      return null;
   }