code: public boolean contains( Object o )
    {
      boolean result = false;
      if( o == null ) {
        result = false;
      }
      else if( o instanceof String ) {
        result = super.contains(convertAddress((String)o));
      }
      else if( o instanceof InternetAddress ) {
        result = super.contains(o);;
      }
      return result;
    }
docs: Returns true if o is an instance of InternetAddress and is in the set.  Returns true if o is an instance of String
  and the set contains InternetAddress(o).  Returns false in all other cases, including when o is null.