public String lookup(String data){
  Iterator<String> it=map.getPrefixedBy(data);
  if (!it.hasNext())   return null;
  return it.next();
}

public String lookup ( String data ) { Iterator < String > it = map . getPrefixedBy ( data ) ; if ( ! it . hasNext ( ) ) return null ; return it . next ( ) ; }
return the last string in the set that can be prefixed by this string ( trie ' s are stored in alphabetical order ) . return null if no such string exist in the current set .
