sclass AutoCompleter {
  void addValue(S s) {}
  S completeInput(S s) { ret ""; }
}

sclass LocalAutoCompleter {
  new TreeSet<S> entries;
  
  void addValue(S s) { entries.add(s); }
  
  S completeInput(S s) {
    S completion = firstStartingWith(entries, s);
    ret completion != null ? dropPrefix(s, completion) : "";
  }
}

static JTextField autoCompleteTextField(JTextField tf) {
  final new LocalAutoCompleter completer;
  onEnter(tf, r {
    completer.addValue(tf.getText());
  });
  /*onComponentHide(tf, r {
    completer.addValue();
  );*/
}