static class LogView extends JScrollPane {
  JTextArea textArea;

  *() {
    textArea = new JTextArea;
    textArea.setEditable(false);
    setViewportView(textArea);
  }

  // thread safe
  public void logText(final String text) {
    awt {
      textArea.append(text);

      // todo: scroll?
    }
  }
  
  // thread safe
  void print(String text) {
    logText(text);
  }

  // log some pure text and add a line feed
  // thread safe
  public void println(String line) {
    logText(line + "\n");
  }
  
  // thread safe
  public void clear() {
    awt { textArea.setText(""); }
  }
}

Began life as a copy of #1000815