JTextAreaの任意の行まで移動

JButton button = new JButton(new AbstractAction("Goto Line") {
  @Override public void actionPerformed(ActionEvent e) {
    Document doc = textArea.getDocument();
    Element root = doc.getDefaultRootElement();
    int i = Integer.parseInt(textField.getText().trim());
    i = Math.max(1, Math.min(root.getElementCount(), i));
    try {
      Element elem = root.getElement(i - 1);
      Rectangle rect = textArea.modelToView(elem.getStartOffset());
      Rectangle vr = scroll.getViewport().getViewRect();
      rect.setSize(10, vr.height);
      textArea.scrollRectToVisible(rect);
      textArea.setCaretPosition(elem.getStartOffset());
    } catch (BadLocationException ex) {
      Toolkit.getDefaultToolkit().beep();
    }
  }
});
EventQueue.invokeLater(() -> getRootPane().setDefaultButton(button));