@Override
  public void focusGained(FocusEvent e) {
    if (e.getSource() instanceof JList) {
      JList list = (JList) e.getSource();
      if (list.getSelectedIndex() < 0 && list.getModel().getSize() > 0) {
        list.setSelectedIndex(0);
      }
    }
  }
When component gained focus is list without selection, first element is selected.
olv-vfs/src/main/java/pl/otros/vfs/browser/list/SelectFirstElementFocusAdapter.java