private void showContent(@NotNull Content content) {
    if (myPanel.getComponentCount() != 1 ||
        myPanel.getComponent(0) != content.getComponent()) {
      myPanel.removeAll();
      myPanel.add(content.getComponent(), BorderLayout.CENTER);

      myPanel.revalidate();
      myPanel.repaint();
    }
  }
private void showContent(@NotNull Content content)