JTabbedPaneのタブ描画をフラットデザイン風に変更する

UIManager.put("TabbedPane.tabInsets", new Insets(5, 10, 5, 10));
UIManager.put("TabbedPane.tabAreaInsets", new Insets(0, 0, 0, 0));
UIManager.put("TabbedPane.selectedLabelShift", 0);
UIManager.put("TabbedPane.labelShift", 0);

// UIManager.put("TabbedPane.foreground", Color.WHITE);
// UIManager.put("TabbedPane.selectedForeground", Color.WHITE);
// UIManager.put("TabbedPane.unselectedBackground", UNSELECTED_BG);
UIManager.put("TabbedPane.tabAreaBackground", UNSELECTED_BG);

JTabbedPane tabs = new JTabbedPane() {
  @Override public void updateUI() {
    super.updateUI();
    setUI(new BasicTabbedPaneUI() {
      @Override protected void paintFocusIndicator(
          Graphics g, int tabPlacement, Rectangle[] rects, int tabIndex,
          Rectangle iconRect, Rectangle textRect, boolean isSelected) {
        // Do not paint anything
      }

      @Override protected void paintTabBorder(
          Graphics g, int tabPlacement, int tabIndex,
          int x, int y, int w, int h, boolean isSelected) {
        // Do not paint anything
      }

      @Override  protected void paintTabBackground(
          Graphics g, int tabPlacement, int tabIndex,
          int x, int y, int w, int h, boolean isSelected) {
        g.setColor(isSelected ? SELECTED_BG : UNSELECTED_BG);
        g.fillRect(x, y, w, h);
      }
    });
    setOpaque(true);
    setForeground(Color.WHITE);
    setTabPlacement(SwingConstants.LEFT);
    setTabLayoutPolicy(JTabbedPane.SCROLL_TAB_LAYOUT);
  }
};