JTabbedPaneのTabAreaをスクロール

private static void scrollTabAt(JTabbedPane tp, int index) {
  Component cmp = null;
  for (Component c: tp.getComponents()) {
    if ("TabbedPane.scrollableViewport".equals(c.getName())) {
      cmp = c;
      break;
    }
  }
  if (cmp instanceof JViewport) {
    JViewport viewport = (JViewport) cmp;
    for (int i = 0; i < tp.getTabCount(); i++) {
      tp.setForegroundAt(i, i == index ? Color.RED : Color.BLACK);
    }
    Dimension d = tp.getSize();
    Rectangle r = tp.getBoundsAt(index);
    int gw = (d.width - r.width) / 2;
    r.grow(gw, 0);
    viewport.scrollRectToVisible(r);
  }
}