// x = names and components interleaving.

// or just components.

// or just names.

// also, first element can be index of tab to open at start

// also, SUPER short demo syntax: jtabs(3)

// also, you can pass a Collection containing the elements

static JTabbedPane fillJTabs(final JTabbedPane tabs, fO... _x) {

  if (tabs == null) null;

  clearTabs(tabs);

  O[] x = flattenArray2(_x);

  ifdef fillJTabs_debug

  print("fillJTabs length=" + l(_x) + " => " + l(x));

  endifdef

  int idx = 0;

  if (get(x, 0) instanceof Int) {

    idx = asInt(get(x, 0));

    x = dropFirst(x);

    if (empty(x)) {

      x = arrayrep(null, idx);

      idx = 0;

    }

  }

  int n = 0;

  for (int i = 0; i < l(x); i++) {

    ++n;

    // is it a component?

    O o = x[i];

    if (isComponentOrSwingable(o))

      addTab(tabs, "Tab " + n, wrap(o));

    else {

      // assume it's a tab name, optionally followed by a component

      S toolTip = "";

      // WithToolTip<S> is ok (WithToolTip<Component> not yet supported)

      if (o cast WithToolTip) {

        toolTip = o.toolTip();

        o = o!;

      }

      S name = str(or(o, "Tab " + n));

      ifdef fillJTabs_debug

      print("tab " + i + ": " + name);

      endifdef

      Component c;

      if (isComponentOrSwingable(get(x, i+1)))

        c = wrap(get(x, ++i));

      else

        c = new JPanel;

      addTabWithToolTip(tabs, name, toolTip, wrap(c));

    }

  }

  if (idx != 0)

    tabs.setSelectedIndex(min(tabs.getTabCount()-1, idx));

  ret tabs;

}