JPanel panel;
        GridBagConstraints c =  new  GridBagConstraints();
        container.setLayout( new  GridBagLayout());

        c.weighty =  1 . 0 ;
        c.weightx =  1 . 0 ;
        c.gridy =  0 ;
        c.fill = GridBagConstraints.BOTH;
        Color color = Color.RED;
         for ( int  i =  0 ; i <  2 ; i++) {
                c.gridx = i;
                panel =  new  JPanel();
                panel.setBackground(color);
                container.add( panel, c );
                color = (color == Color.RED) ? Color.WHITE : Color.RED;
        }