public void actionPerformed(ActionEvent e) {
   if (e.getSource() == top) {
     tabbedpane.setTabPlacement(JTabbedPane.TOP);
   } else if (e.getSource() == left) {
     tabbedpane.setTabPlacement(JTabbedPane.LEFT);
   } else if (e.getSource() == bottom) {
     tabbedpane.setTabPlacement(JTabbedPane.BOTTOM);
   } else if (e.getSource() == right) {
     tabbedpane.setTabPlacement(JTabbedPane.RIGHT);
   }
 }