JComboBox+JButton生成類似IE前進後退按鈕,請高手幫助指正（还有一贴，解决分全给）

http://community.csdn.net/Expert/topic/3191/3191872.xml?temp=.2467005分都在这个帖子上！
class ComboBoxRenderer extends JButton implements ListCellRenderer {   JSeparator separator;   final String SEPARATOR = "SEPARATOR";   public ComboBoxRenderer() {     setOpaque(true);     setBorder(new EmptyBorder(1, 1, 1, 1));     separator = new JSeparator(JSeparator.HORIZONTAL);   }   public Component getListCellRendererComponent( JList list,          Object value, int index, boolean isSelected, boolean cellHasFocus) {     String str = (value == null) ? "" : value.toString();     if (SEPARATOR.equals(str)) {       return separator;     }     if(isSelected) {       setBackground(list.getSelectionBackground());       setForeground(list.getSelectionForeground());     } else {       setBackground(list.getBackground());       setForeground(list.getForeground());     }     setFont(list.getFont());     setText(str);     return this;   } }    Object[] obj={"1","2","3"};    jComboBox1=new JComboBox(makeVectorData(str));    jComboBox1.setRenderer(new ComboBoxRenderer());但生成的和IE的前進 後退 按鈕 差的 太遠，那 位高手能 幫幫忙 ！