关于按钮下拉列表的问题

应该是JToolBar,可以在上面放许多JButton

 Container contentPane=frame.getContentPane();
 toolBar=new JToolBar();
 button=new JButton[2];
 button[0] =new JButton(new FileAction("",icon_openFile,"open file"));
 button[1]=new JButton(new FileAction("",icon_saveFile,"save file"));
 button[0]=SetActionCommand("openFile");
 button[1]=SetActionCommand("saveFile");
 for(int i=0; i<button.length;i++){
 toolBar.add(button[i]);
 }
 contentPane.add(toolBar,BorderLayout.NORTH);
 return contentPane;
 }