JPopupMenuが枠しか表示されない

import java.awt.BorderLayout;

import java.awt.event.MouseAdapter;

import java.awt.event.MouseEvent;



import javax.swing.JFrame;

import javax.swing.JList;

import javax.swing.JMenuItem;

import javax.swing.JPanel;

import javax.swing.JPopupMenu;

import javax.swing.JScrollPane;

import javax.swing.JSeparator;

import javax.swing.JSplitPane;



public class Test extends JPanel {



	public static void main(String[] args) {

		Test test = new Test();

		JFrame frame = new JFrame("Test");

		frame.getContentPane().add(test);

		frame.setBounds(100, 100, 320, 240);

		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

		frame.setVisible(true);

	}



	private JList list;

	private JScrollPane scrollForList;



	private JPanel panel1;

	private JScrollPane scrollForPanel1;



	private JPanel panel2;

	private JScrollPane scrollForPanel2;



	private JPopupMenu popup;



	public Test() {

		super(new BorderLayout());



		list = new JList(new String[] {

			"abcdefg",

			"1234567",

			"あいうえお",

			"ABCDEFG",

			"こんにちは",

			"Digital Research",

			"Sun Microsystems Inc.",

			"IBM",

			"Oracle",

			"BEA"

		});

		list.addMouseListener(new MouseAdapter(){

			public void mouseReleased(MouseEvent ev){

				if(ev.isPopupTrigger())

					popup.show(ev.getComponent(),

						ev.getX(),

						ev.getY());

			}

		});

		scrollForList = new JScrollPane(list);



		panel1 = new JPanel();

		scrollForPanel1 = new JScrollPane(panel1);



		panel2 = new JPanel();

		scrollForPanel2 = new JScrollPane(panel2);



		JSplitPane split2 = new JSplitPane(JSplitPane.HORIZONTAL_SPLIT,

			scrollForList,

			scrollForPanel1);

		JSplitPane split1 = new JSplitPane(JSplitPane.VERTICAL_SPLIT,

			split2,

			scrollForPanel2);

		add(split1);



		createPopupMenu();

	}



	public void createPopupMenu(){

		popup = new JPopupMenu();



		JMenuItem setting = new JMenuItem("設定");

		JMenuItem create = new JMenuItem("作成");

		JMenuItem copy = new JMenuItem("コピー");

		JMenuItem paste = new JMenuItem("貼り付け");

		JMenuItem delete = new JMenuItem("削除");



		popup.add(setting);

		popup.add(new JSeparator());

		popup.add(create);

		popup.add(new JSeparator());

		popup.add(copy);

		popup.add(paste);

		popup.add(delete);

	}

}