为什么jtable不透明？

Question

我自己教授JTable，并且我正在使用Oracle网站上的示例。 我试图修改它以便我可以使JTable透明，所以我应该能够看到下面的黄色背景，但它只显示白色。有什么想法吗？

请有人指出我正确的方向，我已尝试过谷歌的众多解决方案。

public class Test extends JPanel {

    private boolean DEBUG = false;

    public Test() {

        super(new GridLayout(1, 0));

        String[] columnNames = {"First Name",
            "Last Name",
            "Sport",
            "# of Years",
            "Vegetarian"};

        Object[][] data = {
            {"Kathy", "Smith",
                "Snowboarding", new Integer(5), new Boolean(false)},
            {"John", "Doe",
                "Rowing", new Integer(3), new Boolean(true)},
            {"Sue", "Black",
                "Knitting", new Integer(2), new Boolean(false)},
            {"Jane", "White",
                "Speed reading", new Integer(20), new Boolean(true)},
            {"Joe", "Brown",
                "Pool", new Integer(10), new Boolean(false)}
        };

        final JTable table = new JTable(data, columnNames);
        table.setPreferredScrollableViewportSize(new Dimension(322, 14));
        table.setFillsViewportHeight(true);
           table.setOpaque(false);
((DefaultTableCellRenderer)table.getDefaultRenderer(Object.class)).setOpaque(false);


        //Create the scroll pane and add the table to it.
        JScrollPane scrollPane = new JScrollPane(table);
        scrollPane.setColumnHeader(new JViewport());
        scrollPane.getColumnHeader().setOpaque(false);
        scrollPane.setOpaque(false);

        setBackground(Color.yellow);
        add(scrollPane);
    }

    private void printDebugData(JTable table) {
        int numRows = table.getRowCount();
        int numCols = table.getColumnCount();
        javax.swing.table.TableModel model = table.getModel();

        System.out.println("Value of data: ");
        for (int i = 0; i < numRows; i++) {
            System.out.print("    row " + i + ":");
            for (int j = 0; j < numCols; j++) {
                System.out.print("  " + model.getValueAt(i, j));
            }
            System.out.println();
        }
        System.out.println("--------------------------");
    }

    /**
     * Create the GUI and show it. For thread safety, this method should be
     * invoked from the event-dispatching thread.
     */
    private static void createAndShowGUI() {
        //Create and set up the window.
        JFrame frame = new JFrame("SimpleTableDemo");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        //Create and set up the content pane.
        Test newContentPane = new Test();
        newContentPane.setOpaque(true); //content panes must be opaque
        frame.setContentPane(newContentPane);

        //Display the window.
        frame.setBackground(Color.yellow);

        frame.pack();
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        //Schedule a job for the event-dispatching thread:
        //creating and showing this application's GUI.
        javax.swing.SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                createAndShowGUI();
            }
        });
    }
}