パネルが独自のカーソルを設定するときに Java 待機カーソルが表示されないのはなぜですか?

public class BusyCursorTest extends javax.swing.JFrame {

    private javax.swing.JPanel cursorPanel = null;

    public BusyCursorTest() {
        // ...
        // Set the wait cursor on the glass pane
        startWaitCursor(this);
        // ...
    }

    private static void startWaitCursor(javax.swing.JFrame frame) {
        frame.getGlassPane().setCursor(java.awt.Cursor.getPredefinedCursor(java.awt.Cursor.WAIT_CURSOR));
        // Add mouse listener to glass pane for handling cursor visibility
        frame.getGlassPane().addMouseListener(mouseAdapter);
        frame.getGlassPane().setVisible(true);
    }

    // ...

    private static java.awt.event.MouseAdapter mouseAdapter = new java.awt.event.MouseAdapter() {
    };
}