请教一个jbuilder6的问题

Question

用这个函数，在主窗口的构造函数中调用
CenterScreen（this);把这个函数加到程序中：
void CenterScreen(JFrame frame)
    {
        Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
        frame.setSize(screenSize.width, screenSize.height-20);
        Dimension frameSize = frame.getSize();
        if(frameSize.height > screenSize.height)
        {
            frameSize.height = screenSize.height;
        }
        if(frameSize.width > screenSize.width)
        {
            frameSize.width = screenSize.width;
        }        frame.setLocation((screenSize.width-frameSize.width)/2, (screenSize.height-frameSize.height)/2-10);
        frame.setVisible(true);
    }