蓝宇快递打印系统 打印快递单是怎么写的

    private JMenuItem getprintMI() {
        if (printMI == null) {
            printMI = new JMenuItem();
            printMI.setText("打印快递单");
            printMI.addActionListener(new java.awt.event.ActionListener() {
                public void actionPerformed(java.awt.event.ActionEvent e) {
                    PrintAndPrintSetFrame thisClass = new PrintAndPrintSetFrame();
                    thisClass.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
                    Toolkit tookit = thisClass.getToolkit();
                    Dimension dm = tookit.getScreenSize();
                    thisClass.setLocation(
                            (dm.width - thisClass.getWidth()) / 2,
                            (dm.height - thisClass.getHeight()) / 2);
                    thisClass.setVisible(true);
                }
            });
        }
        return printMI;
    }

请问一下这段是怎么写出来的 用的什么方法 急 谢谢了