class Demo {
    public static void main(String[] args) throws Exception {
        JFrame frame = new JFrame();
        frame.setLayout(new FlowLayout());
        frame.setSize(300, 300);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);


        MaskFormatter mask = new MaskFormatter("########/##");
        JFormattedTextField txtName = new JFormattedTextField();
        mask.install(txtName);

        frame.add(txtName);

        JButton button = new JButton("click me");
        button.addActionListener((e)-> {
            System.out.println(txtName.getText());
        });
        frame.add(button);
        frame.setVisible(true);
    }
}