JLabel在

Question

输入并按下按钮后，JLabel的“结果”不会出现

public class qes{
    static String special1;


public static void Count(double a, double b, double c) {
    Double d = (b*b) - (4 * a * c);
    Double temp = Math.sqrt(d);
    Double res1 = (-b + temp)/(2*a);
    Double res2 = (-b - temp)/(2*a);
    String res = "x1 = " + res1 + " x2 = " + res2;
    special1 = res;
}

public static void main(String[] args){
    String path = "C:\\SPC\\res\\bckg.jpg";
    String font = "Calibri";
    String path1 = "C:\\SPC\\res\\close1.png";
    int size = 24;
    int size1 = 36;


    JFrame wndw1 = new JFrame("Quadratic Equations Solver");
    wndw1.setUndecorated(true);
    wndw1.setExtendedState(JFrame.MAXIMIZED_BOTH);
    wndw1.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    JLabel bckg = new JLabel(new ImageIcon(path));
    wndw1.setContentPane(bckg);
    JTextField first = new JTextField();
        first.setEditable(true);
        first.setFont(new Font(font, Font.PLAIN, size));
        first.setBounds(600, 400, 50, 50);
        first.setVisible(true);
        bckg.add(first);

        JLabel txt1 = new JLabel("X\u00B2 +");
        txt1.setFont(new Font(font, Font.PLAIN, size1));
        txt1.setBounds(655, 400, 60, 50);
        txt1.setVisible(true);
        bckg.add(txt1);

        JTextField second = new JTextField();
        second.setEditable(true);
        second.setFont(new Font(font, Font.PLAIN, size));
        second.setBounds(720, 400, 50, 50);
        second.setVisible(true);
        bckg.add(second);

        JLabel txt2 = new JLabel("X +");
        txt2.setFont(new Font(font, Font.PLAIN, size1));
        txt2.setBounds(775, 400, 50, 50);
        txt2.setVisible(true);
        bckg.add(txt2);

        JTextField third = new JTextField();
        third.setEditable(true);
        third.setFont(new Font(font, Font.PLAIN, size));
        third.setBounds(830, 400, 50, 50);
        third.setVisible(true);
        bckg.add(third);

        JLabel txt3 = new JLabel("= 0");
        txt3.setFont(new Font(font, Font.PLAIN, size1));
        txt3.setBounds(885, 400, 50, 50);
        txt3.setVisible(true);
        bckg.add(txt3);

        JButton but = new JButton("Calculate equation roots");
        but.setFont(new Font(font, Font.PLAIN, size));
        but.setBounds(620, 550, 280, 80);
        but.setVisible(true);
        but.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent f){
                Double x = Double.parseDouble(first.getText());
                Double y = Double.parseDouble(second.getText());
                Double z = Double.parseDouble(third.getText());
                qes.Count(x, y, z);

                JLabel result = new JLabel(special1);
                result.setFont(new Font(font, Font.PLAIN, size1));
                result.setBounds(200, 700, 500, 100);
                result.setForeground(Color.BLACK);
                result.setVisible(true);
                bckg.add(result);
            }
        });
        bckg.add(but);

        wndw1.setVisible(true);
    }

}

我个人在这里看不到任何错误 而且我没有收到任何警告 也。我只填写 附言另外，当我尝试写那个：

if(x == null){
    x = 1;
}

我收到警告，说这是无效代码

P.P.S。而且，我很乐意得到有关我的代码的任何建议

P.P.P.S我写了这一行和上一行，只是因为Stack Overflow不允许发布带有大量代码和少量文本的问题，我无话可说