Theature Revenue

final double percent = .20;
double adultCost;
private JTextField k1;
private JTextField k2;
private JTextField k3;
private JTextField k4;
private JButton button;
private final int WINDOW_WIDTH = 600;
private final int WINDOW_HEIGHT = 400;

public Theater() {
	setTitle("Theater Revenue");
    setSize(WINDOW_WIDTH, WINDOW_HEIGHT);
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    setLayout(new GridLayout(5,2));
    button = new JButton("Revenue procss");
    button.addActionListener(new revenuecalc());

    JLabel label1 = new JLabel("Enter the price of one adult ticket : ");
    k1 = new JTextField(10);
    JLabel label3 = new JLabel("Enter the number of adult tickets sold : ");
    k2 = new JTextField(10);
    JLabel label5 = new JLabel("Enter the price of one child ticket : ");
    k3 = new JTextField(10);
    JLabel label7 = new JLabel("Enter the number of child tickets sold : ");
    k4 = new JTextField(10);

    JPanel p1 = new JPanel();
    JPanel p2 = new JPanel();
    JPanel p3 = new JPanel();
    JPanel p4 = new JPanel();
    JPanel p5 = new JPanel();
    JPanel p6 = new JPanel();
    JPanel p7 = new JPanel();
    JPanel p8 = new JPanel();
    JPanel p9 = new JPanel();

    p1.add(label1);
    p2.add(k1);
    p3.add(label3);
    p4.add(k2);
    p5.add(label5);
    p6.add(k3);
    p7.add(label7);
    p8.add(k4);
    p9.add(button);
    
    add(p1);
    add(p2);
    add(p3);
    add(p4);
    add(p5);
    add(p6);
    add(p7);
    add(p8);
    add(p9);
    setVisible(true);
    
}
private class revenuecalc implements ActionListener
{
	public void actionPerformed(ActionEvent e)
    {
        String priceticketadultperson;
        String soldpro;
        String priceticketchild;
        String soldc;
      
        priceticketadultperson = k1.getText();
        adultCost = Double.parseDouble(priceticketadultperson);
        System.out.println("answer");
        soldpro = k2.getText();
        double grossA1 = (adultCost) * Double.parseDouble(soldpro);
        double netAvalue = (grossA1) * percent;
        priceticketchild = k3.getText();
        soldc = k4.getText();
        double grossC1 = Double.parseDouble(priceticketchild)* Double.parseDouble(soldc);
        double netCvalue = grossC1 * percent;
        double totalGrossvalue = grossC1+grossA1;
        double totalNetvalue = netAvalue+netCvalue;
        JOptionPane.showMessageDialog(null, "Total gross adult revenue values : " + grossA1 + "\n" +"Total net value : " +
        netAvalue + "\n" +"Total gross child person value : " + grossC1 + "\n" +"Total netchild value : " +
        netCvalue + "\n" +"Total gross sales : " + totalGrossvalue + "\n" +"Total net sales : " + totalNetvalue);
}
}

public static void main(String[] args) {
	Theater theatre = new Theater();
}