GUI interface for TillSlip Program - Error free not running.

Hi there i am a beginner java programmer - the platform in which i am currently working with is java - NetBeans.
I have recently been working on a program that involves GUI. This current program involves using the JPannel Form in NetBeans.

The program that i am working on is to create a Till Slip using a graphical user interface - i have already done the design of the GUI and the necessary source codes required for it but the problem is that the program compiles and runs with no errors but nothing happens it keeps bringing up the message class "TillSlipUI" does not have a main method.

Below is the source code:

import java.util.*;
import java.text.*;
public class TillSlipUI extends javax.swing.JPanel {
    
    double num1;
    double num2;
    double num3;
    double totalItems;
    double vat;
    double finTotal;
    double amt;
    double change;
    
 DecimalFormat d = new DecimalFormat ("0.00");
    

    /**
     * Creates new form TillSlipUI
     */
    public TillSlipUI() {
        initComponents();
    }

    /**
     * This method is called from within the constructor to initialize the form.
     * WARNING: Do NOT modify this code. The content of this method is always
     * regenerated by the Form Editor.
     */
    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">                          
    private void initComponents() {

        jPanel1 = new javax.swing.JPanel();
        jLabel1 = new javax.swing.JLabel();
        jLabel2 = new javax.swing.JLabel();
        jLabel3 = new javax.swing.JLabel();
        totalButton = new javax.swing.JButton();
        vatButton = new javax.swing.JButton();
        finalTotButton = new javax.swing.JButton();
        jLabel4 = new javax.swing.JLabel();
        changeButton = new javax.swing.JButton();
        item1TxtFld = new javax.swing.JTextField();
        item2TxtFld = new javax.swing.JTextField();
        item3TxtFld = new javax.swing.JTextField();
        totalTxtFld = new javax.swing.JTextField();
        vatTxtFld = new javax.swing.JTextField();
        finalTotalTxtFld = new javax.swing.JTextField();
        amountTxtFld = new javax.swing.JTextField();
        changeTxtFld = new javax.swing.JTextField();

        jPanel1.setBackground(new java.awt.Color(153, 255, 255));
        jPanel1.setBorder(javax.swing.BorderFactory.createTitledBorder(null, "Till Slip", javax.swing.border.TitledBorder.DEFAULT_JUSTIFICATION, javax.swing.border.TitledBorder.DEFAULT_POSITION, new java.awt.Font("Brush Script MT", 1, 36), new java.awt.Color(0, 204, 0))); // NOI18N

        jLabel1.setText("Price of Item1");

        jLabel2.setText("Price of Item2");

        jLabel3.setText("Price of Item3");

        totalButton.setText("Total");
        totalButton.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                totalButtonActionPerformed(evt);
            }
        });

        vatButton.setText("VAT");
        vatButton.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                vatButtonActionPerformed(evt);
            }
        });

        finalTotButton.setText("Final Total");
        finalTotButton.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                finalTotButtonActionPerformed(evt);
            }
        });

        jLabel4.setText("Amount Tendered");

        changeButton.setText("Change");
        changeButton.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                changeButtonActionPerformed(evt);
            }
        });

        javax.swing.GroupLayout jPanel1Layout = new javax.swing.GroupLayout(jPanel1);
        jPanel1.setLayout(jPanel1Layout);
        jPanel1Layout.setHorizontalGroup(
            jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(jPanel1Layout.createSequentialGroup()
                .addContainerGap()
                .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addGroup(jPanel1Layout.createSequentialGroup()
                        .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING, false)
                            .addComponent(vatButton, javax.swing.GroupLayout.Alignment.LEADING, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                            .addComponent(totalButton, javax.swing.GroupLayout.Alignment.LEADING, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                            .addComponent(finalTotButton, javax.swing.GroupLayout.Alignment.LEADING, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
                        .addGap(0, 0, Short.MAX_VALUE))
                    .addComponent(changeButton, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                    .addComponent(jLabel4, javax.swing.GroupLayout.DEFAULT_SIZE, 88, Short.MAX_VALUE)
                    .addGroup(jPanel1Layout.createSequentialGroup()
                        .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                            .addComponent(jLabel3, javax.swing.GroupLayout.PREFERRED_SIZE, 80, javax.swing.GroupLayout.PREFERRED_SIZE)
                            .addComponent(jLabel2, javax.swing.GroupLayout.PREFERRED_SIZE, 80, javax.swing.GroupLayout.PREFERRED_SIZE)
                            .addComponent(jLabel1, javax.swing.GroupLayout.PREFERRED_SIZE, 80, javax.swing.GroupLayout.PREFERRED_SIZE))
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)))
                .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, jPanel1Layout.createSequentialGroup()
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                        .addComponent(item1TxtFld, javax.swing.GroupLayout.PREFERRED_SIZE, 200, javax.swing.GroupLayout.PREFERRED_SIZE))
                    .addGroup(jPanel1Layout.createSequentialGroup()
                        .addGap(31, 31, 31)
                        .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                            .addComponent(finalTotalTxtFld, javax.swing.GroupLayout.PREFERRED_SIZE, 200, javax.swing.GroupLayout.PREFERRED_SIZE)
                            .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING, false)
                                .addComponent(amountTxtFld)
                                .addComponent(changeTxtFld, javax.swing.GroupLayout.DEFAULT_SIZE, 200, Short.MAX_VALUE))
                            .addComponent(vatTxtFld, javax.swing.GroupLayout.PREFERRED_SIZE, 200, javax.swing.GroupLayout.PREFERRED_SIZE)
                            .addComponent(totalTxtFld, javax.swing.GroupLayout.PREFERRED_SIZE, 200, javax.swing.GroupLayout.PREFERRED_SIZE)
                            .addComponent(item3TxtFld, javax.swing.GroupLayout.PREFERRED_SIZE, 200, javax.swing.GroupLayout.PREFERRED_SIZE)
                            .addComponent(item2TxtFld, javax.swing.GroupLayout.PREFERRED_SIZE, 200, javax.swing.GroupLayout.PREFERRED_SIZE))))
                .addGap(425, 425, 425))
        );
        jPanel1Layout.setVerticalGroup(
            jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(jPanel1Layout.createSequentialGroup()
                .addGap(20, 20, 20)
                .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(jLabel1, javax.swing.GroupLayout.PREFERRED_SIZE, 22, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(item1TxtFld, javax.swing.GroupLayout.PREFERRED_SIZE, 22, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, 35, Short.MAX_VALUE)
                .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(jLabel2, javax.swing.GroupLayout.PREFERRED_SIZE, 22, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(item2TxtFld, javax.swing.GroupLayout.PREFERRED_SIZE, 22, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addGap(30, 30, 30)
                .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(jLabel3, javax.swing.GroupLayout.PREFERRED_SIZE, 22, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(item3TxtFld, javax.swing.GroupLayout.PREFERRED_SIZE, 22, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addGap(45, 45, 45)
                .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(totalButton)
                    .addComponent(totalTxtFld, javax.swing.GroupLayout.PREFERRED_SIZE, 23, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addGap(33, 33, 33)
                .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(vatButton)
                    .addComponent(vatTxtFld, javax.swing.GroupLayout.PREFERRED_SIZE, 23, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addGap(40, 40, 40)
                .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(finalTotButton)
                    .addComponent(finalTotalTxtFld, javax.swing.GroupLayout.PREFERRED_SIZE, 23, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addGap(26, 26, 26)
                .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(jLabel4, javax.swing.GroupLayout.PREFERRED_SIZE, 22, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(amountTxtFld, javax.swing.GroupLayout.PREFERRED_SIZE, 22, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addGap(33, 33, 33)
                .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(changeButton)
                    .addComponent(changeTxtFld, javax.swing.GroupLayout.PREFERRED_SIZE, 23, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addGap(23, 23, 23))
        );

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(this);
        this.setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
                .addContainerGap()
                .addComponent(jPanel1, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                .addContainerGap())
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addContainerGap()
                .addComponent(jPanel1, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                .addContainerGap())
        );
    }// </editor-fold>                        

    private void totalButtonActionPerformed(java.awt.event.ActionEvent evt) {                                            
    num1 = Double.parseDouble(item1TxtFld.getText()); 
    num2 = Double.parseDouble(item2TxtFld.getText());
    num3 = Double.parseDouble(item3TxtFld.getText());
    totalItems = num1 + num2 + num3;
    totalTxtFld.setText(""+d.format(totalItems));
    item1TxtFld.setText("");
    item2TxtFld.setText("");
    item3TxtFld.setText("");
    amountTxtFld.setText("");
    }                                           

    private void vatButtonActionPerformed(java.awt.event.ActionEvent evt) {                                          
        vat = totalItems*14/100;
        vatTxtFld.setText(""+d.format(vat));
        vatTxtFld.setText("");
    }                                         

    private void finalTotButtonActionPerformed(java.awt.event.ActionEvent evt) {                                               
      finTotal = totalItems + vat;
      finalTotalTxtFld.setText(""+d.format(finTotal));
    }                                              

    private void changeButtonActionPerformed(java.awt.event.ActionEvent evt) {                                             
        amt = Double.parseDouble(amountTxtFld.getText());
        change = amt - finTotal;
        changeTxtFld.setText(""+d.format(change));
    }                                            

    // Variables declaration - do not modify                     
    private javax.swing.JTextField amountTxtFld;
    private javax.swing.JButton changeButton;
    private javax.swing.JTextField changeTxtFld;
    private javax.swing.JButton finalTotButton;
    private javax.swing.JTextField finalTotalTxtFld;
    private javax.swing.JTextField item1TxtFld;
    private javax.swing.JTextField item2TxtFld;
    private javax.swing.JTextField item3TxtFld;
    private javax.swing.JLabel jLabel1;
    private javax.swing.JLabel jLabel2;
    private javax.swing.JLabel jLabel3;
    private javax.swing.JLabel jLabel4;
    private javax.swing.JPanel jPanel1;
    private javax.swing.JButton totalButton;
    private javax.swing.JTextField totalTxtFld;
    private javax.swing.JButton vatButton;
    private javax.swing.JTextField vatTxtFld;
    // End of variables declaration                   
}

I have taken the necessary arragenments to ensure all factors such as variable names of components are correct.
I have no idea how to sort this problem out - i will really appreciate it your guys would really help me out on this one - Thanks Alot!