Point Of Sales

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;

public class Main {
    JFrame frame = null;
    JPanel panel = null;
    JTextField txtPetugasKasir = null;
    JTextField txtKodeBarang = null;
    JTextField txtNamaBarang = null;
    JTextField txtHarga = null;
    JTextField txtJumlahPembelian = null;
    JTextField txtTotalHarga = null;

    JFrame frameSubmit = null;
    JPanel panelSubmit = null;

    public static void main(String[] args){
        Main gui = new Main();
        gui.go();
    }

    public void go(){
        frame = new JFrame();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        panel = new JPanel();

        JLabel lblPetugasKasir = new JLabel("Kasir:");
        txtPetugasKasir = new JTextField(20);

        JLabel lblKodeBarang = new JLabel("Kode Barang:");
        txtKodeBarang = new JTextField(20);

        JLabel lblNamaBarang = new JLabel("Nama Barang:");
        txtNamaBarang = new JTextField(20);

        JLabel lblHarga = new JLabel("Harga:");
        txtHarga = new JTextField(20);
        txtHarga.setText("0");
        txtHarga.getDocument().addDocumentListener(new DocumentListener() {
            public void changedUpdate(DocumentEvent e) {
                warn();
            }
            public void removeUpdate(DocumentEvent e) {
                warn();
            }
            public void insertUpdate(DocumentEvent e) {
                warn();
            }

            public void warn() {
                int harga = Integer.parseInt(txtHarga.getText());
                int jumlahPembelian = Integer.parseInt(txtJumlahPembelian.getText());
                int totalHarga = harga * jumlahPembelian;
                txtTotalHarga.setText("" + totalHarga);
            }
        });

        JLabel lblJumlahPembelian = new JLabel("Jumlah Pembelian:");
        txtJumlahPembelian = new JTextField(20);
        txtJumlahPembelian.setText("0");
        txtJumlahPembelian.getDocument().addDocumentListener(new DocumentListener() {
            public void changedUpdate(DocumentEvent e) {
                warn();
            }
            public void removeUpdate(DocumentEvent e) {
                warn();
            }
            public void insertUpdate(DocumentEvent e) {
                warn();
            }

            public void warn() {
                int harga = Integer.parseInt(txtHarga.getText());
                int jumlahPembelian = Integer.parseInt(txtJumlahPembelian.getText());
                int totalHarga = harga * jumlahPembelian;
                txtTotalHarga.setText("" + totalHarga);
            }
        });

        JLabel lblTotalHarga = new JLabel("Total Harga:");
        txtTotalHarga = new JTextField(20);

        JButton btnSubmit = new JButton("Cetak");
        btnSubmit.addActionListener(new SubmitListener(this));

        panel.add(lblPetugasKasir);
        panel.add(txtPetugasKasir);
        panel.add(lblKodeBarang);
        panel.add(txtKodeBarang);
        panel.add(lblNamaBarang);
        panel.add(txtNamaBarang);
        panel.add(lblHarga);
        panel.add(txtHarga);
        panel.add(lblJumlahPembelian);
        panel.add(txtJumlahPembelian);
        panel.add(lblTotalHarga);
        panel.add(txtTotalHarga);

        panel.add(btnSubmit);
        frame.getContentPane().add(BorderLayout.CENTER,panel);

        frame.setSize(250,500);
        frame.setVisible(true);
    }

    public void sendMessage(String msg) {
        JOptionPane.showMessageDialog(null,msg);
    }

    public void showSubmitBarang(Main view) {
        String petugasKasir = view.txtPetugasKasir.getText();
        String kodeBarang = view.txtKodeBarang.getText();
        String namaBarang = view.txtNamaBarang.getText();
        String harga = view.txtHarga.getText();
        String jumlahPembelian = view.txtJumlahPembelian.getText();
        int totalHarga = Integer.parseInt(harga) * Integer.parseInt(jumlahPembelian);

        view.frame.setVisible(false);
        view.frameSubmit = new JFrame();
        view.frameSubmit.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        view.panelSubmit = new JPanel();

        JLabel lblPembelian = new JLabel("Pembelian");
        JLabel lblNamaBarang = new JLabel("" + namaBarang + " x" + jumlahPembelian);
        JLabel lblTotalBayar = new JLabel("Total Bayar: Rp." + totalHarga);

        view.panelSubmit.add(lblPembelian);
        view.panelSubmit.add(lblNamaBarang);
        view.panelSubmit.add(lblTotalBayar);

        view.frameSubmit.getContentPane().add(BorderLayout.CENTER,view.panelSubmit);

        view.frameSubmit.setSize(210,500);
        view.frameSubmit.setVisible(true);

    }

    public class SubmitListener implements ActionListener{
        Main view;

        public SubmitListener(Main view) {
            this.view = view;
        }

        public void actionPerformed(ActionEvent event){
            view.showSubmitBarang(view);
        }
    }
}