pertambahan sederhana

package javaapplication19;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.*;
class clickBoss implements ActionListener{
    int cc;
    String hasil;
    private Main badal ;
    public clickBoss(Main ccc){
        this.badal = ccc ;
    }
    public void actionPerformed(ActionEvent e) {
        String a = this.badal.kl.getSelectedItem().toString();
        int vv;
        String hsil;
        Component panel = null;
        if(a.equals("perkalian")){
         String aaa = this.badal.txtawal.getText();
        int fff =Integer.parseInt(aaa);
        String bbb = this.badal.txtsani.getText();
        int ggg =Integer.parseInt(bbb);
        vv = fff * ggg;
        hsil = Integer.toString(vv);
        this.badal.txthasil.setText(hsil);
        }
        else if(a.equals("pembagian")){
             String aaa = this.badal.txtawal.getText();
             int fff =Integer.parseInt(aaa);
             String bbb = this.badal.txtsani.getText();
             int ggg =Integer.parseInt(bbb);
             if(ggg == 0){
                 JOptionPane.showMessageDialog(panel, "Oopz gagal...???? ",
                         "Error", JOptionPane.ERROR_MESSAGE);
                 return;
             }
             vv = fff / ggg;
             hsil= Integer.toString(vv);
             this.badal.txthasil.setText(hsil);
        }
        else if(a.equals("pertambahan")){
             String aaa = this.badal.txtawal.getText();
             int fff =Integer.parseInt(aaa);
             String bbb = this.badal.txtsani.getText();
             int ggg =Integer.parseInt(bbb);
             vv = fff + ggg;
             hsil = Integer.toString(vv);
             this.badal.txthasil.setText(hsil);
        }
        else if(a.equals("pengurangan")){
            String aaa = this.badal.txtawal.getText();
            int fff =Integer.parseInt(aaa);
            String bbb = this.badal.txtsani.getText();
            int ggg =Integer.parseInt(bbb);
            vv = fff - ggg;
            hsil= Integer.toString(vv);
            this.badal.txthasil.setText(hsil);
        }
        else{
            JOptionPane.showMessageDialog(badal, "jkasjkhajshnjash ",
                    "Error", JOptionPane.ERROR_MESSAGE);
        }
    }
}

public class Main extends JFrame{
 ActionListener guyz = new ActionListener() {
        private Component panel;
        public void actionPerformed(ActionEvent actionEvent) {
    JDialog.setDefaultLookAndFeelDecorated(true);
    int response = JOptionPane.showConfirmDialog(null, "apakah anda yakin ingin keluar ?", "OOppzz",
        JOptionPane.YES_NO_OPTION, JOptionPane.QUESTION_MESSAGE);
    if (response == JOptionPane.NO_OPTION) {
      System.out.println("No button clicked");
    } else if (response == JOptionPane.YES_OPTION) {
        System.exit(0);
    } else if (response == JOptionPane.CLOSED_OPTION) {

    }
      }
    };
    String [] ahay ={"perkalian","pembagian","pertambahan","pengurangan"};
    private Label lblawal = new Label("pertama");
    private Label lblsani = new Label("kedua:");
    private Label lblhasil = new Label("hasil");
    private Label lblJK = new Label("pilihan");
    private JButton btnOK = new JButton("OK");
    private JButton btnCancel = new JButton("Quit");

    public JTextField txtawal = new JTextField();
    public JTextField txtsani = new JTextField();
    public JTextField txthasil = new JTextField();
    public JComboBox kl = new JComboBox(ahay);

    public Main(){
        super("i-Team Of Fatihul Ulum");
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setLocation(100,100);
        setSize(400,200);

        lblawal.setAlignment(Label.RIGHT);
        lblsani.setAlignment(Label.RIGHT);
        lblhasil.setAlignment(Label.RIGHT);
        lblJK.setAlignment(Label.RIGHT);

        JPanel pan = new JPanel();
        pan.setLayout(new GridLayout(6,3));
        pan.add(this.lblJK);
        pan.add(kl);
        pan.add(this.lblawal);
        pan.add(this.txtawal);
        pan.add(this.lblsani);
        pan.add(this.txtsani);
        pan.add(this.lblhasil);
        pan.add(this.txthasil);
        pan.add(btnOK);
        this.btnOK.addActionListener(new clickBoss(this));
        pan.add(btnCancel);
        this.btnCancel.addActionListener(guyz);
        pan.setBorder(BorderFactory.createEmptyBorder(10,25,15, 5));
        this.add(pan);
       setVisible(true);
    }
    public static void main(String [] args){
        new Main();
    }
}