JAVA GUI : Coba ComboBox

// paket yang diperlukan
import javax.swing.*;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;

class TestComboBox extends JFrame{
    // attribut
    //membuat tombol
    JButton tombol1 = new JButton("ambil nilai");
    JButton tombol2 = new JButton("set nilai Combobox");
    JLabel label = new JLabel("nilai Combobox");
    // JComboBox(String nama)
    String[] menu = {"Nasi","Ayam","Goreng"};
    JComboBox cb = new JComboBox(menu);

    //konstruktor
    public TestComboBox(){
        //frame seting---------------------------------------------------------------------
        //memanggil konstruktor kelas induk (JFrame)
        super("Contoh Combobox");
        //seting besar frame 400 x 400 px
        this.setSize(200,200);
        //seting agar bisa ditutup
        this.setDefaultCloseOperation(EXIT_ON_CLOSE);
        //seting kemunculan frame di tengah window
        this.setLocationRelativeTo(null);
        //seting layout frame
        this.getContentPane().setLayout(null);
        //frame seting---------------------------------------------------------------------
        //menambahkan komponen ke frame dan seting letak
        this.add(tombol1);
        this.add(tombol2);
        this.add(label);
        this.add(cb);
        // setbounds(x,y,lebar,tinggi)
        tombol1.setBounds(10,10,150,25);
        tombol2.setBounds(10,40,150,25);
        label.setBounds(10,70,150,25);
        cb.setBounds(10,110,150,25);
        //seting aksi tombol
        tombol1.addActionListener(new ActionListener( ) {
            public void actionPerformed(ActionEvent e){
                // kode disini; cek keadaan check box
                int i = cb.getSelectedIndex();
                String str = "";
                switch(i){
                    case 0: str = "anda mau makan "+menu[i]; break;
                    case 1: str = "anda makan "+menu[i]+" bakar"; break;
                    case 2: str = menu[i]+" bakwan"; break;
                }
                label.setText(str);
            }
        });
        tombol2.addActionListener(new ActionListener( ) {
            public void actionPerformed(ActionEvent e){
                // kode disini; cek keadaan check box ganti keadaan chek box
                cb.setSelectedIndex(2);
                label.setText("anda memilih index-2");
            }
        });
        // menampilkan frame
        show();

    }

    public static void main(String[] args){
        new TestComboBox();
    }
}