ComboBox Dinamis Java Swing

FrameComboDinamis.java

import java.awt.EventQueue;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.UnsupportedLookAndFeelException;
import javax.swing.border.EmptyBorder;
import javax.swing.ImageIcon;
import javax.swing.JComboBox;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JTextField;
import javax.swing.JButton;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import java.awt.Color;

@SuppressWarnings("serial")
public class FrameComboDinamis extends JFrame 
{

	private JPanel contentPane;
	@SuppressWarnings("rawtypes")
	private JComboBox cbJudulBuku;
	String judul[] = {"Java Programming with GUI Make Over","Do'a Membawa Berkah","Jaga Mata, Jaga Telinga, Jaga Mulut"};
	private JTextField txtId;
	private JLabel lblIdBuku;
	private JLabel lblJudulbuku;
	private JLabel lblPenerbit;
	private JTextField txtPenerbit;
	String id,judulBuku,penerbit;
	private JLabel lblIcon;
	private JLabel lblIcon_2;
	/**
	 * Create the frame.
	 */
	public FrameComboDinamis() 
	{
		setResizable(false);
		setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		setBounds(100, 100, 610, 341);
		contentPane = new JPanel();
		contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
		setContentPane(contentPane);
		contentPane.setLayout(null);
		
		cbJudulBuku = new ModifyComboBox(judul);
		cbJudulBuku.setBounds(116, 55, 155, 24);
		contentPane.add(cbJudulBuku);
		
		lblIdBuku = new JLabel("ID Buku : ");
		lblIdBuku.setForeground(new Color(255, 255, 255));
		lblIdBuku.setBounds(12, 12, 70, 18);
		contentPane.add(lblIdBuku);
		
		lblJudulbuku = new JLabel("JudulBuku : ");
		lblJudulbuku.setForeground(new Color(255, 255, 255));
		lblJudulbuku.setBounds(12, 58, 93, 18);
		contentPane.add(lblJudulbuku);
		
		txtId = new JTextField();
		txtId.setBounds(116, 8, 149, 27);
		contentPane.add(txtId);
		txtId.setColumns(10);
		
		lblPenerbit = new JLabel("Penerbit : ");
		lblPenerbit.setForeground(new Color(255, 255, 255));
		lblPenerbit.setBounds(12, 101, 80, 15);
		contentPane.add(lblPenerbit);
		
		txtPenerbit = new JTextField();
		txtPenerbit.setBounds(116, 95, 301, 27);
		contentPane.add(txtPenerbit);
		txtPenerbit.setColumns(10);
		
		JButton btnTampilkan = new JButton("Tampilkan");
		btnTampilkan.setIcon(new ImageIcon("/home/resa/Aplikasi Java/SwingComponents/src/Gambar/tampilData.png"));
		btnTampilkan.addActionListener(new ActionListener()
		{
			public void actionPerformed(ActionEvent act) 
			{
				id = txtId.getText();
				if(cbJudulBuku.getSelectedIndex() == 0)
				{
					judulBuku = "Java Programming with GUI Make Over";
				}
				else if(cbJudulBuku.getSelectedIndex() == 1)
				{
					judulBuku = "Do'a Membawa Berkah";
				}
				if(cbJudulBuku.getSelectedIndex() == 2)
				{
					judulBuku = "Jaga Mata, Jaga Telinga, Jaga Mulut";
				}
				penerbit = txtPenerbit.getText();
				
				JOptionPane.showMessageDialog(null,"ID Buku : " + id + "\n" + "Judul Buku : " + judulBuku + "\n" + "Penerbit : " + penerbit,"Pesan",JOptionPane.INFORMATION_MESSAGE,new ImageIcon("src/Gambar/success.png"));
			}
		});
		btnTampilkan.setBounds(149, 196, 125, 38);
		contentPane.add(btnTampilkan);
		
		JButton btnNewButton = new JButton("Refresh");
		btnNewButton.setIcon(new ImageIcon("/home/resa/Aplikasi Java/SwingComponents/src/Gambar/refresh.png"));
		btnNewButton.addActionListener(new ActionListener()
		{
			public void actionPerformed(ActionEvent act) 
			{
				txtId.setText("");
				cbJudulBuku.setSelectedIndex(0);
				txtPenerbit.setText("");
				txtId.requestFocus();
			}
		});
		btnNewButton.setBounds(286, 196, 125, 38);
		contentPane.add(btnNewButton);
		
		lblIcon = new JLabel("");
		lblIcon.setIcon(new ImageIcon("/home/resa/Aplikasi Java/SwingComponents/src/Gambar/buku.png"));
		lblIcon.setBounds(454, 41, 136, 142);
		contentPane.add(lblIcon);
		
		lblIcon_2 = new JLabel("");
		lblIcon_2.setIcon(new ImageIcon("/home/resa/Aplikasi Java/SwingComponents/src/Gambar/pencil.png"));
		lblIcon_2.setBounds(12, 197, 125, 98);
		contentPane.add(lblIcon_2);
		
		JLabel lblBg = new JLabel("");
		lblBg.setIcon(new ImageIcon("/home/resa/Aplikasi Java/SwingComponents/src/Gambar/bgBlur.png"));
		lblBg.setBounds(0, 0, 608, 314);
		contentPane.add(lblBg);
		setLocationRelativeTo(null);
	}
	
	/**
	 * Launch the application.
	 */
	public static void main(String[] args) 
	{
		EventQueue.invokeLater(new Runnable()
		{
			public void run() 
			{
				for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
				    if ("com.sun.java.swing.plaf.gtk.GTKLookAndFeel".equals(info.getClassName())) {   
				       try 
				       {
						javax.swing.UIManager.setLookAndFeel(info.getClassName());
						FrameComboDinamis frame = new FrameComboDinamis();
						frame.setVisible(true);
				       } 
				       catch (ClassNotFoundException e) {
						// TODO Auto-generated catch block
						e.printStackTrace();
					} catch (InstantiationException e) {
						// TODO Auto-generated catch block
						e.printStackTrace();
					} catch (IllegalAccessException e) {
						// TODO Auto-generated catch block
						e.printStackTrace();
					} catch (UnsupportedLookAndFeelException e) {
						// TODO Auto-generated catch block
						e.printStackTrace();
					}
				       break;
				     } 
				}
			
			}
		});
	}
}

ModifyComboBox.java

import java.awt.Component;
import java.awt.Dimension;
import javax.swing.JComboBox;
import javax.swing.JList;

@SuppressWarnings({ "serial", "rawtypes" })
public class ModifyComboBox extends JComboBox 
{
	@SuppressWarnings("unchecked")
	public ModifyComboBox(String[] param)
	{
		super(param);
	}
	
	public Dimension getSize()
	{
		Dimension dimensi = super.getSize();
		int wide = getLebarCombo();
		dimensi.width = Math.max(wide, dimensi.width);
		
		return dimensi;
	}
	
	public int getLebarCombo()
	{
		int l = 0;
		int a;
		
		for(a=0;a<this.getItemCount();a++)
		{
			@SuppressWarnings("unchecked")
			Component komponen = this.getRenderer().getListCellRendererComponent(new JList(this.getModel()), this.getItemAt(a), a, false, false); 
			//(JList<? extends E> list, E value,int index,boolean isSelected,boolean cellHasFocus)
			l = Math.max(l, komponen.getPreferredSize().width);
		}
		return l + 10; //Margin lebar combo ditambah 10
	}
	
	
}