Java JComboBox class

JComboBox is like a drop down box — you can click a drop-down arrow and select an option from a list. It generates ItemEvent. For example, when the component has focus, pressing a key that corresponds to the first character in some entry’s name selects that entry. A vertical scrollbar is used for longer lists.

JComboBox Source Code

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

public class JComboBoxDemo extends JPanel {

	JLabel jlbPicture;
	public JComboBoxDemo() {
		String[] comboTypes = { "Numbers", "Alphabets", "Symbols" };
		// Create the combo box, and set 2nd item as Default
		JComboBox comboTypesList = new JComboBox(comboTypes);
		comboTypesList.setSelectedIndex(2);
		comboTypesList.addActionListener(new ActionListener() {

			public void actionPerformed(ActionEvent e) {
				JComboBox jcmbType = (JComboBox) e.getSource();
				String cmbType = (String) jcmbType.getSelectedItem();
				jlbPicture.setIcon(new ImageIcon(""
						+ cmbType.trim().toLowerCase() + ".jpg"));
			}
		});
		// Set up the picture
		jlbPicture = new JLabel(new ImageIcon(""
				+ comboTypes[comboTypesList.getSelectedIndex()] + ".jpg"));
		jlbPicture.setBorder(BorderFactory.createEmptyBorder(10, 0, 0, 0));

		jlbPicture.setPreferredSize(new Dimension(177, 122 + 10));
		// Layout the demo
		setLayout(new BorderLayout());
		add(comboTypesList, BorderLayout.NORTH);
		add(jlbPicture, BorderLayout.SOUTH);
		setBorder(BorderFactory.createEmptyBorder(20, 20, 20, 20));
	}
	public static void main(String s[]) {
		JFrame frame = new JFrame("JComboBox Usage Demo");
		frame.addWindowListener(new WindowAdapter() {

			public void windowClosing(WindowEvent e) {
				System.exit(0);
			}
		});
		frame.setContentPane(new JComboBoxDemo());
		frame.pack();
		frame.setVisible(true);
	}
}