How to add data from MySQL database to JComboBox in Java Swing?

 

GUI

package Trial;

import java.awt.Font;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;

import javax.swing.JButton;
import javax.swing.JCheckBox;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JOptionPane;

class Demo {

	JButton jb1;
	JCheckBox cb1, cb2, cb3;
	JComboBox comRoomNo;

	Demo() {
		JFrame frame = new JFrame();
		frame.setTitle("Hancie e-Learning Studio");
		frame.setLayout(null);
		frame.setSize(600, 500);
		frame.setLocationRelativeTo(null);

		comRoomNo = new JComboBox();
		comRoomNo.setBounds(159, 23, 206, 34);
		frame.add(comRoomNo);
		comRoomNo.setFont(new Font("Times New Roman", Font.PLAIN, 16));

		try {

			Class.forName("com.mysql.cj.jdbc.Driver");
			Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/" + 
			"hotel_database", "root",
					"");

			String query1 = "select customers.Customer_ID, customers.Name,"
					+ " booking.Booking_ID, booking.CheckIn, booking.CheckOut,"
					+ " booking.Room_ID,booking.Booking_Type, booking.Booking_Status"
					+ " from booking left join customers on booking.Customer_ID = " +
					"customers.Customer_ID;";

			PreparedStatement pst1 = conn.prepareStatement(query1);
			ResultSet rst1 = pst1.executeQuery();

			String Booking_ID = "";
			while (rst1.next()) {

				comRoomNo.addItem(rst1.getString("Booking_ID"));
			}

		} catch (Exception ex) {
			JOptionPane.showMessageDialog(null, ex);
		}

		frame.setVisible(true);

	}

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

Output