Tạo 1 menu bar đơn giản .
Tại sao nó cứ báo lỗi không load được hàm main?? ai giúp mình với

Mã:
package baiawt1;

import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JFrame;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;





public class MenuDemo extends JFrame implements ActionListener{
	
	
	public  MenuDemo(){
		setSize(300, 300);
		setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		java.awt.Container contentPane = getContentPane();
		contentPane.setLayout(new FlowLayout());


		JMenu colorMenu = new JMenu("Colors");
		JMenuItem item;
		item = new JMenuItem("Red");
		item.addActionListener((ActionListener) this);
		colorMenu.add(item);
		item = new JMenuItem("Orange");
		item.addActionListener(this);
		colorMenu.add(item);
		item = new JMenuItem("Green");
		item.addActionListener(this);
		colorMenu.add(item);
		JMenuBar menus = new JMenuBar();
		menus.add(colorMenu);
		setJMenuBar(menus); 
	}

	public void actionPerformed(ActionEvent e) {
		
		java.awt.Container contentPane = getContentPane();
		
		if (e.getActionCommand().equals("Red")){
			contentPane.setBackground(Color.red);
		}
		else 
			if (e.getActionCommand().equals("Orange")){
				contentPane.setBackground(Color.orange);
			}
			else 
				if (e.getActionCommand().equals("Green")){
					contentPane.setBackground(Color.green);
				}
	}
	
	public static void main(String[] args) {
		MenuDemo menuGui = new MenuDemo();
		menuGui.setVisible(true);
	}
}