Problema com actionPerformed

import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
import javax.swing.JOptionPane;
public class LoginAccess extends JFrame implements ActionListener{
	JButton entrar, cancelar;
	public LoginAccess(){
		super("Login");
		this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		
		Container c = this.getContentPane();
		GridBagConstraints cons = new GridBagConstraints();
		GridBagLayout layout = new GridBagLayout();
		c.setLayout(layout);
		cons.insets = new Insets(5,5,5,5);
		
		cons.gridy = 0;
		cons.gridx = 0;
		cons.fill = GridBagConstraints.BOTH;
		c.add(new JLabel("Usuário"), cons);
		
		cons.gridy = 0;
		cons.gridx = 1;
		cons.gridwidth = 4;
		c.add(new JTextField(15),cons);
		
		cons.gridy = 1;
		cons.gridx = 0;
		cons.fill = GridBagConstraints.BOTH;
		cons.anchor = GridBagConstraints.CENTER;
		c.add(new JLabel("Senha"), cons);
		
		cons.gridy = 1;
		cons.gridx = 2;
		cons.gridwidth = 4;
		c.add(new JPasswordField(15),cons);
		
		cons.gridy = 2;
		cons.gridx = 1;
		cons.gridwidth = 2;
		c.add(entrar = new JButton("       OK     "), cons);
		
		cons.gridy = 2;
		cons.gridx = 3;
		cons.gridwidth = 2;
	    c.add(cancelar = new JButton("Cancelar"), cons);
		
		this.setResizable(false);
		pack();
	}

	public void actionPerformed(ActionEvent event){
		if(event.getSource() == entrar ){
			JOptionPane.showMessageDialog(null,"Yes");
		}else{
			JOptionPane.showMessageDialog(null,"NO");
		}
	}
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		LoginAccess log = new LoginAccess();
		log.show();
	}

}