Criar evento para um botão de outra classe

import javax.swing.JPanel;
/* * * * * * * * * * * * * * * * * */
import seu.pacote.que.contem.a.sua.classe.Panel;
/* * * * * * * * * * * * * * * * * */
 
 public class PanelAction2 extends JPanel {
 
 	Panel panel = new Panel();
 	
 	
 	public PanelAction2() {
 		super();
 		initialize();
 	}
 
 
 	private void initialize() {
 		/* * * * * * * * * * * * * * * * * */
 		/*Instancie um objeto da SUA classe panel*/
 		Panel seuPanel = new Panel();
 		/* * * * * * * * * * * * * * * * * */
 		this.setSize(300, 200);
 		this.add(panel, null);
 		/* * * * * * * * * * * * * * * * * */
 		JButton btn = seuPanel.getJButton();
 		btn.addActionListener(
 			new AlgumaClasseQueImplementaActionListener()
		);
 		this.add(btn.getJButton());
 		/* * * * * * * * * * * * * * * * * */
 	}
 }

import javax.swing.JPanel;
import javax.swing.JButton;

public class Panel extends JPanel {

	private JButton jButton = null;

	public Panel() {
		super();
		initialize();
	}

	private void initialize() {
		this.setLayout(null);
		this.setSize(60, 60);
		this.add(getJButton(), null);
		this.setVisible(true);
	}

	private JButton getJButton() {
		if (jButton == null) {
			jButton = new JButton();
			jButton.setText("OK");
			jButton.setBounds(new java.awt.Rectangle(0,0,60,60));
		}
		return jButton;
	}
}

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;

public class PanelAction2 extends JFrame {

	Panel panel = new Panel();
	
	
	
	public static void main(String[] args) {
		PanelAction2 action2 = new PanelAction2();
	}
	
	public PanelAction2() {
		super();
		initialize();
	}


	private void initialize() {
		this.setSize(300, 200);
		this.setTitle("teste");
		
		this.add(panel, null);
		this.setVisible(true);
		
		
//		JButton button = new panel.getJButton();
		
	}
}

package botaoEEventoEmClassesDiferentes;

import java.awt.Color;

import javax.swing.BorderFactory;
import javax.swing.JButton;
import javax.swing.JPanel;
import javax.swing.border.TitledBorder;

public class Panel extends JPanel {
	private JButton jButton = null;
	 
 	public Panel() {
 		super();
 		initialize();
 	}
 
 	private void initialize() {
 		this.setLayout(null);
 		this.setBounds(0, 0, 170, 70);
 		this.add(getJButton(), null);
 		this.setVisible(true);
 		setBorder(
 			BorderFactory.createTitledBorder(
 				BorderFactory.createEtchedBorder(
 					Color.BLUE, 
 					Color.GREEN
 				), 
 				"Seu Painel", 
 				TitledBorder.LEFT, 
 				TitledBorder.BOTTOM
 			)
 		);
 		setBackground(Color.WHITE);
 	}
 	
 	/*Eu naum tinha percebido antes, mas se esse método é private daí naum rola.
 	 * Vou deixá-lo protected*/
 	protected JButton getJButton() {
 		if (jButton == null) {
 			jButton = new JButton();
 			jButton.setText("OK");
 			jButton.setBounds(new java.awt.Rectangle(0,0,60,60));
 		}
 		return jButton;
 	}

}

package botaoEEventoEmClassesDiferentes;

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

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

public class PanelAction2 extends JFrame {
	private class Handler implements ActionListener {

		public void actionPerformed(ActionEvent e) {
			JOptionPane.showMessageDialog(
				((Component)e.getSource()).getParent(), 
				"Testando evento do Botão"
			);
		}

	}


	Panel panel = new Panel();
 	
 	public static void main(String[] args) {
 		PanelAction2 action2 = new PanelAction2();
 		action2.show();
 	}
 	
 	public PanelAction2() {
 		super();
 		initialize();
 	}
 
 
 	private void initialize() {
 		setSize(300, 200);
 		setTitle("teste");
 		getContentPane().setLayout(null);
 		
 		JButton button = panel.getJButton();
 		button.addActionListener(new Handler());
 		button.setBounds(0, 130, 70, 30);
 		
 		getContentPane().add(button);
 		getContentPane().add(panel);
 		
 	}
 }