Degrade em Componente

package filechooser;

import java.awt.Color;
import java.awt.Dimension;
import java.awt.GradientPaint;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.util.EventListener;

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

public class MyPanel extends JDialog {

	class MultiActionListener implements EventListener {

	}

	private EventListener listener;
	private final Dimension defaultSize = new Dimension(600, 200);

	public MyPanel() {
		this.listener = new MultiActionListener();
		this.setResizable(false);
		this.setSize(this.defaultSize);
		this.getContentPane().setLayout(null);

		JButton br = new JButton("das");
		br.setBounds(10, 10, 100, 30);

		JPanel panel = new JPanel();
		panel.setBackground(Color.BLACK);
		panel.setBounds(10, 50, 100, 30);

		this.getContentPane().add(br);
		this.getContentPane().add(panel);

		this.setVisible(true);
		try {
			Thread.sleep(4000);
		} catch (InterruptedException e) {
			e.printStackTrace();
		}

		System.exit(0);
	}

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

	public void paint(Graphics g) {
		super.paint(g);

		Graphics2D g2d = (Graphics2D) g;
		int height = this.getHeight();
		int width = this.getWidth();

		Color top = new Color(246, 251, 251);
		Color botton = new Color(180, 210, 245);

		// AlphaComposite alpha = //
		// AlphaComposite.getInstance(AlphaComposite.DST_OVER, 1.0f);
		GradientPaint gradient = new GradientPaint(0, 0, top, 0, height, botton); //
		// g2d.setComposite(alpha);
		g2d.setPaint(gradient);

		g2d.fillRect(0, 0, width, height);

	}
}