Form Degrade

import java.awt.Color;
import java.awt.Graphics;
import java.awt.Rectangle;

import javax.swing.JFrame;
import javax.swing.WindowConstants;

/**
 * @author Ademir Constantino Filho <[email removido]>
 */

class DegradeForm extends JFrame {

	public DegradeForm() {
	}

	public void paint(Graphics g) {
		rt = getBounds(null);
		while (alcanca < rt.width) {
			g.setColor(branco);
			g.fillRect(alcanca, 0, alcanca + maximo, rt.height);
			branco = branco.darker();
			alcanca += maximo;
		}
	}

	private Color branco = new Color(255, 255, 255);
	private int maximo = 40;
	private int alcanca = 0;
	private Rectangle rt;
}

public class AplicaDegrade {

	public static void main(String[] argv) {
		DegradeForm meuDegrade = new DegradeForm();
		meuDegrade.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
		meuDegrade.setResizable(false);
		meuDegrade.setSize(400, 200);
		meuDegrade.show();
		meuDegrade.toFront();
	}

}