Java Swing - 如何扩展JLabel以创建渐变标签

/*
 *  soapUI, copyright (C) 2004-2009 eviware.com 
 *
 *  soapUI is free software; you can redistribute it and/or modify it under the 
 *  terms of version 2.1 of the GNU Lesser General Public License as published by 
 *  the Free Software Foundation.
 *
 *  soapUI is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without 
 *  even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. 
 *  See the GNU Lesser General Public License for more details at gnu.org.
 */

import java.awt.Color;
import java.awt.GradientPaint;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Paint;

import javax.swing.JLabel;
import javax.swing.JOptionPane;

public class Main {
  public static void main(String[] args) throws Exception {
    GradientLabel label = new GradientLabel("w3cschool.cn");

    JOptionPane.showMessageDialog(null, label);

  }
}

class GradientLabel extends JLabel {
  // ------------------------------ FIELDS ------------------------------

  private Color start;
  private Color end;

  // --------------------------- CONSTRUCTORS ---------------------------

  public GradientLabel(String text) {
    super(text);

    start = Color.LIGHT_GRAY;
    end = getBackground();
  }

  public GradientLabel(String text, Color start, Color end) {
    super(text);
    this.start = start;
    this.end = end;
  }

  // -------------------------- OTHER METHODS --------------------------

  public void paint(Graphics g) {
    int width = getWidth();
    int height = getHeight();

    // Create the gradient paint
    GradientPaint paint = new GradientPaint(0, 0, start, width, height, end,
        true);

    // we need to cast to Graphics2D for this operation
    Graphics2D g2d = (Graphics2D) g;

    // save the old paint
    Paint oldPaint = g2d.getPaint();

    // set the paint to use for this operation
    g2d.setPaint(paint);

    // fill the background using the paint
    g2d.fillRect(0, 0, width, height);

    // restore the original paint
    g2d.setPaint(oldPaint);

    super.paint(g);
  }
}