Java AWT Graphics2D set gradient paint

import java.awt.Color;
import java.awt.GradientPaint;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.geom.RoundRectangle2D;
import java.util.Random;

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

public class Main extends JPanel {
  Random rnd = new Random();
  @Override/* w ww  .  j  a va 2s  .co  m*/
  public void paintComponent(Graphics g) {
    super.paintComponent(g);
    
    Graphics2D g2d = (Graphics2D) g;
    g2d.setBackground(Color.WHITE);
    g2d.clearRect(0, 0, getParent().getWidth(), getParent().getHeight());
    // antialising
    g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);

    //RoundRectangle2D
    RoundRectangle2D roundRect = new RoundRectangle2D.Float(50, 50, 100, 70, 20, 20);
    GradientPaint gradient3 = new GradientPaint(50, 50, Color.GREEN, 70,70, Color.BLACK, true);
    g2d.setPaint(gradient3);
    g2d.fill(roundRect); 
    
  }

  public static void main(String[] args) {
    // create frame for Main
    JFrame frame = new JFrame("java2s.com");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    Main Main = new Main();
    frame.add(Main);
    frame.setSize(300, 210);
    frame.setVisible(true);
  }
}