import javax.swing.*;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.geom.*;
import java.awt.Color;
import java.awt.GradientPaint;

public class PaintTest3 extends JPanel{

  public static void main(String[] args){
    JFrame frame = new JFrame();

    PaintTest3 app = new PaintTest3();
    frame.getContentPane().add(app);

    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setBounds(10, 10, 300, 200);
    frame.setTitle("ƒ^ƒCƒgƒ‹");
    frame.setVisible(true);
  }

  public void paintComponent(Graphics g){
    Graphics2D g2 = (Graphics2D)g;

    g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, 
                        RenderingHints.VALUE_ANTIALIAS_ON);

    GradientPaint gradient = new GradientPaint(
        90.0f, 70.0f, Color.RED, 
        150.0f, 90.0f, Color.BLUE,
        true
    );
    g2.setPaint(gradient);

    g2.fill(new Rectangle2D.Double(20, 20, 200, 130));

/*
    g2.setPaint(Color.black);
    g2.draw(new Ellipse2D.Double(85, 65, 10, 10));
    g2.draw(new Ellipse2D.Double(145, 85, 10, 10));
*/
  }
}