// Suprise.java
// Fills a window with a big yellow circle

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

public class Surprise
{
  int diameter = 0;
  static int SIZE = 800; 
  int panelHeight, panelWidth; 


   public static void main(String args [])
   {
      Surprise s = new Surprise();
      s.go();
   }

  public void go()
  {
      JFrame window = new JFrame("Surprise!");
      SurprisePanel sp = new SurprisePanel();
      sp.setBackground(Color.BLUE);
      window.setSize (SIZE, SIZE);
      window.add (sp);
      window.setVisible(true);
      window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

      panelHeight = sp.getSize().height;
      panelWidth = sp.getSize().width;
      while (diameter < Math.min(panelHeight, panelWidth))
      {
         diameter++;
         try {Thread.sleep(15); }               // sleep for 15 msec
         catch (InterruptedException e) { };
         sp.repaint();
      }
      Graphics g = sp.getGraphics();
      g.setColor(Color.RED);
      g.setFont(new Font("Courier", Font.BOLD, 36));
      FontMetrics metrics = g.getFontMetrics();
      try {Thread.sleep(1000); }               // pause for 1 sec
      catch (InterruptedException e) { };
      g.drawString("Surprise!", (panelWidth-metrics.stringWidth("Surprise"))/2,
                    (panelHeight+metrics.getHeight())/2);

   }

  class SurprisePanel extends JPanel 
  {   // an inner class so we can use the diameter, 
      // panelHeight, and panelWidth variables

     public void paintComponent (Graphics g)
     {
        super.paintComponent(g);
        g.setColor(Color.YELLOW);
        g.fillOval((panelWidth-diameter)/2, (panelHeight-diameter)/2,
                     diameter, diameter);
     }
  }
}