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

// A simple model with one piece of data, setters & getters, and an action method
public class Model 
{
  private int x=15; // the model data
  private View view; // the model's view

  public Model()
  {
    view = new View(this);  // create a view passing itself as the model
  }

  public int position() {return x;} // access for View
  public void hop() {x+=20; } // change model data

  // change model data over some time
  public void action() 
  {
    // let the ball move a number of times
    for (int i=5; i<200; i+=20)
    {
      hop(); // make a change to the model
      view.repaint();  // ask view to refresh itself 

      // wait a bit in so that intermediate steps can be seen
      // otherwise repaint collects all updates
      for (int j=0; j<250000; j++)
        Math.pow(2, 64);
    }
  }

  public static void main(String args[])
  {
    Model model=new Model();  // create a new model (creates its own view)
    
    // wait a bit for view to be fully displayed
    for (int j=0; j<500000; j++)
      Math.pow(2, 64);

    model.action();  // change model data over some time
  }
}

class View extends JFrame {

  public View(Model model)
  {
    super("Swing Example"); // set window title
    setSize(300, 170); // set window size

    // make window react to close box event
    addWindowListener(
      new WindowAdapter() {
        public void windowClosing(WindowEvent e) {
          System.exit(0);
        }
      }
    );
      
    // replace content pane with new playfield component
    setContentPane(new PlayfieldPanel(model));
    
    // show window
    setVisible(true);  
  }
}


// A new Swing component responsible for showing the playing field
// inherits from JPanel to obtain background & double buffering
class PlayfieldPanel extends JPanel 
{ 
  private Model model;  // the model to be visualized

  public PlayfieldPanel(Model m)  // accepts model from view
  {
    model=m;  // save model for later access
    setBackground(Color.green.darker());  // grass is green...      
  }

  // this is called whenever the playfiled is redrawn (e.g., on repaint)
  public void paintComponent(Graphics g)  
  {
    super.paintComponent(g);  // draw (green) background first

    g.setColor(Color.white);  // set white foreground color
    g.fillOval(model.position(), 50, 35, 35); // draw ball at a position obtained from model
  }
}