JavaLine.java

//
// JavaLine.java
// (c) Neil Gershenfeld  2/6/03
// demonstrates Java by animating sin(k*x)/k*x
//

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

public class JavaLine extends JApplet implements Runnable {
   Thread T;
   final int NPTS = 500;
   final int NSTEPS = 100;
   int point,step;
   int x[] = new int[NPTS];
   int y[] = new int[NPTS];
   
   class LinePanel extends JPanel {
      public void paintComponent(Graphics g) {
         super.paintComponent(g);
         super.setBackground(Color.white);
         Graphics2D g2d = (Graphics2D) g;
         GeneralPath path = new GeneralPath(GeneralPath.WIND_EVEN_ODD,NPTS);
         path.moveTo(x[0],y[0]);
         for (point = 1; point < (NPTS-1); ++point) {
            path.lineTo(x[point],y[point]);
         }
         g2d.draw(path);  
      }
   }
   
   public void init() {
      Container C = getContentPane();
      C.add(new LinePanel());
   }
   
   public void start() {
      if (T == null) {
         T = new Thread(this);
         T.start();
      }
   }
   
   public void stop() {
      if (T != null) {
         T = null;
      }
   }
   
   public void run() {
      double r;
      while (true) {
         for (step = 1; step < NSTEPS; ++step) {
            for (point = 0; point < (NPTS-1); ++point) {
               r = 100 * (step*(point+0.5-NPTS/2))/(NPTS*NSTEPS);
               x[point] = point;
               y[point] = (int) ((NPTS/2) - (NPTS/2)*Math.sin(r)/r);
            }
            repaint();
            try {Thread.sleep(10);}
            catch (InterruptedException e) { }
         }
      }
   }
}