import java.awt.*;import java.applet.*;import java.net.URL;import java.util.*;import graph.*;/*****************************************************************************    Applet example2a**                                              Version 1.0   August 1996******************************************************************************    Copyright (C) 1996 Leigh Brookshaw****    This program is free software; you can redistribute it and/or modify**    it under the terms of the GNU General Public License as published by**    the Free Software Foundation; either version 2 of the License, or**    (at your option) any later version.****    This program is distributed in the hope that it will be useful,**    but WITHOUT ANY WARRANTY; without even the implied warranty of**    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the**    GNU General Public License for more details.****    You should have received a copy of the GNU General Public License**    along with this program; if not, write to the Free Software**    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.******************************************************************************    This is a simple applet that creates a Scroll Chart using the **    Graph2D class library and double buffering***************************************************************************/public class example2a extends Applet implements Runnable {      Graph2D graph;      Label title;      DataSet data1 = new DataSet();      Axis    yaxis_right;      Image    osi = null;      Graphics osg = null;      int iwidth  = 0;      int iheight = 0;      Thread runner = null;      Random random = new Random();      int count = 0;/***    In milliseconds how often do we want to add a new data point.*/      int period      = 500;/***    Maximum number of points to display before scrolling the data*/      int maximum        = 25;      URL markersURL;/***    Initialize the applet. The Parameters passed are the title of the plot**    the marker file to use and the update period in milliseconds*/      public void init() {        int i;        int j;/***      Get the passed parameters*/        String st       = getParameter("TITLE");        String mfile    = getParameter("MARKERS");        try {             period   = Integer.parseInt(getParameter("PERIOD"));	   }        catch (Exception e) {             System.out.println("Frequency parameter not an Integer!");	}/***      Create the Graph instance and modify the default behaviour*/        graph = new Graph2D();        graph.zerocolor = new Color(0,255,0);        graph.borderTop    = 50;        graph.borderBottom = 50;        graph.setDataBackground(Color.black);/***      Create the Title*/        title = new Label(st, Label.CENTER);        title.setFont(new Font("TimesRoman",Font.PLAIN,25));        setLayout( new BorderLayout() );        add("North",  title);        add("Center", graph);/***      Load a file containing Marker definitions*/        try {           markersURL = new URL(getDocumentBase(),mfile);           graph.setMarkers(new Markers(markersURL));        } catch(Exception e) {           System.out.println("Failed to create Marker URL!");        } /***      Modify the default Data behaviour*/        data1.linecolor   = new Color(255,0,0);        data1.marker      = 1;        data1.markercolor = new Color(100,100,255);/***      Setup the Axis. Attach it to the Graph2D instance, and attach the data**      to it.*/        yaxis_right = graph.createAxis(Axis.RIGHT);        yaxis_right.attachDataSet(data1);        yaxis_right.setLabelFont(new Font("Helvetica",Font.PLAIN,20));        graph.attachDataSet(data1);      }      public void start() {	if(runner == null) {          runner = new Thread(this);          runner.start();        }      }      public void stop() {	if(runner != null) {          runner.stop();          runner = null;        }      }        public void run() {              int i =0;              double data[] = new double[2];              Graphics g;              while(true) {                   count++;                   if(count >= maximum) data1.delete(0,0);                   data[1] = (2.0*random.nextDouble()-1.0)*50.0;                   data[0] = count;                   try {                        data1.append(data,1);		      }                   catch (Exception e) {                        System.out.println("Error appending Data!");                   }                   data1.yaxis.maximum =  50.0;                   data1.yaxis.minimum = -50.0;                                      g = graph.getGraphics();		   if( osi == null || iwidth != graph.size().width                                   || iheight != graph.size().height  ) {                       iwidth = graph.size().width;                       iheight = graph.size().height;                       osi = graph.createImage(iwidth,iheight);                       osg = osi.getGraphics();                   }                   osg.setColor(this.getBackground());                   osg.fillRect(0,0,iwidth,iheight);                   osg.setColor(g.getColor());                   osg.clipRect(0,0,iwidth,iheight);                   graph.update(osg);                   g.drawImage(osi,0,0,graph);                   try {  Thread.sleep(period); }                   catch(Exception e) { }	     }	}}