Java 1.2 How-To/JavaHowTo.iso/javafile/ch03/ChartApp.java

Java Source | 1998-12-14 | 4.9 KB | 223 lines

import java.applet.Applet;
import java.awt.*;

/**
 * parent class
 */
class Chart {

/*
 * x and y positions of the upper-left of the chart
 * nvalues - number of values for this chart
 */
int xpos, ypos, nvalues;

/*
 * width and height of this chart
 */
int width, height;

/*
 * maximum number of values allowed
 */
final int MaxValues = 10;

/*
 * data values for this chart
 */
double values[] = new double[MaxValues];

/*
 * color associated with each value
 */
Color colors[] = new Color[MaxValues];

/*
 * sum total of values, used for scaling purposes
 */
double total;

/**
 * class constructor
 * save values and normalizes them so that the max. value is 1.0
 * @param x, y - top-left coordinates
 * @param w, h - width and height
 * @param n - number of points
 * @param val[] - array of values
 * @param c[] - array of colors corresponding to values
 */
public Chart (int x, int y, int w, int h, int n, double val[], Color c[]) {

      int i;
      double extreme;

      xpos = x;
      ypos = y;
      width = w;
      height = h;
      nvalues = n;
      if (nvalues > MaxValues) nvalues = MaxValues;
      extreme = 0.0;
      for (i=0; i<nvalues; i+=1) {
            if (Math.abs (val[i]) > extreme)
                  extreme = Math.abs (val[i]);
            colors[i] = c[i];
      }
      extreme = 1/extreme;
      total = 0;
      for (i=0; i<nvalues; i+=1) {
            values[i] = extreme * val[i];
            total += values[i];
      }
}
}

/**
 * class implements a bar chart
 */
class BarChart extends Chart {

/**
 * constructor just calls Chart constructor
 * @param x, y - top left coordinates
 * @param w, h - width and height
 * @param n - number of points
 * @param val[] - array of values
 * @param c[] - array of colors corresponding to values
 */
public BarChart (int x, int y, int w, int h, int n, double val[], Color c[]) {

      super (x, y, w, h, n, val, c);
}

/**
 * need to add a paint method
 * draws the bar chart using fill3DRect
 * @param g - destination graphics object
 */
void paint (Graphics g) {

      int i;
      int barwidth = 3 * width / (4 * nvalues);
      int bardx = width / nvalues;
      int x, y, h;

      g.setColor (Color.black);
      g.fillRect (xpos, ypos-height, width, height);
      for (i=0; i<nvalues; i+=1) {
            g.setColor (colors[i]);
            x = xpos + bardx*i;
            h = (int) (values[i] * height);
            y = ypos - h;
            g.fill3DRect (x, y, barwidth, h, true);
      }
}
}

/**
 * class implements a pie chart
 */
class PieChart extends Chart {

/**
 * class constructor just calls Chart constructor
 * @param x, y - top-left coordinates
 * @param w, h - width and height
 * @param n - number of points
 * @param val[] - array of values
 * @param c[] - array of colors corresponding to values
 */
public PieChart (int x, int y, int w, int h, int n, double val[], Color c[]) {

      super (x, y, w, h, n, val, c);
}

/**
 * need to add a paint method
 * draws the pie chart using fillArc
 * @param g - destination graphics object
 */
void paint (Graphics g) {

      int i, y;
      int startAngle, arcAngle;

      startAngle = 0;
      y = ypos - height;
      for (i=0; i<nvalues; i+=1) {
            arcAngle = (int) (360.0 * values[i] / total);
            g.setColor (colors[i]);
            g.fillArc (xpos, y, width, height, startAngle, arcAngle);
startAngle += arcAngle;
      }
}
}

/**
 * the applet/application  proper
 */
public class ChartApp extends Applet {

/*
 * width and height of the bounding panel
 */
int width, height;

/*
 * instances of BarChart and PieChart
 */
BarChart bc1;
PieChart pc1;

/*
 * called when applet is loaded
 * generate random values and plot them
 */
public void init () {

      int i;
      double values[] = new double[5];
      Color colors[] = new Color[5];

      width = 410;
      height = 230;
      colors[0] = Color.blue;
      colors[1] = Color.orange;
      colors[2] = Color.yellow;
      colors[3] = Color.green;
      colors[4] = Color.magenta;

      for (i=0; i<5; i+=1) values[i] = Math.random () + 0.001;
      int w = (width-40)/2;
      int h = height-20;
      bc1 = new BarChart (10, height-10, w, h, 5, values, colors);
pc1 = new PieChart (width/2, height-10, w, h, 5, values, colors);
}

/**
 * invoke the chart paint methods
 * @param g - destination graphics object
 */
public void paint (Graphics g) {

      bc1.paint (g);
      pc1.paint (g);
}

/**
 * application entry point
 * create a window frame and add the applet inside
 * @param args[] - command-line arguments
 */
public static void main (String args[]) {

      Frame f = new Frame ("Charts");
      ChartApp chart = new ChartApp ();

      f.setSize (410, 230);
      f.add ("Center", chart);
      f.show ();
      chart.init ();
      chart.start ();
}
}