================file:  Dist.java============================
/*  class Dist generic distribution function.
 <applet code=G3.class width=300 height=400>
        alt="Your browser understands the &lt;APPLET&gt; tag but isn't running the applet, for some reason."
        Your browser is completely ignoring the &lt;APPLET&gt; tag!
      </applet>

 */


public class Dist {

public static double hw=1.0;// measure energy in hw.
public static double kt=25.0;// temperature
public static  double n = 20000; //number of atoms
double clow = 2.;
double chigh = 2.;
double c = 2.;

int max_e =0;
int max_n =0;


    
    void findc(){
    c=2;
    while(sum()>n){c*=2;}
    chigh=c;
    while(sum()<n){c/=2;}
    clow=c;
    c=(chigh+clow)/2.0;
     while(Math.abs((sum()-n))>0.0001*n){
     if(sum()>n) clow=c; else chigh=c;
     c=(chigh+clow)/2.0;
     }
    }


    double f(int i) {
    return g(i)/(c*Math.exp(hw*i/kt)-1.);
    }



double sum(){
  int summ=300;//include 300 terms
  double sum;

  double maxn=0.0;
  sum=0.0;
  for(int i=0;i<summ;i++){
    double fv=f(i);
    if(fv>maxn){
      maxn=fv;
      max_n=(int)(fv+.5);
      max_e=i;
    }
    sum = sum+fv;
  }
  return sum;
}

static double g(int i){
  return (i+2.)*(i+1.)/2.;
}

}
================file:  FDDist.java============================
/*  class Dist generic distribution function.
 <applet code=G3.class width=300 height=400>
        alt="Your browser understands the &lt;APPLET&gt; tag but isn't running the applet, for some reason."
        Your browser is completely ignoring the &lt;APPLET&gt; tag!
      </applet>

 */


public class FDDist extends Dist {


    


    double f(int i) {
    return g(i)/(c*Math.exp(hw*i/kt)+1.0);
    }



}

================file:  G3.java============================
/* graph BEdist
 <applet code=G3.class width=600 height=800>
        alt="Your browser understands the &lt;APPLET&gt; tag but isn't running the applet, for some reason."
        Your browser is completely ignoring the &lt;APPLET&gt; tag!
      </applet>

 */

import java.awt.Graphics;
import java.awt.*;

public class G3 extends java.applet.Applet {


int scrollint=0;
int scrollintold=0;
G3 myapp = this;
Timer1 timer= new Timer1(this);

Dist be = new Dist();
MBDist mb = new MBDist();
FDDist fd = new FDDist();
Scrollbar s = new Scrollbar(Scrollbar.HORIZONTAL,250,10,1,500);

    public void init() {
    Choice c;
    setLayout(new BorderLayout() );
    Panel p = new Panel();
    p.setLayout(new BorderLayout() );
    p.add("North",s);
    Panel p1 = new Panel();
    p1.add(new Label("M ="));
    p1.add(c=new Choice());
    c.addItem("10000");
    c.addItem("5000");
    c.addItem("1000");
    c.addItem("500");
    c.addItem("100");
    c.addItem("50");
    c.addItem("10");
    p.add("South",p1);
    add("North",p);
    timer.start();
  }

  public boolean action(Event evt,Object arg){
       if (evt.target instanceof Choice) {
       be.n = Integer.parseInt(arg.toString());
       myapp.repaint();
       }
    return true;
  }

  public void step() {
   scrollintold=scrollint;
   scrollint=s.getValue();
   if(scrollint != scrollintold) {
    be.kt=scrollint/10.0;
    repaint();
    }
}



    



    public void paint(Graphics g) {
      be.findc();
      mb.findc();
      mb.sum();
      fd.findc();

        int left=10;
        int right=size().width-10;
        int top=40;
        int bottom=size().height-10;
        int b2=(bottom-top)*2/3+top;
        int b3=(bottom-top)/3+top;

        System.out.println("painting with kt "+be.kt);
        g.setColor(Color.red);
        g.drawString("Bose-Einstein",right-150,top+30);
        g.drawString("kT = "+be.kt,right-150,top+40);
        g.drawString("Emax, N = "+be.max_e+", "+be.max_n,right-150,top+50);
        g.setColor(Color.blue);
        g.drawString("Maxwell Boltzman",right-150,b3+30);
        g.drawString("kT = "+mb.kt,right-150,b3+40);
        g.drawString("Emax, N = "+mb.max_e+", "+mb.max_n,right-150,b3+50);
        g.setColor(Color.black);
        g.drawString("Fermi Dirac",right-150,b2+30);
        g.drawString("kT = "+fd.kt,right-150,b2+40);
        g.drawString("Emax, N = "+fd.max_e+", "+fd.max_n,right-150,b2+50);

        for (int x =left ; x < 300+left ; x++) {
          g.setColor(Color.red);
	  g.drawLine(2*x,b3,2*x, b3-(int)(be.f(x-left)+.5));
	  g.drawLine(2*x,b3-(int)(be.f(x-left)+.5),2*x+1, b3-(int)(be.f(x-left)+.5));
          g.setColor(Color.blue);
	  g.drawLine(2*x,b2,2*x, b2-(int)(mb.f(x-left)+.5));
	  g.drawLine(2*x,b2-(int)(mb.f(x-left)+.5),2*x+1, b2-(int)(mb.f(x-left)+.5));
          g.setColor(Color.black);
	  g.drawLine(2*x,bottom,2*x, bottom-(int)(fd.f(x-left)+.5));
	  g.drawLine(2*x,bottom-(int)(fd.f(x-left)+.5),2*x+1, bottom-(int)(fd.f(x-left)+.5));
        }
    }
  public String getAppletInfo() {
    return "Draws a Distribution graph.";
  }


}


class Timer1 extends Thread {
  G3 myapplet;

  public Timer1(G3 myapplet){
    this.myapplet=myapplet ;
    setPriority(MIN_PRIORITY);
    }
   public void run() {
   for(;;){
     myapplet.step();
     yield();
     try{sleep(1000L);} catch(InterruptedException e){;}
     }
   }
}

================file:  MBDist.java============================
/*  class Dist generic distribution function.
 <applet code=G3.class width=300 height=400>
        alt="Your browser understands the &lt;APPLET&gt; tag but isn't running the applet, for some reason."
        Your browser is completely ignoring the &lt;APPLET&gt; tag!
      </applet>

 */


public class MBDist extends Dist {


    
    void findc(){
    c=1.0;
    c=sum()/n;
    }


    double f(int i) {
    return g(i)/(c*Math.exp(hw*i/kt));
    }



}