/* Big Math Factorial  uses Java 1.1 BigInteger class to calculate
   factorial of any int. Calculates distribution of digits in the
   factorial and displays with 50 digits/line formatting. 
                                      M. Gallant    02/14/2000     */

import java.awt.*;
import java.applet.*;
import java.util.*;
import java.math.BigInteger;

public class BigFactorial extends Applet
    {

      public TextArea textArea = new TextArea (15, 60);
      public TextField tf1 = new TextField("30",20 ) ;
      Button factorialn = new Button("Factorial!") ;
      Button clearbutton = new Button("Clear Text") ;

    public void init ()
        {
       factorialn.setBackground(Color.red) ;

            add (clearbutton) ;
            add (tf1) ;
            add (factorialn) ;
            add (textArea);
         }       

   public boolean action(Event evt, Object arg) {     //intercept AWT action.
    if (evt.target == clearbutton) {
     textArea.setText("") ;
     return true ;
     }
    else
      if (evt.target == factorialn) {
               String num = tf1.getText() ;
               String res = getBigFactorial(num) ;
                  if(res.charAt(0) == '!'){
                   textArea.setText(res) ; // bad format returned
                   return true;
                  }
                 textArea.setText("-----------  "+  num+"!  (" + res.length() + " digits)  ------------\n") ;
                 textArea.append(findNumberDistribution(res)+"\n");
                  int index1 = 0;
                  int index2 = 50 ; // display with 50 digits per line
                 while(index2<res.length()) {
                   textArea.append(res.substring(index1,index2) + "\n");
                    index1 += 50 ;
                    index2 += 50 ;
                  }
                 textArea.append(res.substring(index1) + "\n");
           return true;
         }

     else return false;
   }                 // end action handler


    public static String getBigFactorial(String numbstr) { 
     try{
       int numb = Integer.parseInt(numbstr) ;
       BigInteger bnum = new BigInteger(numbstr) ;  // initialize
         for(int j = numb-1; j>1; j--)
           bnum = bnum.multiply(new BigInteger(String.valueOf(j))) ;
        return bnum.toString() ;
       }
     catch (NumberFormatException e) {
       return "!!!Bad number format !!!\n\n" ;
      }
    }

    public String findNumberDistribution(String instring) {
     int checksum=0 ;
     StringBuffer strbuff = new StringBuffer("Digit Count: ") ;
      for(int num=48; num<58; num++){
       int numcount=0;
         for(int i=0; i<instring.length(); i++) {
		if(instring.charAt(i) == num)
		  numcount++ ;
          }
         strbuff.append((char)num + ":" + numcount + "  " ) ;
         checksum += numcount;
      }
      if(checksum != instring.length())
        strbuff.append(" \n ****** digit count is not correct ********* ") ;
      strbuff.append("\n") ;
      return strbuff.toString() ;  // return converted string
    }

  
   public static void main(String args[]) {
    if(args.length!=0)
     try{System.out.println(args[0] + ": \n" + BigFactorial.getBigFactorial(args[0])) ; }
     catch(NumberFormatException nfe) {System.out.println("*** Not an integer ***") ; }
    else
    System.out.println("Command line format:  java BigFactorial integernumber") ;
  }
 
}