Competitive/Collaborative Programming Class

/*
 *  Author: Son Pham
 *    Date: January 23, 2013
 * Purpose: Solves this problem using the simplest approach.
 * Problem: 619 - Numerically Speaking
 */

import java.math.BigInteger;
import java.util.Scanner;

public class NumericallySpeaking {

    static String word, number, read;
    static BigInteger[] base = new BigInteger[20];
    
    public static void main(String[] args) {
        
        char type;
        
        for(int i = 0; i < 20; i++){
            base[i] = new BigInteger("26").pow(i);
        }
        
        Scanner reader = new Scanner(System.in);
        read = reader.next();
        while(!(read.equals("*"))){
            if(Character.isDigit(read.charAt(0))){
                type = 'n';
                number = read;
                word = numToWord(number);
            }
            else{
                type = 'w';
                word = read;
                number = wordToNum(word);
            }
            number = insCommas(number);
            word = String.format("%-22s", word);
            System.out.println(word+number);
            read = reader.next();
        }
    }
    
    public static String wordToNum(String s){
        BigInteger calc = new BigInteger("0");
        int length = s.length();
        for (int i = 0, j = length - 1; i < length; ++i, --j){
            int chVal = (int)s.charAt(i) - 96;        
            BigInteger multiple = new BigInteger((""+chVal));
            BigInteger temp = base[j].multiply(multiple);
            calc = calc.add(temp);
        }
        return calc.toString();
    }
    
    public static String numToWord(String s){
        BigInteger value = new BigInteger(s);
        String unmapped = "";
        for(int i = 19; i >= 0; --i){
            if(value.compareTo(base[i]) >= 0){
                BigInteger temp = value.divide(base[i]);
                int chVal = Integer.parseInt(temp.toString());
                char ch = (char)(chVal+96);
                unmapped += ch;
                temp = base[i].multiply(temp);
                value = value.subtract(temp);
            }
        }            
        return unmapped;
    }
    
    public static String insCommas(String s){
        int length = s.length();
        if(length < 4){
            return s;
        }
        else{
            return insCommas(s.substring(0,length-3))+","+s.substring(length-3);
        }
    }
}

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