Convert a number/Currency to its expression in words

Number To word Converter

Lets consider one scenario where user enters currency in currency/Number format and system need to convert that Currency/number to word format.

ex: $2345.12
Output: USD Two Thousand Three Hundreed Fourty Five and twelve cent.

Create a class NumberToWord 

public  class NumberToWord { 
    static String[] to_19 = new string[]{ 'zero', 'one',  'two', 'three', 'four',  'five', 

 'six', 'seven', 'eight', 'nine', 'ten',  'eleven', 'twelve', 'thirteen', 
     'fourteen', 'fifteen', 'sixteen', 'seventeen', 'eighteen', 'nineteen' }; 
    static String[] tens = new string[]{ 'twenty', 'thirty', 'forty', 'fifty', 'sixty', 

                               'seventy', 'eighty', 'ninety'}; 

    static String[] denom = new string[]{ '', 
     'thousand',   'million',     'billion',    'trillion',    'quadrillion', 
    'quintillion', 's!xtillion',   'septillion',  'octillion',   'nonillion', 
      'decillion',  'undecillion',   'duodecillion', 'tredecillion',  'quattuordecillion', 
      's!xdecillion', 'septendecillion', 'octodecillion', 'novemdecillion', 'vigintillion' }; 
    // convert a value < 100 to English.   
   public static String convert_nn(integer val) { 
      if (val < 20) 
        return to_19[val]; 
     if(val == 100) 
          return 'One Hundred'; 
      for (integer v = 0; v < tens.size(); v++) { 
        String dcap = tens[v]; 
        integer dval = 20 + 10 * v; 
        if (dval + 10 > val) { 
          if (Math.Mod(val,10) != 0) 
            return dcap + ' ' + to_19[Math.Mod(val,10)]; 
          return dcap; 
        }     
      } 
      return 'Should never get here, less than 100 failure'; 
    } 
    // convert a value < 1000 to english, special cased because it is the level that kicks  
    // off the < 100 special case. The rest are more general. This also allows you to 
    // get strings in the form of "forty-five hundred" if called directly. 
    public static String convert_nnn(integer val) { 
      String word = ''; 
      integer rem = val / 100; 
      integer mod = Math.mod(val,100); 
      if (rem > 0) { 
        word = to_19[rem] + ' hundred'; 
        if (mod > 0) { 
          word += ' '; 
        } 
      } 
      if (mod > 0) { 
        word += convert_nn(mod); 
      } 
      return word; 
    } 
    public static String english_number(long val) { 
      if (val < 100) { 
        return convert_nn(val.intValue()); 
      } 
      if (val < 1000) { 
        return convert_nnn(val.intValue()); 
      } 
      for (integer v = 0; v < denom.size(); v++) { 
        integer didx = v - 1; 
        integer dval = (integer)Math.pow(1000, v); 
        if (dval > val) { 
          integer mod = (integer)Math.pow(1000, didx); 
          integer l = (integer) val / mod; 
          integer r = (integer) val - (l * mod); 
          String ret = convert_nnn(l) + ' ' + denom[didx]; 
          if (r > 0) { 
           ret += ', ' + english_number(r); 
          } 
          return ret; 
        } 
     } 
     return 'Should never get here, bottomed out in english_number'; 
   } 
 }

This method not handles for decimal point, so we need to call this class methods twice (once with passing number prior to the decimal point and another one with after decimal point)to convert the currency to word with decimal part .

lets consider I have a currency field test_currency__c in test_ob__c object and i have entered 5678.43 as value for this field.
I want to convert this field value to word format as USD five thousand six hundred seventy eight and fourtyThree cents.

string enteredCurrency = string.valueof(testObj.test_currency__c );
integer decimalIndex= enteredCurrency.indexOf('.');
integer part1=integer.valueof(enteredCurrency.substring(0,decimalIndex));
integer part2=integer.valueof(enteredCurrency.substring(decimalIndex+1));
//Now call the method to convert to word format for number prior to the decimal point
string currencyPart1InWord =  NumberToWord.english_number(part1);
string currencyPart2InWord='';
string amountInWords;
if(part2>0){
       currencyPart2InWord=NumberToWord.english_number(part2);
}
string amountInWords='USD '+currencyPart1InWord;
if(currencyPart2InWord!=null && currencyPart2InWord!=''){
        amountInWords=amountInWords+' and '+ currencyPart2InWord +' cents';
}
amountInWords=amountInWords+' only*';

Now you can get output as USD five thousand six hundred seventy eight and fourtyThree cents.