public class CreditCardValidation
{
   public static void main(String [] args)
   {
     int creditCardNum [] = {4,3,1,2,6,5,7,8,4,3,2,1,9,6,7,3};
	 boolean answer = true;
	 answer = luhnFormula(creditCardNum);
	 if (answer == true)
	    System.out.print("Valid Credit Card");
	else
		System.out.print("Invalid Credit Card");
   }

   public static boolean luhnFormula(int ccn [])
   {
	 int oddSum = 0, evenSum = 0, overallSum = 0;
	 boolean valid = true;
	 oddSum = addNumbersInOdd(ccn);
	 evenSum = addNumbersInEven(ccn);
	 overallSum = oddSum + evenSum;
	 if(overallSum % 10 != 0)
		 valid = false;
	 else
		 valid = true;
	 return valid;
   }

   public static int addNumbersInOdd(int [] n)
   {
	   int oddSum = 0, d;
	   for(int i = 0; i < n.length ; i += 2)
	   {
		   d = n[i];
		   d = d * 2;
		   if(d > 10)
		   {
			   d = d % 10 + 1;
		   }
		   oddSum += d;

	   }
	   return oddSum;
   }

   public static int addNumbersInEven(int [] m)
   {
	   int evenSum = 0;
	   for(int i = 1; i < m.length ; i += 2)
	   {
		   evenSum += m[i] ;
	   }
	   return evenSum;
   }
}