Untitled

package Labs.Assignment6;
import java.util.*;
public class QuestionSixPointThrityOne {
  public static int sumOfOddPlace(ArrayList<Integer> cardNumberList)
  {
    /*
     * 1. Take in the arrayList that contains the digits of the card number 
     * and iterate through it
     * 2. sum up all the odd place digits 
     * 3. start at 15 and subtract two until count is less than 0 than break
     * 4. return the sum
     */
    int sum = 0;
    int count =cardNumberList.size()-1;
    for(int i = 0; i< (cardNumberList.size());i++)
    {
      int product = cardNumberList.get(count);
      sum = sum + product;
      count-=2;
      if(count <0)
      {
        break;
      }
    }
    return sum;
  }

  public static ArrayList<Integer> cardNumList(long cardNumber)
  {
    /*
     * 1.Take in the long number and convert it to a string
     * 2. convert the string into an array of characters
     * 3. iterate through the array and convert every value into and integer than add it to an
     * array list
     * 4.return the arraylist
     */
    ArrayList<Integer> cardNumberList = new ArrayList<>();
    String cardNumberString = Long.toString(cardNumber);
    char[] digits = cardNumberString.toCharArray();
    for(int i = 0; i<(digits.length); i++)
    {
      int num = Character.getNumericValue(digits[i]);
      cardNumberList.add(num);
    }
    return cardNumberList;
  }

  public static int sumFunctionForTwoPlaces(int product)
{
  /*
   * 1.take
   */
  int remainder =0;
  int sum = 0;
  while(product > 0)
    {
        remainder =product%10;
        sum += remainder;
        product = product / 10;
    }
  return sum;
}

public static int sumOfEvenPlace(ArrayList<Integer> cardNumberList)
{/*
   * 1.take in the arrayList of the digits of the card
   * 2.iterate throught the arrayList starting at 14 and change the index by 2 every time
   * 3.multiply the digit by 2 then check the length if it 
   * 4.if the lenght of the product  is greater than 1, 
   * then send it to the sumFunctionForTwoPlaces method and add the return value to the sum
   * 5.if it is equal to 1 add the product to the sum 
   * 6.check if the count is less than zeor if it is break if not continue
   * 7.return the sum value
   */
  int sum =0;
  int count =cardNumberList.size()-2;
  for(int i = 0; i< (cardNumberList.size());i++)
  {
    int product = cardNumberList.get(count) * 2;
    int length = Integer.toString(product).length();
    if(length>1)
    {
      int sumOfProduct = sumFunctionForTwoPlaces(product);
      sum = sum + sumOfProduct;
    }
    if(length ==1)
    {
      sum = sum + product;
    }
    count-=2;
    if(count <0)
    {
      break;
    }
  }
  return sum;
}
  
  public static void main(String[] args)
  {
    Scanner scanner = new Scanner(System.in);
    int stepOneSum;
    int stepTwoSum;
    System.out.println("Enter a credit card number as a long integer:");
    long cardNumber = scanner.nextLong();
    ArrayList<Integer> cardNumberList = cardNumList(cardNumber);
    stepOneSum = sumOfEvenPlace(cardNumberList);
    stepTwoSum =  sumOfOddPlace(cardNumberList);
    int finalSum = stepOneSum + stepTwoSum;
    if(finalSum%10 == 0)
    {
      System.out.printf("%d is valid",cardNumber);
    }

    if(finalSum%10 != 0)
    {
      System.out.printf("%d is invalid",cardNumber);
    }
    
    scanner.close();
  }
    
}