Java Luhn algorithm Card Number Generator
Tags: java, luhn, algorithms, card
Published: 2020-02-18 03:43:45


       import java.util.List;
       import java.util.Stack;
       import java.util.Vector;

       public class RandomCardNumberGenerator {
	
	
	public static final String[] MASTERCARD_PREFIX_LIST = new String[] { "0626" };
	
	
	public static final String[] VISA_PREFIX_LIST = new String[] { "4539",
			"4556", "4916", "4532", "4929", "40240071", "4485", "4716", "4" };
	
	public static final String[] MASTERCARD_PREFIX_LIST2 = new String[] { "51",
			"52", "53", "54", "55" };

	public static final String[] AMEX_PREFIX_LIST = new String[] { "34", "37" };

	public static final String[] DISCOVER_PREFIX_LIST = new String[] { "6011" };

	public static final String[] DINERS_PREFIX_LIST = new String[] { "300",
			"301", "302", "303", "36", "38" };

	public static final String[] ENROUTE_PREFIX_LIST = new String[] { "2014",
			"2149" };

	public static final String[] JCB_PREFIX_LIST = new String[] { "35" };

	public static final String[] VOYAGER_PREFIX_LIST = new String[] { "8699" };
	

	static String strrev(String str) {
		if (str == null)
			return "";
		String revstr = "";
		for (int i = str.length() - 1; i >= 0; i--) {
			revstr += str.charAt(i);
		}

		return revstr;
	}

	static String completed_number(String prefix, int length) 
	{

		String ccnumber = prefix;

		while (ccnumber.length() < (length - 1)) {
			ccnumber += new Double(Math.floor(Math.random() * 10)).intValue();
		}

		String reversedCCnumberString = strrev(ccnumber);

		List<Integer> reversedCCnumberList = new Vector<Integer>();
		for (int i = 0; i < reversedCCnumberString.length(); i++) {
			reversedCCnumberList.add(new Integer(String
					.valueOf(reversedCCnumberString.charAt(i))));
		}

		int sum = 0;
		int pos = 0;

		Integer[] reversedCCnumber = reversedCCnumberList
				.toArray(new Integer[reversedCCnumberList.size()]);
		while (pos < length - 1) {

			int odd = reversedCCnumber[pos] * 2;
			if (odd > 9) {
				odd -= 9;
			}

			sum += odd;

			if (pos != (length - 2)) {
				sum += reversedCCnumber[pos + 1];
			}
			pos += 2;
		}

		int checkdigit = new Double(
				((Math.floor(sum / 10) + 1) * 10 - sum) % 10).intValue();
		ccnumber += checkdigit;

		return ccnumber;

	}

	public static String[] credit_card_number(String[] prefixList, int length,int howMany) 
	{

		Stack<String> result = new Stack<String>();
		for (int i = 0; i < howMany; i++) {
			int randomArrayIndex = (int) Math.floor(Math.random()
					* prefixList.length);
			String ccnumber = prefixList[randomArrayIndex];
			result.push(completed_number(ccnumber, length));
		}

		return result.toArray(new String[result.size()]);
	}

	public static String[] generateMasterCardNumbers(int howMany) {
		return credit_card_number(MASTERCARD_PREFIX_LIST, 16, howMany);
	}

	public static String generateMasterCardNumber() {
		return credit_card_number(MASTERCARD_PREFIX_LIST, 16, 1)[0];
	}

	public static boolean isValidCreditCardNumber(String creditCardNumber) {
		boolean isValid = false;

		try {
			String reversedNumber = new StringBuffer(creditCardNumber)
					.reverse().toString();
			int mod10Count = 0;
			for (int i = 0; i < reversedNumber.length(); i++) {
				int augend = Integer.parseInt(String.valueOf(reversedNumber
						.charAt(i)));
				if (((i + 1) % 2) == 0) {
					String productString = String.valueOf(augend * 2);
					augend = 0;
					for (int j = 0; j < productString.length(); j++) {
						augend += Integer.parseInt(String.valueOf(productString
								.charAt(j)));
					}
				}

				mod10Count += augend;
			}

			if ((mod10Count % 10) == 0) {
				isValid = true;
			}
		} catch (NumberFormatException e) {
		}

		return isValid;
	}
	
	private static int sumToSingleDigit(int k)
	{
		if (k < 10)
		return k;
		return sumToSingleDigit(k / 10) + (k % 10);
	}

     }