ValidateCard.java

package cfy.connection;

public class ValidateCard {
	public static final int INVALID = -1;
	public static final int VISA = 0;
	public static final int MASTERCARD = 1;
	public static final int AMERICAN_EXPRESS = 2;
	public static final int EN_ROUTE = 3;
	public static final int DINERS_CLUB = 4;

	private static final String[] cardNames = { "Visa", "Mastercard", "American Express", "En Route",
			"Diner's CLub/Carte Blanche", };

	/**
	 * Valid a Credit Card number
	 */
	public boolean validCC(String number) throws Exception {
		int CardID;
		if ((CardID = getCardID(number)) != -1)
			return validCCNumber(number);
		return false;
	}

	/**
	 * Get the Card type returns the credit card type INVALID = -1; VISA = 0;
	 * MASTERCARD = 1; AMERICAN_EXPRESS = 2; EN_ROUTE = 3; DINERS_CLUB = 4;
	 */
	public int getCardID(String number) {
		int valid = INVALID;

		String digit1 = number.substring(0, 1);
		String digit2 = number.substring(0, 2);
		String digit3 = number.substring(0, 3);
		String digit4 = number.substring(0, 4);

		if (isNumber(number)) {
			/*
			 * ---- VISA prefix=4 ---- length=13 or 16 (can be 15 too!?! maybe)
			 */
			if (digit1.equals("4")) {
				if (number.length() == 13 || number.length() == 16)
					valid = VISA;
			}
			/*
			 * ---------- MASTERCARD prefix= 51 ... 55 ---------- length= 16
			 */
			else if (digit2.compareTo("51") >= 0 && digit2.compareTo("55") <= 0) {
				if (number.length() == 16)
					valid = MASTERCARD;
			}
			
			
			
			/*
			 * ---- AMEX prefix=34 or 37 ---- length=15
			 */
			else if (digit2.equals("34") || digit2.equals("37")) {
				if (number.length() == 15)
					valid = AMERICAN_EXPRESS;
			}
			/*
			 * ----- ENROU prefix=2014 or 2149 ----- length=15
			 */
			else if (digit4.equals("2014") || digit4.equals("2149")) {
				if (number.length() == 15)
					valid = EN_ROUTE;
			}
			/*
			 * ----- DCLUB prefix=300 ... 305 or 36 or 38 ----- length=14
			 */
			else if (digit2.equals("36") || digit2.equals("38")
					|| (digit3.compareTo("300") >= 0 && digit3.compareTo("305") <= 0)) {
				if (number.length() == 14)
					valid = DINERS_CLUB;
			}
		}
		return valid;

		/*
		 * ---- DISCOVER card prefix = 60 -------- lenght = 16 left as an exercise ...
		 */

	}

	public boolean isNumber(String n) {
		try {
			double d = Double.valueOf(n).doubleValue();
			return true;
		} catch (NumberFormatException e) {
			e.printStackTrace();
			return false;
		}
	}

	public String getCardName(int id) {
		return (id > -1 && id < cardNames.length ? cardNames[id] : "");
	}

	public boolean validCCNumber(String n) {
		try {
			/*
			 ** known as the LUHN Formula (mod10)
			 */
			int j = n.length();

			String[] s1 = new String[j];
			for (int i = 0; i < n.length(); i++)
				s1[i] = "" + n.charAt(i);

			int checksum = 0;

			for (int i = s1.length - 1; i >= 0; i -= 2) {
				int k = 0;

				if (i > 0) {
					k = Integer.valueOf(s1[i - 1]).intValue() * 2;
					if (k > 9) {
						String s = "" + k;
						k = Integer.valueOf(s.substring(0, 1)).intValue() + Integer.valueOf(s.substring(1)).intValue();
					}
					checksum += Integer.valueOf(s1[i]).intValue() + k;
				} else
					checksum += Integer.valueOf(s1[0]).intValue();
			}
			return ((checksum % 10) == 0);
		} catch (Exception e) {
			e.printStackTrace();
			return false;
		}
	}
}