/**
 * Validates a credit card numer.
 * @author Apache Ah64
 */
public class CreditCardValidator {
	
	/**
	 * The credit card numbers.
	 */
	private static final String[] CC_CARDS = new String[] {
        "378282246310005",
        "371449635398431",
        "378734493671000",
        "5610591081018250",
        "30569309025904",
        "38520000023237",
        "6011111111111117",
        "6011000990139424",
        "3530111333300000",
        "3566002020360505",
        "5555555555554444",
        "5105105105105100",
        "4111111111111111",
        "4012888888881881",
        "4222222222222",
        "4417123456789113"
	};

	/**
	 * The main method.
	 * @param args The arguments.
	 */
	public static void main(String[] args) {
		for(int i = 0; i < CC_CARDS.length; i++) {
			final String number = CC_CARDS[i];
			System.out.println("Credit card number: "+number+" is "+(!isValid(number.toCharArray()) ? "in" : "")+"valid");
		}
	}
	
	/**
	 * Check for a valid credit card number.
	 * @param number The credit card number.
	 * @return If the credit card number is valid {@code true}.
	 */
	private static boolean isValid(char[] numbers) {
		int sum = 0, len = numbers.length, d, i;
		final boolean div_two_z = len % 2 == 0;
        for (i = len - 1; i >= 0; i--) {
                d = (numbers[i] - '0') * ((div_two_z ? i % 2 == 0 : i % 2 != 0) ? 2 : 1);
                sum += d > 9 ? d / 10 + d % 10 : d;
        }
        return sum % 10 == 0;
	}
}