信用卡校验位算法THE LUHN MOD-10


信用卡校验位算法THE LUHN MOD-10 http://blogread.cn/it/article/6324?f=wb


import org.apache.commons.lang3.StringUtils;

public class CreditCardValidator {

	/**
	 * 1. 对卡号上的每位数字乘以权重。其规则是,如果卡号数字个数是偶数,则第一位乘以2,否则就乘以1,然后以后分别是,1,2,1,2,1,2;
	 * 
	 * 2. 如果每位数字乘以权重后超过9 ,则需要减去 9;
	 * 
	 * 3. 将所有的处理过的加权数字求和,用 数字 10 求模运算;
	 * 
	 * 4. 余数应该是0,否则可能是输入错误。也可能是一个假号。
	 * 
	 * @param cardNo
	 * @return
	 */
	public static boolean isValid(String cardNo) {
		if (StringUtils.isBlank(cardNo) || !StringUtils.isNumeric(cardNo)) 
			return false;
		int len = cardNo.length();
		boolean isOdd = len % 2 == 1;
		int total = 0;
		int tem = 0;
		for (int i = 0; i < len; i++) {
			tem = Integer.valueOf(String.valueOf(cardNo.charAt(i)));
			if (i == 0 && !isOdd) {

				tem = tem << 1;

			} else if (i > 0 && i % 2 == 0) {

				tem = tem << 1;

			}

			if (tem > 9)
				tem = tem - 9;
			total = total + tem;
		}
		return total % 10 == 0;
	}

}


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