效验是否为银行卡

public class Test {
 
    public static void main(String[] args) {
        String card = "6227007200120897790";
        System.out.println("      card: " + card);
        System.out.println("check code: " + getBankCardCheckCode(card));
        System.out.println("是否为银行卡:"+checkBankCard(card));
    }
    
    /**
     * 校验银行卡卡号
     * @param cardId
     * @return
     */
    public static boolean checkBankCard(String cardId) {
             char bit = getBankCardCheckCode(cardId.substring(0, cardId.length() - 1));
             if(bit == ‘N‘){
                 return false;
             }
             return cardId.charAt(cardId.length() - 1) == bit;
    }
    
    /**
     * 从不含校验位的银行卡卡号采用 Luhm 校验算法获得校验位
     * @param nonCheckCodeCardId
     * @return
     */
    public static char getBankCardCheckCode(String nonCheckCodeCardId){
        if(nonCheckCodeCardId == null || nonCheckCodeCardId.trim().length() == 0
                || !nonCheckCodeCardId.matches("\\d+")) {
            //如果传的不是数据返回N
            return ‘N‘;
        }
        char[] chs = nonCheckCodeCardId.trim().toCharArray();
        int luhmSum = 0;
        for(int i = chs.length - 1, j = 0; i >= 0; i--, j++) {
            int k = chs[i] - ‘0‘;
            if(j % 2 == 0) {
                k *= 2;
                k = k / 10 + k % 10;
            }
            luhmSum += k;           
        }
        return (luhmSum % 10 == 0) ? ‘0‘ : (char)((10 - luhmSum % 10) + ‘0‘);
    }
}

/**
 * 校验银行卡卡号
 * @param cardId
 * @return
 */
BOOL checkCardNo(NSString* cardNo){
    if ((int)cardNo.length < 13 || (int)cardNo.length > 19) return NO;
    NSString *str = [cardNo substringWithRange:NSMakeRange(0, cardNo.length - 1)];
    int luhmSum = 0;
    for(int i = (int)str.length - 1, j = 0; i >= 0; i--, j++) {
        int k = [str characterAtIndex:i] - ‘0‘;
        if(j % 2 == 0) {
            k *= 2;
            k = k / 10 + k % 10;
        }
        luhmSum += k;
    }
    char bit = (luhmSum % 10 == 0) ? ‘0‘ : (char)((10 - luhmSum % 10) + ‘0‘);
    if(bit == ‘N‘){
        return false;
    }
    return [cardNo characterAtIndex:cardNo.length - 1] == bit;
}