判斷銀行卡號格式是否正確

/**
 * Created by Administrator on 2016/9/18.
 * 驗證銀行卡格式是否正確
 */
public class CheckIdCard {
    /**
     * 校驗銀行卡卡號
     *
     * @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;
    }

    /**
     * 從不含校驗位的銀行卡卡號采用 Luhm 校驗算法獲得校驗位
     *
     * @param nonCheckCodeCardId
     * @return
     */
    public static char getBankCardCheckCode(String nonCheckCodeCardId) {
        if (nonCheckCodeCardId == null
                || nonCheckCodeCardId.trim().length() == 0
                || !nonCheckCodeCardId.matches("\\d+")) {
            // 如果傳的不是數據返回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');
    }
}