    001/*
    002 * Licensed to the Apache Software Foundation (ASF) under one or more
    003 * contributor license agreements.  See the NOTICE file distributed with
    004 * this work for additional information regarding copyright ownership.
    005 * The ASF licenses this file to You under the Apache License, Version 2.0
    006 * (the "License"); you may not use this file except in compliance with
    007 * the License.  You may obtain a copy of the License at
    008 *
    009 *      http://www.apache.org/licenses/LICENSE-2.0
    010 *
    011 * Unless required by applicable law or agreed to in writing, software
    012 * distributed under the License is distributed on an "AS IS" BASIS,
    013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    014 * See the License for the specific language governing permissions and
    015 * limitations under the License.
    016 */
    017package org.apache.commons.validator.routines.checkdigit;
    018
    019import java.io.Serializable;
    020
    021/**
    022 * <b>IBAN</b> (International Bank Account Number) Check Digit calculation/validation.
    023 * <p>
    024 * This routine is based on the ISO 7064 Mod 97,10 check digit calculation routine.
    025 * <p>
    026 * The two check digit characters in a IBAN number are the third and fourth characters
    027 * in the code. For <i>check digit</i> calculation/validation the first four characters are moved
    028 * to the end of the code.
    029 *  So <code>CCDDnnnnnnn</code> becomes <code>nnnnnnnCCDD</code> (where
    030 *  <code>CC</code> is the country code and <code>DD</code> is the check digit). For
    031 *  check digit calculation the check digit value should be set to zero (i.e.
    032 *  <code>CC00nnnnnnn</code> in this example.
    033 * <p>
    034 * Note: the class does not check the format of the IBAN number, only the check digits.
    035 * <p>
    036 * For further information see
    037 *  <a href="http://en.wikipedia.org/wiki/International_Bank_Account_Number">Wikipedia -
    038 *  IBAN number</a>.
    039 *
    040 * @since 1.4
    041 */
    042public final class IBANCheckDigit implements CheckDigit, Serializable {
    043
    044    private static final int MIN_CODE_LEN = 5;
    045
    046    private static final long serialVersionUID = -3600191725934382801L;
    047
    048    private static final int MAX_ALPHANUMERIC_VALUE = 35; // Character.getNumericValue('Z')
    049
    050    /** Singleton IBAN Number Check Digit instance */
    051    public static final CheckDigit IBAN_CHECK_DIGIT = new IBANCheckDigit();
    052
    053    private static final long MAX = 999999999;
    054
    055    private static final long MODULUS = 97;
    056
    057    /**
    058     * Constructs Check Digit routine for IBAN Numbers.
    059     */
    060    public IBANCheckDigit() {
    061    }
    062
    063    /**
    064     * Calculate the <i>Check Digit</i> for an IBAN code.
    065     * <p>
    066     * <b>Note:</b> The check digit is the third and fourth
    067     * characters and is set to the value "<code>00</code>".
    068     *
    069     * @param code The code to calculate the Check Digit for
    070     * @return The calculated Check Digit as 2 numeric decimal characters, e.g. "42"
    071     * @throws CheckDigitException if an error occurs calculating
    072     * the check digit for the specified code
    073     */
    074    @Override
    075    public String calculate(String code) throws CheckDigitException {
    076        if (code == null || code.length() < MIN_CODE_LEN) {
    077            throw new CheckDigitException("Invalid Code length=" + (code == null ? 0 : code.length()));
    078        }
    079        code = code.substring(0, 2) + "00" + code.substring(4); // CHECKSTYLE IGNORE MagicNumber
    080        final int modulusResult = calculateModulus(code);
    081        final int charValue = 98 - modulusResult; // CHECKSTYLE IGNORE MagicNumber
    082        final String checkDigit = Integer.toString(charValue);
    083        return charValue > 9 ? checkDigit : "0" + checkDigit; // CHECKSTYLE IGNORE MagicNumber
    084    }
    085
    086    /**
    087     * Calculate the modulus for a code.
    088     *
    089     * @param code The code to calculate the modulus for.
    090     * @return The modulus value
    091     * @throws CheckDigitException if an error occurs calculating the modulus
    092     * for the specified code
    093     */
    094    private int calculateModulus(final String code) throws CheckDigitException {
    095        final String reformattedCode = code.substring(4) + code.substring(0, 4); // CHECKSTYLE IGNORE MagicNumber
    096        long total = 0;
    097        for (int i = 0; i < reformattedCode.length(); i++) {
    098            final int charValue = Character.getNumericValue(reformattedCode.charAt(i));
    099            if (charValue < 0 || charValue > MAX_ALPHANUMERIC_VALUE) {
    100                throw new CheckDigitException("Invalid Character[" + i + "] = '" + charValue + "'");
    101            }
    102            total = (charValue > 9 ? total * 100 : total * 10) + charValue; // CHECKSTYLE IGNORE MagicNumber
    103            if (total > MAX) {
    104                total = total % MODULUS;
    105            }
    106        }
    107        return (int) (total % MODULUS);
    108    }
    109
    110    /**
    111     * Validate the check digit of an IBAN code.
    112     *
    113     * @param code The code to validate
    114     * @return {@code true} if the check digit is valid, otherwise
    115     * {@code false}
    116     */
    117    @Override
    118    public boolean isValid(final String code) {
    119        if (code == null || code.length() < MIN_CODE_LEN) {
    120            return false;
    121        }
    122        final String check = code.substring(2, 4); // CHECKSTYLE IGNORE MagicNumber
    123        if ("00".equals(check) || "01".equals(check) || "99".equals(check)) {
    124            return false;
    125        }
    126        try {
    127            return calculateModulus(code) == 1;
    128        } catch (final CheckDigitException ex) {
    129            return false;
    130        }
    131    }
    132
    133}