    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
    019/**
    020 * International Standard Serial Number (ISSN)
    021 * is an eight-digit serial number used to
    022 * uniquely identify a serial publication.
    023 * <pre>
    024 * The format is:
    025 *
    026 * ISSN dddd-dddC
    027 * where:
    028 * d = decimal digit (0-9)
    029 * C = checksum (0-9 or X)
    030 *
    031 * The checksum is formed by adding the first 7 digits multiplied by
    032 * the position in the entire number (counting from the right).
    033 * For example, abcd-efg would be 8a + 7b + 6c + 5d + 4e +3f +2g.
    034 * The check digit is modulus 11, where the value 10 is represented by 'X'
    035 * For example:
    036 * ISSN 0317-8471
    037 * ISSN 1050-124X
    038 * </pre>
    039 * <p>
    040 * <b>Note:</b> This class expects the input to be numeric only,
    041 * with all formatting removed.
    042 * For example:
    043 * <pre>
    044 * 03178471
    045 * 1050124X
    046 * </pre>
    047 * @since 1.5.0
    048 */
    049public final class ISSNCheckDigit extends ModulusCheckDigit {
    050
    051
    052    private static final long serialVersionUID = 1L;
    053
    054    /** Singleton ISSN Check Digit instance */
    055    public static final CheckDigit ISSN_CHECK_DIGIT = new ISSNCheckDigit();
    056
    057    /**
    058     * Creates the instance using a checkdigit modulus of 11
    059     */
    060    public ISSNCheckDigit() {
    061        super(11); // CHECKSTYLE IGNORE MagicNumber
    062    }
    063
    064    @Override
    065    protected int weightedValue(int charValue, int leftPos, int rightPos) throws CheckDigitException {
    066        return charValue * (9 - leftPos); // CHECKSTYLE IGNORE MagicNumber
    067    }
    068
    069    @Override
    070    protected String toCheckDigit(int charValue) throws CheckDigitException {
    071        if (charValue == 10) { // CHECKSTYLE IGNORE MagicNumber
    072            return "X";
    073        }
    074        return super.toCheckDigit(charValue);
    075    }
    076
    077    @Override
    078    protected int toInt(char character, int leftPos, int rightPos)
    079            throws CheckDigitException {
    080        if (rightPos == 1 && character == 'X') {
    081            return 10; // CHECKSTYLE IGNORE MagicNumber
    082        }
    083        return super.toInt(character, leftPos, rightPos);
    084    }
    085}