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    private static final long serialVersionUID = 1L;
052
053    /** Singleton ISSN Check Digit instance */
054    public static final CheckDigit ISSN_CHECK_DIGIT = new ISSNCheckDigit();
055
056    /**
057     * Creates the instance using a checkdigit modulus of 11.
058     */
059    public ISSNCheckDigit() {
060        super(MODULUS_11);
061    }
062
063    @Override
064    protected String toCheckDigit(final int charValue) throws CheckDigitException {
065        if (charValue == 10) { // CHECKSTYLE IGNORE MagicNumber
066            return "X";
067        }
068        return super.toCheckDigit(charValue);
069    }
070
071    @Override
072    protected int toInt(final char character, final int leftPos, final int rightPos)
073            throws CheckDigitException {
074        if (rightPos == 1 && character == 'X') {
075            return 10; // CHECKSTYLE IGNORE MagicNumber
076        }
077        return super.toInt(character, leftPos, rightPos);
078    }
079
080    @Override
081    protected int weightedValue(final int charValue, final int leftPos, final int rightPos) throws CheckDigitException {
082        return charValue * (9 - leftPos); // CHECKSTYLE IGNORE MagicNumber
083    }
084}