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 */
017 package org.apache.commons.validator.routines.checkdigit;
018
019 import java.io.Serializable;
020
021 /**
022 * Modulus 11 <b>ISBN-10</b> Check Digit calculation/validation.
023 * <p>
024 * ISBN-10 Numbers are a numeric code except for the last (check) digit
025 * which can have a value of "X".
026 * <p>
027 * Check digit calculation is based on <i>modulus 11</i> with digits being weighted
028 * based by their position, from right to left with the first digit being weighted
029 * 1, the second 2 and so on. If the check digit is calculated as "10" it is converted
030 * to "X".
031 * <p>
032 * <b>N.B.</b> From 1st January 2007 the book industry will start to use a new 13 digit
033 * ISBN number (rather than this 10 digit ISBN number) which uses the EAN-13 / UPC
034 * (see {@link EAN13CheckDigit}) standard.
035 * <p>
036 * For further information see:
037 * <ul>
038 * <li><a href="http://en.wikipedia.org/wiki/ISBN">Wikipedia - International
039 * Standard Book Number (ISBN)</a>.</li>
040 * <li><a href="http://www.isbn.org/standards/home/isbn/transition.asp">ISBN-13
041 * Transition details</a>.</li>
042 * </ul>
043 *
044 * @version $Revision: 493905 $ $Date: 2007-01-08 03:11:38 +0100 (Mo, 08. Jan 2007) $
045 * @since Validator 1.4
046 */
047 public final class ISBN10CheckDigit extends ModulusCheckDigit implements Serializable {
048
049 /** Singleton ISBN-10 Check Digit instance */
050 public static final CheckDigit INSTANCE = new ISBN10CheckDigit();
051
052 /**
053 * Construct a modulus 11 Check Digit routine for ISBN-10.
054 */
055 public ISBN10CheckDigit() {
056 super(11);
057 }
058
059 /**
060 * Calculates the <i>weighted</i> value of a charcter in the
061 * code at a specified position.
062 *
063 * <p>For ISBN-10 (from right to left) digits are weighted
064 * by their position.</p>
065 *
066 * @param charValue The numeric value of the character.
067 * @param leftPos The position of the character in the code, counting from left to right
068 * @param rightPos The positionof the character in the code, counting from right to left
069 * @return The weighted value of the character.
070 */
071 protected int weightedValue(int charValue, int leftPos, int rightPos) {
072 return (charValue * rightPos);
073 }
074
075 /**
076 * <p>Convert a character at a specified position to an
077 * integer value.</p>
078 *
079 * <p>Character 'X' check digit converted to 10.</p>
080 *
081 * @param character The character to convert.
082 * @param leftPos The position of the character in the code, counting from left to right
083 * @param rightPos The positionof the character in the code, counting from right to left
084 * @return The integer value of the character.
085 * @throws CheckDigitException if an error occurs.
086 */
087 protected int toInt(char character, int leftPos, int rightPos)
088 throws CheckDigitException {
089 if (rightPos == 1 && character == 'X') {
090 return 10;
091 } else {
092 return super.toInt(character, leftPos, rightPos);
093 }
094 }
095
096 /**
097 * <p>Convert an integer value to a character at a specified position.</p>
098 *
099 * <p>Value '10' for position 1 (check digit) converted to 'X'.</p>
100 *
101 * @param charValue The integer value of the character.
102 * @return The converted character.
103 * @throws CheckDigitException if an error occurs.
104 */
105 protected String toCheckDigit(int charValue)
106 throws CheckDigitException {
107 if (charValue == 10) {
108 return "X";
109 } else {
110 return super.toCheckDigit(charValue);
111 }
112 }
113
114 }