1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17 package org.apache.commons.validator.routines.checkdigit;
18
19 /**
20 * Modulus 11 <b>ISBN-10</b> Check Digit calculation/validation.
21 * <p>
22 * ISBN-10 Numbers are a numeric code except for the last (check) digit
23 * which can have a value of "X".
24 * <p>
25 * Check digit calculation is based on <i>modulus 11</i> with digits being weighted
26 * based by their position, from right to left with the first digit being weighted
27 * 1, the second 2 and so on. If the check digit is calculated as "10" it is converted
28 * to "X".
29 * <p>
30 * <b>N.B.</b> From 1st January 2007 the book industry will start to use a new 13 digit
31 * ISBN number (rather than this 10 digit ISBN number) which uses the EAN-13 / UPC
32 * (see {@link EAN13CheckDigit}) standard.
33 * <p>
34 * For further information see:
35 * <ul>
36 * <li><a href="http://en.wikipedia.org/wiki/ISBN">Wikipedia - International
37 * Standard Book Number (ISBN)</a>.</li>
38 * <li><a href="http://www.isbn.org/standards/home/isbn/transition.asp">ISBN-13
39 * Transition details</a>.</li>
40 * </ul>
41 *
42 * @version $Revision: 1227719 $ $Date: 2012-01-05 12:45:51 -0500 (Thu, 05 Jan 2012) $
43 * @since Validator 1.4
44 */
45 public final class ISBN10CheckDigit extends ModulusCheckDigit {
46
47 private static final long serialVersionUID = 8000855044504864964L;
48
49 /** Singleton ISBN-10 Check Digit instance */
50 public static final CheckDigit ISBN10_CHECK_DIGIT = new ISBN10CheckDigit();
51
52 /**
53 * Construct a modulus 11 Check Digit routine for ISBN-10.
54 */
55 public ISBN10CheckDigit() {
56 super(11);
57 }
58
59 /**
60 * Calculates the <i>weighted</i> value of a charcter in the
61 * code at a specified position.
62 *
63 * <p>For ISBN-10 (from right to left) digits are weighted
64 * by their position.</p>
65 *
66 * @param charValue The numeric value of the character.
67 * @param leftPos The position of the character in the code, counting from left to right
68 * @param rightPos The positionof the character in the code, counting from right to left
69 * @return The weighted value of the character.
70 */
71 protected int weightedValue(int charValue, int leftPos, int rightPos) {
72 return (charValue * rightPos);
73 }
74
75 /**
76 * <p>Convert a character at a specified position to an
77 * integer value.</p>
78 *
79 * <p>Character 'X' check digit converted to 10.</p>
80 *
81 * @param character The character to convert.
82 * @param leftPos The position of the character in the code, counting from left to right
83 * @param rightPos The positionof the character in the code, counting from right to left
84 * @return The integer value of the character.
85 * @throws CheckDigitException if an error occurs.
86 */
87 protected int toInt(char character, int leftPos, int rightPos)
88 throws CheckDigitException {
89 if (rightPos == 1 && character == 'X') {
90 return 10;
91 } else {
92 return super.toInt(character, leftPos, rightPos);
93 }
94 }
95
96 /**
97 * <p>Convert an integer value to a character at a specified position.</p>
98 *
99 * <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 }