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="https://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 * @since 1.4
43 */
44 public final class ISBN10CheckDigit extends ModulusCheckDigit {
45
46 private static final long serialVersionUID = 8000855044504864964L;
47
48 /** Singleton ISBN-10 Check Digit instance */
49 public static final CheckDigit ISBN10_CHECK_DIGIT = new ISBN10CheckDigit();
50
51 /**
52 * Constructs a modulus 11 Check Digit routine for ISBN-10.
53 */
54 public ISBN10CheckDigit() {
55 super(MODULUS_11);
56 }
57
58 /**
59 * <p>Convert an integer value to a character at a specified position.</p>
60 *
61 * <p>Value '10' for position 1 (check digit) converted to 'X'.</p>
62 *
63 * @param charValue The integer value of the character.
64 * @return The converted character.
65 * @throws CheckDigitException if an error occurs.
66 */
67 @Override
68 protected String toCheckDigit(final int charValue)
69 throws CheckDigitException {
70 if (charValue == 10) { // CHECKSTYLE IGNORE MagicNumber
71 return "X";
72 }
73 return super.toCheckDigit(charValue);
74 }
75
76 /**
77 * <p>Convert a character at a specified position to an
78 * integer value.</p>
79 *
80 * <p>Character 'X' check digit converted to 10.</p>
81 *
82 * @param character The character to convert.
83 * @param leftPos The position of the character in the code, counting from left to right
84 * @param rightPos The position of the character in the code, counting from right to left
85 * @return The integer value of the character.
86 * @throws CheckDigitException if an error occurs.
87 */
88 @Override
89 protected int toInt(final char character, final int leftPos, final int rightPos)
90 throws CheckDigitException {
91 if (rightPos == 1 && character == 'X') {
92 return 10; // CHECKSTYLE IGNORE MagicNumber
93 }
94 return super.toInt(character, leftPos, rightPos);
95 }
96
97 /**
98 * Calculates the <i>weighted</i> value of a character in the
99 * code at a specified position.
100 *
101 * <p>For ISBN-10 (from right to left) digits are weighted
102 * by their position.</p>
103 *
104 * @param charValue The numeric value of the character.
105 * @param leftPos The position of the character in the code, counting from left to right
106 * @param rightPos The positionof the character in the code, counting from right to left
107 * @return The weighted value of the character.
108 */
109 @Override
110 protected int weightedValue(final int charValue, final int leftPos, final int rightPos) {
111 return charValue * rightPos;
112 }
113
114 }