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 10 <b>EAN-13</b> / <b>UPC</b> / <b>ISBN-13</b> Check Digit
21 * calculation/validation.
22 * <p>
23 * Check digit calculation is based on <i>modulus 10</i> with digits in
24 * an <i>odd</i> position (from right to left) being weighted 1 and <i>even</i>
25 * position digits being weighted 3.
26 * <p>
27 * For further information see:
28 * <ul>
29 * <li>EAN-13 - see
30 * <a href="https://en.wikipedia.org/wiki/European_Article_Number">Wikipedia -
31 * European Article Number</a>.</li>
32 * <li>UPC - see
33 * <a href="https://en.wikipedia.org/wiki/Universal_Product_Code">Wikipedia -
34 * Universal Product Code</a>.</li>
35 * <li>ISBN-13 - see
36 * <a href="https://en.wikipedia.org/wiki/ISBN">Wikipedia - International
37 * Standard Book Number (ISBN)</a>.</li>
38 * </ul>
39 *
40 * @since 1.4
41 */
42 public final class EAN13CheckDigit extends ModulusCheckDigit {
43
44 private static final long serialVersionUID = 1726347093230424107L;
45
46 /** Singleton EAN-13 Check Digit instance */
47 public static final CheckDigit EAN13_CHECK_DIGIT = new EAN13CheckDigit();
48
49 /** Weighting given to digits depending on their right position */
50 private static final int[] POSITION_WEIGHT = {3, 1};
51
52 /**
53 * Constructs a modulus 10 Check Digit routine for EAN/UPC.
54 */
55 public EAN13CheckDigit() {
56 }
57
58 /**
59 * <p>Calculates the <i>weighted</i> value of a character in the
60 * code at a specified position.</p>
61 *
62 * <p>For EAN-13 (from right to left) <b>odd</b> digits are weighted
63 * with a factor of <b>one</b> and <b>even</b> digits with a factor
64 * of <b>three</b>.</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 @Override
72 protected int weightedValue(final int charValue, final int leftPos, final int rightPos) {
73 return charValue * POSITION_WEIGHT[rightPos % 2];
74 }
75 }