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="http://en.wikipedia.org/wiki/European_Article_Number">Wikipedia -
31 * European Article Number</a>.</li>
32 * <li>UPC - see
33 * <a href="http://en.wikipedia.org/wiki/Universal_Product_Code">Wikipedia -
34 * Universal Product Code</a>.</li>
35 * <li>ISBN-13 - see
36 * <a href="http://en.wikipedia.org/wiki/ISBN">Wikipedia - International
37 * Standard Book Number (ISBN)</a>.</li>
38 * </ul>
39 *
40 * @version $Revision: 1227719 $ $Date: 2012-01-05 12:45:51 -0500 (Thu, 05 Jan 2012) $
41 * @since Validator 1.4
42 */
43 public final class EAN13CheckDigit extends ModulusCheckDigit {
44
45 private static final long serialVersionUID = 1726347093230424107L;
46
47 /** Singleton EAN-13 Check Digit instance */
48 public static final CheckDigit EAN13_CHECK_DIGIT = new EAN13CheckDigit();
49
50 /** weighting given to digits depending on their right position */
51 private static final int[] POSITION_WEIGHT = new int[] {3, 1};
52
53 /**
54 * Construct a modulus 10 Check Digit routine for EAN/UPC.
55 */
56 public EAN13CheckDigit() {
57 super(10);
58 }
59
60 /**
61 * <p>Calculates the <i>weighted</i> value of a character in the
62 * code at a specified position.</p>
63 *
64 * <p>For EAN-13 (from right to left) <b>odd</b> digits are weighted
65 * with a factor of <b>one</b> and <b>even</b> digits with a factor
66 * of <b>three</b>.</p>
67 *
68 * @param charValue The numeric value of the character.
69 * @param leftPos The position of the character in the code, counting from left to right
70 * @param rightPos The positionof the character in the code, counting from right to left
71 * @return The weighted value of the character.
72 */
73 protected int weightedValue(int charValue, int leftPos, int rightPos) {
74 int weight = POSITION_WEIGHT[rightPos % 2];
75 return (charValue * weight);
76 }
77 }