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 10 <b>EAN-13</b> / <b>UPC</b> / <b>ISBN-13</b> Check Digit
023 * calculation/validation.
024 * <p>
025 * Check digit calculation is based on <i>modulus 10</i> with digits in
026 * an <i>odd</i> position (from right to left) being weighted 1 and <i>even</i>
027 * position digits being weighted 3.
028 * <p>
029 * For further information see:
030 * <ul>
031 * <li>EAN-13 - see
032 * <a href="http://en.wikipedia.org/wiki/European_Article_Number">Wikipedia -
033 * European Article Number</a>.</li>
034 * <li>UPC - see
035 * <a href="http://en.wikipedia.org/wiki/Universal_Product_Code">Wikipedia -
036 * Universal Product Code</a>.</li>
037 * <li>ISBN-13 - see
038 * <a href="http://en.wikipedia.org/wiki/ISBN">Wikipedia - International
039 * Standard Book Number (ISBN)</a>.</li>
040 * </ul>
041 *
042 * @version $Revision: 493905 $ $Date: 2007-01-08 03:11:38 +0100 (Mo, 08. Jan 2007) $
043 * @since Validator 1.4
044 */
045 public final class EAN13CheckDigit extends ModulusCheckDigit implements Serializable {
046
047 /** Singleton EAN-13 Check Digit instance */
048 public static final CheckDigit INSTANCE = new EAN13CheckDigit();
049
050 /** weighting given to digits depending on their right position */
051 private static final int[] POSITION_WEIGHT = new int[] {3, 1};
052
053 /**
054 * Construct a modulus 10 Check Digit routine for EAN/UPC.
055 */
056 public EAN13CheckDigit() {
057 super(10);
058 }
059
060 /**
061 * <p>Calculates the <i>weighted</i> value of a character in the
062 * code at a specified position.</p>
063 *
064 * <p>For EAN-13 (from right to left) <b>odd</b> digits are weighted
065 * with a factor of <b>one</b> and <b>even</b> digits with a factor
066 * of <b>three</b>.</p>
067 *
068 * @param charValue The numeric value of the character.
069 * @param leftPos The position of the character in the code, counting from left to right
070 * @param rightPos The positionof the character in the code, counting from right to left
071 * @return The weighted value of the character.
072 */
073 protected int weightedValue(int charValue, int leftPos, int rightPos) {
074 int weight = POSITION_WEIGHT[rightPos % 2];
075 return (charValue * weight);
076 }
077 }