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 }