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>ISIN</b> (International Securities Identifying Number) Check Digit calculation/validation. 21 * 22 * <p> 23 * ISIN Numbers are 12 character alphanumeric codes used 24 * to identify Securities. 25 * </p> 26 * 27 * <p> 28 * Check digit calculation uses the <i>Modulus 10 Double Add Double</i> technique 29 * with every second digit being weighted by 2. Alphabetic characters are 30 * converted to numbers by their position in the alphabet starting with A being 10. 31 * Weighted numbers greater than ten are treated as two separate numbers. 32 * </p> 33 * 34 * <p> 35 * See <a href="http://en.wikipedia.org/wiki/ISIN">Wikipedia - ISIN</a> 36 * for more details. 37 * </p> 38 * 39 * @since 1.4 40 */ 41 public final class ISINCheckDigit extends ModulusCheckDigit { 42 43 private static final long serialVersionUID = -1239211208101323599L; 44 45 private static final int MAX_ALPHANUMERIC_VALUE = 35; // Character.getNumericValue('Z') 46 47 /** Singleton ISIN Check Digit instance */ 48 public static final CheckDigit ISIN_CHECK_DIGIT = new ISINCheckDigit(); 49 50 /** weighting given to digits depending on their right position */ 51 private static final int[] POSITION_WEIGHT = {2, 1}; 52 53 /** 54 * Constructs an ISIN Identifier Check Digit routine. 55 */ 56 public ISINCheckDigit() { 57 super(); 58 } 59 60 /** 61 * Calculate the modulus for an ISIN code. 62 * 63 * @param code The code to calculate the modulus for. 64 * @param includesCheckDigit Whether the code includes the Check Digit or not. 65 * @return The modulus value 66 * @throws CheckDigitException if an error occurs calculating the modulus 67 * for the specified code 68 */ 69 @Override 70 protected int calculateModulus(final String code, final boolean includesCheckDigit) throws CheckDigitException { 71 final StringBuilder transformed = new StringBuilder(code.length() * 2); // CHECKSTYLE IGNORE MagicNumber 72 if (includesCheckDigit) { 73 final char checkDigit = code.charAt(code.length() - 1); // fetch the last character 74 if (!Character.isDigit(checkDigit)) { 75 throw new CheckDigitException("Invalid checkdigit[" + checkDigit + "] in " + code); 76 } 77 } 78 for (int i = 0; i < code.length(); i++) { 79 final int charValue = Character.getNumericValue(code.charAt(i)); 80 if (charValue < 0 || charValue > MAX_ALPHANUMERIC_VALUE) { 81 throw new CheckDigitException("Invalid Character[" + (i + 1) + "] = '" + charValue + "'"); 82 } 83 // this converts alphanumerics to two digits 84 // so there is no need to overload toInt() 85 transformed.append(charValue); 86 } 87 return super.calculateModulus(transformed.toString(), includesCheckDigit); 88 } 89 90 /** 91 * <p>Calculates the <i>weighted</i> value of a character in the 92 * code at a specified position.</p> 93 * 94 * <p>For ISIN (from right to left) <b>odd</b> digits are weighted 95 * with a factor of <b>one</b> and <b>even</b> digits with a factor 96 * of <b>two</b>. Weighted values are reduced to their digital root</p> 97 * 98 * @param charValue The numeric value of the character. 99 * @param leftPos The position of the character in the code, counting from left to right 100 * @param rightPos The position of the character in the code, counting from right to left 101 * @return The weighted value of the character. 102 */ 103 @Override 104 protected int weightedValue(final int charValue, final int leftPos, final int rightPos) { 105 final int weight = POSITION_WEIGHT[rightPos % 2]; // CHECKSTYLE IGNORE MagicNumber 106 final int weightedValue = charValue * weight; 107 return ModulusCheckDigit.sumDigits(weightedValue); 108 } 109 }