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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  import java.io.Serializable;
20  
21  /**
22   * <b>IBAN</b> (International Bank Account Number) Check Digit calculation/validation.
23   * <p>
24   * This routine is based on the ISO 7064 Mod 97,10 check digit calculation routine.
25   * <p>
26   * The two check digit characters in a IBAN number are the third and fourth characters
27   * in the code. For <i>check digit</i> calculation/validation the first four characters are moved
28   * to the end of the code.
29   *  So <code>CCDDnnnnnnn</code> becomes <code>nnnnnnnCCDD</code> (where
30   *  <code>CC</code> is the country code and <code>DD</code> is the check digit). For
31   *  check digit calcualtion the check digit value should be set to zero (i.e.
32   *  <code>CC00nnnnnnn</code> in this example.
33   * <p>
34   * Note: the class does not check the format of the IBAN number, only the check digits.
35   * <p>
36   * For further information see
37   *  <a href="http://en.wikipedia.org/wiki/International_Bank_Account_Number">Wikipedia -
38   *  IBAN number</a>.
39   *
40   * @version $Revision: 1441399 $ $Date: 2013-02-01 12:48:59 +0100 (Fr, 01 Feb 2013) $
41   * @since Validator 1.4
42   */
43  public final class IBANCheckDigit implements CheckDigit, Serializable {
44  
45      private static final long serialVersionUID = -3600191725934382801L;
46  
47      /** Singleton IBAN Number Check Digit instance */
48      public static final CheckDigit IBAN_CHECK_DIGIT = new IBANCheckDigit();
49  
50      private static final long MAX = 999999999;
51  
52      private static final long MODULUS = 97;
53  
54      /**
55       * Construct Check Digit routine for IBAN Numbers.
56       */
57      public IBANCheckDigit() {
58      }
59  
60      /**
61       * Validate the check digit of an IBAN code.
62       *
63       * @param code The code to validate
64       * @return <code>true</code> if the check digit is valid, otherwise
65       * <code>false</code>
66       */
67      public boolean isValid(String code) {
68          if (code == null || code.length() < 5) {
69              return false;
70          }
71          try {
72              int modulusResult = calculateModulus(code);
73              return (modulusResult == 1);
74          } catch (CheckDigitException  ex) {
75              return false;
76          }
77      }
78  
79      /**
80       * Calculate the <i>Check Digit</i> for an IBAN code.
81       * <p>
82       * <b>Note:</b> The check digit is the third and fourth
83       * characters and and should contain value "<code>00</code>".
84       *
85       * @param code The code to calculate the Check Digit for
86       * @return The calculated Check Digit as 2 numeric decimal characters, e.g. "42"
87       * @throws CheckDigitException if an error occurs calculating
88       * the check digit for the specified code
89       */
90      public String calculate(String code) throws CheckDigitException {
91          if (code == null || code.length() < 5) {
92              throw new CheckDigitException("Invalid Code length=" +
93                      (code == null ? 0 : code.length()));
94          }
95          int modulusResult = calculateModulus(code);
96          int charValue = (98 - modulusResult);
97          String checkDigit = Integer.toString(charValue);
98          return (charValue > 9 ? checkDigit : "0" + checkDigit);
99      }
100 
101     /**
102      * Calculate the modulus for a code.
103      *
104      * @param code The code to calculate the modulus for.
105      * @return The modulus value
106      * @throws CheckDigitException if an error occurs calculating the modulus
107      * for the specified code
108      */
109     private int calculateModulus(String code) throws CheckDigitException {
110         String reformattedCode = code.substring(4) + code.substring(0, 4);
111         long total = 0;
112         for (int i = 0; i < reformattedCode.length(); i++) {
113             int charValue = Character.getNumericValue(reformattedCode.charAt(i));
114             if (charValue < 0 || charValue > 35) {
115                 throw new CheckDigitException("Invalid Character[" +
116                         i + "] = '" + charValue + "'");
117             }
118             total = (charValue > 9 ? total * 100 : total * 10) + charValue;
119             if (total > MAX) {
120                 total = (total % MODULUS);
121             }
122         }
123         return (int)(total % MODULUS);
124     }
125 
126 }