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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  /**
20   * <b>Check Digit</b> calculation and validation.
21   * <p>
22   * The logic for validating check digits has previously been
23   * embedded within the logic for specific code validation, which
24   * includes other validations such as verifying the format
25   * or length of a code. {@link CheckDigit} provides for separating out
26   * the check digit calculation logic enabling it to be more easily
27   * tested and reused.
28   * <p>
29   * Although Commons Validator is primarily concerned with validation,
30   * {@link CheckDigit} also defines behaviour for calculating/generating check
31   * digits, since it makes sense that users will want to (re-)use the
32   * same logic for both. The {@link org.apache.commons.validator.routines.ISBNValidator}
33   * makes specific use of this feature by providing the facility to validate ISBN-10 codes
34   * and then convert them to the new ISBN-13 standard.
35   * <p>
36   * {@link CheckDigit} is used by the new generic
37   * <a href="..\CodeValidator.html">CodeValidator</a> implementation.
38   * <p>
39   * <h3>Implementations</h3>
40   * See the 
41   * <a href="package-summary.html">Package Summary</a> for a full
42   * list of implementations provided within Commons Validator.
43   *
44   * @see org.apache.commons.validator.routines.CodeValidator
45   * @version $Revision: 589328 $ $Date: 2007-10-28 11:43:47 +0100 (So, 28 Okt 2007) $
46   * @since Validator 1.4
47   */
48  public interface CheckDigit {
49  
50      /**
51       * Calculate the <i>Check Digit</i> for a code.
52       *
53       * @param code The code to calculate the Check Digit for.
54       * @return The calculated Check Digit
55       * @throws CheckDigitException if an error occurs.
56       */
57      public String calculate(String code) throws CheckDigitException;
58  
59      /**
60       * Validate the check digit for the code.
61       *
62       * @param code The code to validate.
63       * @return <code>true</code> if the check digit is valid, otherwise
64       * <code>false</code>.
65       */
66      public boolean isValid(String code);
67  
68  }