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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 org.apache.commons.validator.routines.CodeValidator;
20  
21  /**
22   * <b>Check Digit</b> calculation and validation.
23   * <p>
24   * The logic for validating check digits has previously been
25   * embedded within the logic for specific code validation, which
26   * includes other validations such as verifying the format
27   * or length of a code. {@link CheckDigit} provides for separating out
28   * the check digit calculation logic enabling it to be more easily
29   * tested and reused.
30   * </p>
31   * <p>
32   * Although Commons Validator is primarily concerned with validation,
33   * {@link CheckDigit} also defines behavior for calculating/generating check
34   * digits, since it makes sense that users will want to (re-)use the
35   * same logic for both. The {@link org.apache.commons.validator.routines.ISBNValidator}
36   * makes specific use of this feature by providing the facility to validate ISBN-10 codes
37   * and then convert them to the new ISBN-13 standard.
38   * </p>
39   * <p>
40   * CheckDigit is used by the new generic {@link CodeValidator} implementation.
41   * </p>
42   *
43   * <h2>Implementations</h2>
44   * See the
45   * <a href="package-summary.html">Package Summary</a> for a full
46   * list of implementations provided within Commons Validator.
47   *
48   * @see org.apache.commons.validator.routines.CodeValidator
49   * @since 1.4
50   */
51  public interface CheckDigit {
52  
53      /**
54       * Calculates the <i>Check Digit</i> for a code.
55       *
56       * @param code The code to calculate the Check Digit for.
57       * The string must not include the check digit
58       * @return The calculated Check Digit
59       * @throws CheckDigitException if an error occurs.
60       */
61      String calculate(String code) throws CheckDigitException;
62  
63      /**
64       * Validates the check digit for the code.
65       *
66       * @param code The code to validate, the string must include the check digit.
67       * @return {@code true} if the check digit is valid, otherwise
68       * {@code false}.
69       */
70      boolean isValid(String code);
71  
72  }