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 */
017package org.apache.commons.validator.routines.checkdigit;
018
019/**
020 * <b>Check Digit</b> calculation and validation.
021 * <p>
022 * The logic for validating check digits has previously been
023 * embedded within the logic for specific code validation, which
024 * includes other validations such as verifying the format
025 * or length of a code. {@link CheckDigit} provides for separating out
026 * the check digit calculation logic enabling it to be more easily
027 * tested and reused.
028 * </p>
029 * <p>
030 * Although Commons Validator is primarily concerned with validation,
031 * {@link CheckDigit} also defines behavior for calculating/generating check
032 * digits, since it makes sense that users will want to (re-)use the
033 * same logic for both. The {@link org.apache.commons.validator.routines.ISBNValidator}
034 * makes specific use of this feature by providing the facility to validate ISBN-10 codes
035 * and then convert them to the new ISBN-13 standard.
036 * </p>
037 * <p>
038 * CheckDigit is used by the new generic @link CodeValidator} implementation.
039 * </p>
040 *
041 * <h2>Implementations</h2>
042 * See the 
043 * <a href="package-summary.html">Package Summary</a> for a full
044 * list of implementations provided within Commons Validator.
045 *
046 * @see org.apache.commons.validator.routines.CodeValidator
047 * @version $Revision$
048 * @since Validator 1.4
049 */
050public interface CheckDigit {
051
052    /**
053     * Calculates the <i>Check Digit</i> for a code.
054     *
055     * @param code The code to calculate the Check Digit for.
056     * The string must not include the check digit
057     * @return The calculated Check Digit
058     * @throws CheckDigitException if an error occurs.
059     */
060    String calculate(String code) throws CheckDigitException;
061
062    /**
063     * Validates the check digit for the code.
064     *
065     * @param code The code to validate, the string must include the check digit.
066     * @return <code>true</code> if the check digit is valid, otherwise
067     * <code>false</code>.
068     */
069    boolean isValid(String code);
070
071}