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