001/*
002 * Copyright 2002-2013 the original author or authors.
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 *      https://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package org.springframework.expression;
018
019/**
020 * Instances of a type comparator should be able to compare pairs of objects for equality.
021 * The specification of the return value is the same as for {@link java.lang.Comparable}.
022 *
023 * @author Andy Clement
024 * @since 3.0
025 * @see java.lang.Comparable
026 */
027public interface TypeComparator {
028
029        /**
030         * Return {@code true} if the comparator can compare these two objects.
031         * @param firstObject the first object
032         * @param secondObject the second object
033         * @return {@code true} if the comparator can compare these objects
034         */
035        boolean canCompare(Object firstObject, Object secondObject);
036
037        /**
038         * Compare two given objects.
039         * @param firstObject the first object
040         * @param secondObject the second object
041         * @return 0 if they are equal, <0 if the first is smaller than the second,
042         * or >0 if the first is larger than the second
043         * @throws EvaluationException if a problem occurs during comparison
044         * (or if they are not comparable in the first place)
045         */
046        int compare(Object firstObject, Object secondObject) throws EvaluationException;
047
048}