001/*
002 * Copyright 2002-2017 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
019import org.springframework.lang.Nullable;
020
021/**
022 * Instances of a type comparator should be able to compare pairs of objects for equality.
023 * The specification of the return value is the same as for {@link java.lang.Comparable}.
024 *
025 * @author Andy Clement
026 * @since 3.0
027 * @see java.lang.Comparable
028 */
029public interface TypeComparator {
030
031        /**
032         * Return {@code true} if the comparator can compare these two objects.
033         * @param firstObject the first object
034         * @param secondObject the second object
035         * @return {@code true} if the comparator can compare these objects
036         */
037        boolean canCompare(@Nullable Object firstObject, @Nullable Object secondObject);
038
039        /**
040         * Compare two given objects.
041         * @param firstObject the first object
042         * @param secondObject the second object
043         * @return 0 if they are equal, <0 if the first is smaller than the second,
044         * or >0 if the first is larger than the second
045         * @throws EvaluationException if a problem occurs during comparison
046         * (or if they are not comparable in the first place)
047         */
048        int compare(@Nullable Object firstObject, @Nullable Object secondObject) throws EvaluationException;
049
050}