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}