1 /*
2 * Copyright 2002-2013 the original author or authors.
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 package org.springframework.expression;
18
19 /**
20 * Instances of a type comparator should be able to compare pairs of objects for equality.
21 * The specification of the return value is the same as for {@link java.lang.Comparable}.
22 *
23 * @author Andy Clement
24 * @since 3.0
25 * @see java.lang.Comparable
26 */
27 public interface TypeComparator {
28
29 /**
30 * Return {@code true} if the comparator can compare these two objects.
31 * @param firstObject the first object
32 * @param secondObject the second object
33 * @return {@code true} if the comparator can compare these objects
34 */
35 boolean canCompare(Object firstObject, Object secondObject);
36
37 /**
38 * Compare two given objects.
39 * @param firstObject the first object
40 * @param secondObject the second object
41 * @return 0 if they are equal, <0 if the first is smaller than the second,
42 * or >0 if the first is larger than the second
43 * @throws EvaluationException if a problem occurs during comparison
44 * (or if they are not comparable in the first place)
45 */
46 int compare(Object firstObject, Object secondObject) throws EvaluationException;
47
48 }