1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17 package org.apache.commons.functor.core.comparator;
18
19 import java.io.Serializable;
20 import java.util.Comparator;
21
22 import org.apache.commons.functor.BinaryFunction;
23
24 /**
25 * Adapts a {@link Comparator Comparator} to the
26 * {@link BinaryFunction} interface.
27 *
28 * @version $Revision: 1156349 $ $Date: 2011-08-10 22:21:14 +0200 (Wed, 10 Aug 2011) $
29 * @author Rodney Waldhoff
30 */
31 public final class ComparatorFunction<T> implements BinaryFunction<T, T, Integer>, Serializable {
32
33 /**
34 * Basic ComparatorFunction instance.
35 */
36 public static final ComparatorFunction<Comparable<?>> INSTANCE = ComparatorFunction.<Comparable<?>>instance();
37
38 /**
39 * serialVersionUID declaration.
40 */
41 private static final long serialVersionUID = 1642024869929206095L;
42
43 private final Comparator<? super T> comparator;
44
45 /**
46 * Create a new ComparatorFunction.
47 * @param comparator to wrap
48 */
49 public ComparatorFunction(Comparator<? super T> comparator) {
50 if (comparator == null) {
51 throw new IllegalArgumentException("Comparator must not be null");
52 }
53 this.comparator = comparator;
54 }
55
56 /**
57 * {@inheritDoc}
58 */
59 public Integer evaluate(T left, T right) {
60 return Integer.valueOf(comparator.compare(left, right));
61 }
62
63 /**
64 * {@inheritDoc}
65 */
66 public boolean equals(Object that) {
67 return that == this || (that instanceof ComparatorFunction<?> && equals((ComparatorFunction<?>) that));
68 }
69
70 /**
71 * Learn whether a specified ComparatorFunction is equal to this.
72 * @param that the ComparatorFunction to test
73 * @return boolean
74 */
75 public boolean equals(ComparatorFunction<?> that) {
76 return null != that && comparator.equals(that.comparator);
77 }
78
79 /**
80 * {@inheritDoc}
81 */
82 public int hashCode() {
83 return "ComparatorFunction".hashCode() ^ comparator.hashCode();
84 }
85
86 /**
87 * {@inheritDoc}
88 */
89 public String toString() {
90 return "ComparatorFunction<" + comparator + ">";
91 }
92
93 /**
94 * Get a basic ComparatorFunction instance.
95 * @return ComparatorFunction
96 */
97 @SuppressWarnings("unchecked")
98 public static <T> ComparatorFunction<T> instance() {
99 return new ComparatorFunction<T>(ComparableComparator.INSTANCE);
100 }
101 }