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 import org.apache.commons.functor.UnaryFunction;
24 import org.apache.commons.functor.adapter.RightBoundFunction;
25
26 /**
27 * Adapts a {@link Comparator Comparator} to the
28 * {@link BinaryFunction} interface.
29 *
30 * @version $Revision: 1166355 $ $Date: 2011-09-07 21:54:29 +0200 (Wed, 07 Sep 2011) $
31 * @author Rodney Waldhoff
32 */
33 public final class Min<T> implements BinaryFunction<T, T, T>, Serializable {
34
35 /**
36 * Basic Min instance.
37 */
38 public static final Min<Comparable<?>> INSTANCE = Min.<Comparable<?>>instance();
39
40 /**
41 * serialVersionUID declaration.
42 */
43 private static final long serialVersionUID = 9190170976707323848L;
44
45 private final Comparator<T> comparator;
46
47 /**
48 * Create a new Min.
49 */
50 @SuppressWarnings("unchecked")
51 public Min() {
52 this(ComparableComparator.instance());
53 }
54
55 /**
56 * Create a new Min.
57 * @param comparator to use
58 */
59 public Min(Comparator<T> comparator) {
60 if (comparator == null) {
61 throw new IllegalArgumentException("Comparator argument must not be null");
62 }
63 this.comparator = comparator;
64 }
65
66 /**
67 * {@inheritDoc}
68 */
69 public T evaluate(T left, T right) {
70 return (comparator.compare(left, right) <= 0) ? left : right;
71 }
72
73 /**
74 * {@inheritDoc}
75 */
76 public boolean equals(Object that) {
77 return that == this || (that instanceof Min<?> && equals((Min<?>) that));
78 }
79
80 /**
81 * Learn whether another Min is equal to this.
82 * @param that Min to test
83 * @return boolean
84 */
85 public boolean equals(Min<?> that) {
86 return null != that && comparator.equals(that.comparator);
87 }
88
89 /**
90 * {@inheritDoc}
91 */
92 public int hashCode() {
93 return "Min".hashCode() ^ comparator.hashCode();
94 }
95
96 /**
97 * {@inheritDoc}
98 */
99 public String toString() {
100 return "Min<" + comparator + ">";
101 }
102
103 /**
104 * Get a basic Min instance.
105 * @return Min
106 */
107 public static <T extends Comparable<?>> Min<T> instance() {
108 return new Min<T>();
109 }
110
111 /**
112 * Get a Min UnaryFunction.
113 * @param right the right side argument of the Min function
114 * @return UnaryFunction<T, T>
115 */
116 public static <T extends Comparable<?>> UnaryFunction<T, T> instance(T right) {
117 return RightBoundFunction.bind(new Min<T>(), right);
118 }
119
120 }