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 * https://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
18 /*
19 * This is not the original file distributed by the Apache Software Foundation
20 * It has been modified by the Hipparchus project
21 */
22 package org.hipparchus.util;
23
24
25 /**
26 * Generic pair.
27 * <p>
28 * Although the instances of this class are immutable, it is impossible
29 * to ensure that the references passed to the constructor will not be
30 * modified by the caller.
31 *
32 * @param <K> Key type.
33 * @param <V> Value type.
34 */
35 public class Pair<K, V> {
36 /** Key. */
37 private final K key;
38 /** Value. */
39 private final V value;
40
41 /**
42 * Create an entry representing a mapping from the specified key to the
43 * specified value.
44 *
45 * @param k Key (first element of the pair).
46 * @param v Value (second element of the pair).
47 */
48 public Pair(K k, V v) {
49 key = k;
50 value = v;
51 }
52
53 /**
54 * Create an entry representing the same mapping as the specified entry.
55 *
56 * @param entry Entry to copy.
57 */
58 public Pair(Pair<? extends K, ? extends V> entry) {
59 this(entry.getKey(), entry.getValue());
60 }
61
62 /**
63 * Get the key.
64 *
65 * @return the key (first element of the pair).
66 */
67 public K getKey() {
68 return key;
69 }
70
71 /**
72 * Get the value.
73 *
74 * @return the value (second element of the pair).
75 */
76 public V getValue() {
77 return value;
78 }
79
80 /**
81 * Get the first element of the pair.
82 *
83 * @return the first element of the pair.
84 */
85 public K getFirst() {
86 return key;
87 }
88
89 /**
90 * Get the second element of the pair.
91 *
92 * @return the second element of the pair.
93 */
94 public V getSecond() {
95 return value;
96 }
97
98 /**
99 * Compare the specified object with this entry for equality.
100 *
101 * @param o Object.
102 * @return {@code true} if the given object is also a map entry and
103 * the two entries represent the same mapping.
104 */
105 @Override
106 public boolean equals(Object o) {
107 if (this == o) {
108 return true;
109 }
110 if (!(o instanceof Pair)) {
111 return false;
112 }
113 Pair<?, ?> other = (Pair<?, ?>) o;
114 return (key == null ? other.key == null :
115 key.equals(other.key)) &&
116 (value == null ? other.value == null :
117 value.equals(other.value));
118 }
119
120 /**
121 * Compute a hash code.
122 *
123 * @return the hash code value.
124 */
125 @Override
126 public int hashCode() {
127 int result = key == null ? 0 : key.hashCode();
128
129 final int h = value == null ? 0 : value.hashCode();
130 result = 37 * result + h ^ (h >>> 16);
131
132 return result;
133 }
134
135 /** {@inheritDoc} */
136 @Override
137 public String toString() {
138 return "[" + getKey() + ", " + getValue() + "]";
139 }
140
141 /**
142 * Convenience factory method that calls the
143 * {@link #Pair(Object, Object) constructor}.
144 *
145 * @param <K> the key type
146 * @param <V> the value type
147 * @param k First element of the pair.
148 * @param v Second element of the pair.
149 * @return a new {@code Pair} containing {@code k} and {@code v}.
150 */
151 public static <K, V> Pair<K, V> create(K k, V v) {
152 return new Pair<K, V>(k, v);
153 }
154 }