1 /*
2 * Copyright (c) 2017, 2018, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * The Universal Permissive License (UPL), Version 1.0
6 *
7 * Subject to the condition set forth below, permission is hereby granted to any
8 * person obtaining a copy of this software, associated documentation and/or
9 * data (collectively the "Software"), free of charge and under any and all
10 * copyright rights in the Software, and any and all patent rights owned or
11 * freely licensable by each licensor hereunder covering either (i) the
12 * unmodified Software as contributed to or provided by such licensor, or (ii)
13 * the Larger Works (as defined below), to deal in both
14 *
15 * (a) the Software, and
16 *
17 * (b) any piece of software and/or hardware listed in the lrgrwrks.txt file if
18 * one is included with the Software each a "Larger Work" to which the Software
19 * is contributed by such licensors),
20 *
21 * without restriction, including without limitation the rights to copy, create
22 * derivative works of, display, perform, and distribute the Software and make,
23 * use, sell, offer for sale, import, export, have made, and have sold the
24 * Software and the Larger Work(s), and to sublicense the foregoing rights on
25 * either these or other terms.
26 *
27 * This license is subject to the following condition:
28 *
29 * The above copyright notice and either this complete permission notice or at a
30 * minimum a reference to the UPL must be included in all copies or substantial
31 * portions of the Software.
32 *
33 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
34 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
35 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
36 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
37 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
38 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
39 * SOFTWARE.
40 */
41 package jdk.internal.vm.compiler.collections;
42
43 import java.util.Objects;
44
45 /**
46 * Utility class representing a pair of values.
47 *
48 * @since 1.0
49 */
50 public final class Pair<L, R> {
51
52 private static final Pair<Object, Object> EMPTY = new Pair<>(null, null);
53
54 private final L left;
55 private final R right;
56
57 /**
58 * Returns an empty pair.
59 *
60 * @since 1.0
61 */
62 @SuppressWarnings("unchecked")
63 public static <L, R> Pair<L, R> empty() {
64 return (Pair<L, R>) EMPTY;
65 }
66
67 /**
68 * Constructs a pair with its left value being {@code left}, or returns an empty pair if
69 * {@code left} is null.
70 *
71 * @return the constructed pair or an empty pair if {@code left} is null.
72 * @since 1.0
73 */
74 public static <L, R> Pair<L, R> createLeft(L left) {
75 if (left == null) {
76 return empty();
77 } else {
78 return new Pair<>(left, null);
79 }
80 }
81
82 /**
83 * Constructs a pair with its right value being {@code right}, or returns an empty pair if
84 * {@code right} is null.
85 *
86 * @return the constructed pair or an empty pair if {@code right} is null.
87 * @since 1.0
88 */
89 public static <L, R> Pair<L, R> createRight(R right) {
90 if (right == null) {
91 return empty();
92 } else {
93 return new Pair<>(null, right);
94 }
95 }
96
97 /**
98 * Constructs a pair with its left value being {@code left}, and its right value being
99 * {@code right}, or returns an empty pair if both inputs are null.
100 *
101 * @return the constructed pair or an empty pair if both inputs are null.
102 * @since 1.0
103 */
104 public static <L, R> Pair<L, R> create(L left, R right) {
105 if (right == null && left == null) {
106 return empty();
107 } else {
108 return new Pair<>(left, right);
109 }
110 }
111
112 private Pair(L left, R right) {
113 this.left = left;
114 this.right = right;
115 }
116
117 /**
118 * Returns the left value of this pair.
119 *
120 * @since 1.0
121 */
122 public L getLeft() {
123 return left;
124 }
125
126 /**
127 * Returns the right value of this pair.
128 *
129 * @since 1.0
130 */
131 public R getRight() {
132 return right;
133 }
134
135 /**
136 * {@inheritDoc}
137 *
138 * @since 1.0
139 */
140 @Override
141 public int hashCode() {
142 return Objects.hashCode(left) + 31 * Objects.hashCode(right);
143 }
144
145 /**
146 * {@inheritDoc}
147 *
148 * @since 1.0
149 */
150 @SuppressWarnings("unchecked")
151 @Override
152 public boolean equals(Object obj) {
153 if (obj == this) {
154 return true;
155 }
156
157 if (obj instanceof Pair) {
158 Pair<L, R> pair = (Pair<L, R>) obj;
159 return Objects.equals(left, pair.left) && Objects.equals(right, pair.right);
160 }
161
162 return false;
163 }
164
165 /**
166 * {@inheritDoc}
167 *
168 * @since 1.0
169 */
170 @Override
171 public String toString() {
172 return String.format("(%s, %s)", left, right);
173 }
174 }