1 /* 2 * Copyright (c) 2017, 2017, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 */ 23 24 25 package jdk.internal.vm.compiler.collections; 26 27 import java.util.Objects; 28 29 /** 30 * Utility class representing a pair of values. 31 * 32 * @since 1.0 33 */ 34 public final class Pair<L, R> { 35 36 private static final Pair<Object, Object> EMPTY = new Pair<>(null, null); 37 38 private final L left; 39 private final R right; 40 41 /** 42 * Returns an empty pair. 43 * 44 * @since 1.0 45 */ 46 @SuppressWarnings("unchecked") empty()47 public static <L, R> Pair<L, R> empty() { 48 return (Pair<L, R>) EMPTY; 49 } 50 51 /** 52 * Constructs a pair with its left value being {@code left}, or returns an empty pair if 53 * {@code left} is null. 54 * 55 * @return the constructed pair or an empty pair if {@code left} is null. 56 * @since 1.0 57 */ createLeft(L left)58 public static <L, R> Pair<L, R> createLeft(L left) { 59 if (left == null) { 60 return empty(); 61 } else { 62 return new Pair<>(left, null); 63 } 64 } 65 66 /** 67 * Constructs a pair with its right value being {@code right}, or returns an empty pair if 68 * {@code right} is null. 69 * 70 * @return the constructed pair or an empty pair if {@code right} is null. 71 * @since 1.0 72 */ createRight(R right)73 public static <L, R> Pair<L, R> createRight(R right) { 74 if (right == null) { 75 return empty(); 76 } else { 77 return new Pair<>(null, right); 78 } 79 } 80 81 /** 82 * Constructs a pair with its left value being {@code left}, and its right value being 83 * {@code right}, or returns an empty pair if both inputs are null. 84 * 85 * @return the constructed pair or an empty pair if both inputs are null. 86 * @since 1.0 87 */ create(L left, R right)88 public static <L, R> Pair<L, R> create(L left, R right) { 89 if (right == null && left == null) { 90 return empty(); 91 } else { 92 return new Pair<>(left, right); 93 } 94 } 95 Pair(L left, R right)96 private Pair(L left, R right) { 97 this.left = left; 98 this.right = right; 99 } 100 101 /** 102 * Returns the left value of this pair. 103 * 104 * @since 1.0 105 */ getLeft()106 public L getLeft() { 107 return left; 108 } 109 110 /** 111 * Returns the right value of this pair. 112 * 113 * @since 1.0 114 */ getRight()115 public R getRight() { 116 return right; 117 } 118 119 /** 120 * {@inheritDoc} 121 * 122 * @since 1.0 123 */ 124 @Override hashCode()125 public int hashCode() { 126 return Objects.hashCode(left) + 31 * Objects.hashCode(right); 127 } 128 129 /** 130 * {@inheritDoc} 131 * 132 * @since 1.0 133 */ 134 @SuppressWarnings("unchecked") 135 @Override equals(Object obj)136 public boolean equals(Object obj) { 137 if (obj == this) { 138 return true; 139 } 140 141 if (obj instanceof Pair) { 142 Pair<L, R> pair = (Pair<L, R>) obj; 143 return Objects.equals(left, pair.left) && Objects.equals(right, pair.right); 144 } 145 146 return false; 147 } 148 149 /** 150 * {@inheritDoc} 151 * 152 * @since 1.0 153 */ 154 @Override toString()155 public String toString() { 156 return String.format("(%s, %s)", left, right); 157 } 158 } 159