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/*
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* Copyright (c) 2017, 2019, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package jdk.internal.vm.compiler.collections;
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import java.util.Objects;
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/**
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* Utility class representing a pair of values.
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*
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* @since 19.0
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*/
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public final class Pair<L, R> {
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private static final Pair<Object, Object> EMPTY = new Pair<>(null, null);
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private final L left;
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private final R right;
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/**
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* Returns an empty pair.
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*
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* @since 19.0
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*/
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@SuppressWarnings("unchecked")
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public static <L, R> Pair<L, R> empty() {
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return (Pair<L, R>) EMPTY;
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}
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/**
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* Constructs a pair with its left value being {@code left}, or returns an empty pair if
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* {@code left} is null.
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*
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* @return the constructed pair or an empty pair if {@code left} is null.
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* @since 19.0
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*/
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public static <L, R> Pair<L, R> createLeft(L left) {
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if (left == null) {
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return empty();
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} else {
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return new Pair<>(left, null);
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}
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}
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/**
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* Constructs a pair with its right value being {@code right}, or returns an empty pair if
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* {@code right} is null.
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*
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* @return the constructed pair or an empty pair if {@code right} is null.
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* @since 19.0
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*/
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public static <L, R> Pair<L, R> createRight(R right) {
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if (right == null) {
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return empty();
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} else {
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return new Pair<>(null, right);
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}
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}
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/**
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* Constructs a pair with its left value being {@code left}, and its right value being
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* {@code right}, or returns an empty pair if both inputs are null.
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*
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* @return the constructed pair or an empty pair if both inputs are null.
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* @since 19.0
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*/
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public static <L, R> Pair<L, R> create(L left, R right) {
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if (right == null && left == null) {
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return empty();
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} else {
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return new Pair<>(left, right);
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}
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}
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private Pair(L left, R right) {
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this.left = left;
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this.right = right;
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}
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/**
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* Returns the left value of this pair.
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*
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* @since 19.0
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*/
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public L getLeft() {
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return left;
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}
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/**
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* Returns the right value of this pair.
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*
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* @since 19.0
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*/
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public R getRight() {
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return right;
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}
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/**
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* {@inheritDoc}
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*
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* @since 19.0
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*/
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@Override
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public int hashCode() {
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return Objects.hashCode(left) + 31 * Objects.hashCode(right);
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}
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/**
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* {@inheritDoc}
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*
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* @since 19.0
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*/
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@SuppressWarnings("unchecked")
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@Override
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public boolean equals(Object obj) {
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if (obj == this) {
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return true;
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}
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if (obj instanceof Pair) {
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Pair<L, R> pair = (Pair<L, R>) obj;
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return Objects.equals(left, pair.left) && Objects.equals(right, pair.right);
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}
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return false;
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}
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/**
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* {@inheritDoc}
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*
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* @since 19.0
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*/
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@Override
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public String toString() {
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return String.format("(%s, %s)", left, right);
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}
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}
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