| // Copyright 2014 Google Inc. All rights reserved. |
| // |
| // Licensed under the Apache License, Version 2.0 (the "License"); |
| // you may not use this file except in compliance with the License. |
| // You may obtain a copy of the License at |
| // |
| // http://www.apache.org/licenses/LICENSE-2.0 |
| // |
| // Unless required by applicable law or agreed to in writing, software |
| // distributed under the License is distributed on an "AS IS" BASIS, |
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| // See the License for the specific language governing permissions and |
| // limitations under the License. |
| package com.google.devtools.build.lib.util; |
| |
| import com.google.common.base.Function; |
| |
| import java.util.Comparator; |
| import java.util.Objects; |
| |
| import javax.annotation.Nullable; |
| |
| /** |
| * An immutable, semantic-free ordered pair of nullable values. Avoid using it in public APIs. |
| */ |
| public final class Pair<A, B> { |
| |
| /** |
| * Creates a new pair containing the given elements in order. |
| */ |
| public static <A, B> Pair<A, B> of(@Nullable A first, @Nullable B second) { |
| return new Pair<>(first, second); |
| } |
| |
| /** |
| * The first element of the pair. |
| */ |
| @Nullable |
| public final A first; |
| |
| /** |
| * The second element of the pair. |
| */ |
| @Nullable |
| public final B second; |
| |
| /** |
| * Constructor. It is usually easier to call {@link #of}. |
| */ |
| public Pair(@Nullable A first, @Nullable B second) { |
| this.first = first; |
| this.second = second; |
| } |
| |
| @Nullable |
| public A getFirst() { |
| return first; |
| } |
| |
| @Nullable |
| public B getSecond() { |
| return second; |
| } |
| |
| @Override |
| public String toString() { |
| return "(" + first + ", " + second + ")"; |
| } |
| |
| @Override |
| public boolean equals(Object o) { |
| if (this == o) { |
| return true; |
| } |
| if (!(o instanceof Pair)) { |
| return false; |
| } |
| Pair<?, ?> p = (Pair<?, ?>) o; |
| return Objects.equals(first, p.first) && Objects.equals(second, p.second); |
| } |
| |
| @Override |
| public int hashCode() { |
| return Objects.hash(first, second); |
| } |
| |
| /** |
| * A function that maps to the first element in a pair. |
| */ |
| public static <A, B> Function<Pair<A, B>, A> firstFunction() { |
| return new Function<Pair<A, B>, A>() { |
| @Override |
| public A apply(Pair<A, B> pair) { |
| return pair.first; |
| } |
| }; |
| } |
| |
| /** |
| * A function that maps to the second element in a pair. |
| */ |
| public static <A, B> Function<Pair<A, B>, B> secondFunction() { |
| return new Function<Pair<A, B>, B>() { |
| @Override |
| public B apply(Pair<A, B> pair) { |
| return pair.second; |
| } |
| }; |
| } |
| |
| /** |
| * A comparator that compares pairs by comparing the first element. |
| */ |
| public static <T extends Comparable<T>, B> Comparator<Pair<T, B>> compareByFirst() { |
| return new Comparator<Pair<T, B>>() { |
| @Override |
| public int compare(Pair<T, B> o1, Pair<T, B> o2) { |
| return o1.first.compareTo(o2.first); |
| } |
| }; |
| } |
| } |