1 /*
2  * Copyright (C) 2009 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 package android.util;
18 
19 import java.util.Objects;
20 
21 /**
22  * Container to ease passing around a tuple of two objects. This object provides a sensible
23  * implementation of equals(), returning true if equals() is true on each of the contained
24  * objects.
25  */
26 public class Pair<F, S> {
27     public final F first;
28     public final S second;
29 
30     /**
31      * Constructor for a Pair.
32      *
33      * @param first the first object in the Pair
34      * @param second the second object in the pair
35      */
Pair(F first, S second)36     public Pair(F first, S second) {
37         this.first = first;
38         this.second = second;
39     }
40 
41     /**
42      * Checks the two objects for equality by delegating to their respective
43      * {@link Object#equals(Object)} methods.
44      *
45      * @param o the {@link Pair} to which this one is to be checked for equality
46      * @return true if the underlying objects of the Pair are both considered
47      *         equal
48      */
49     @Override
equals(Object o)50     public boolean equals(Object o) {
51         if (!(o instanceof Pair)) {
52             return false;
53         }
54         Pair<?, ?> p = (Pair<?, ?>) o;
55         return Objects.equals(p.first, first) && Objects.equals(p.second, second);
56     }
57 
58     /**
59      * Compute a hash code using the hash codes of the underlying objects
60      *
61      * @return a hashcode of the Pair
62      */
63     @Override
hashCode()64     public int hashCode() {
65         return (first == null ? 0 : first.hashCode()) ^ (second == null ? 0 : second.hashCode());
66     }
67 
68     @Override
toString()69     public String toString() {
70         return "Pair{" + String.valueOf(first) + " " + String.valueOf(second) + "}";
71     }
72 
73     /**
74      * Convenience method for creating an appropriately typed pair.
75      * @param a the first object in the Pair
76      * @param b the second object in the pair
77      * @return a Pair that is templatized with the types of a and b
78      */
create(A a, B b)79     public static <A, B> Pair <A, B> create(A a, B b) {
80         return new Pair<A, B>(a, b);
81     }
82 }
83