Pair.java revision d4a1d2e14297a3387fdb5761090961e714370492 
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
17package android.util;
18
19/**
20 * Container to ease passing around a tuple of two objects. This object provides a sensible
21 * implementation of equals(), returning true if equals() is true on each of the contained
22 * objects.
23 */
24public class Pair<F, S> {
25    public final F first;
26    public final S second;
27
28    /**
29     * Constructor for a Pair. If either are null then equals() and hashCode() will throw
30     * a NullPointerException.
31     * @param first the first object in the Pair
32     * @param second the second object in the pair
33     */
34    public Pair(F first, S second) {
35        this.first = first;
36        this.second = second;
37    }
38
39    /**
40     * Checks the two objects for equality by delegating to their respective equals() methods.
41     * @param o the Pair to which this one is to be checked for equality
42     * @return true if the underlying objects of the Pair are both considered equals()
43     */
44    public boolean equals(Object o) {
45        if (o == this) return true;
46        if (!(o instanceof Pair)) return false;
47        final Pair<F, S> other;
48        try {
49            other = (Pair<F, S>) o;
50        } catch (ClassCastException e) {
51            return false;
52        }
53        return first.equals(other.first) && second.equals(other.second);
54    }
55
56    /**
57     * Compute a hash code using the hash codes of the underlying objects
58     * @return a hashcode of the Pair
59     */
60    public int hashCode() {
61        int result = 17;
62        result = 31 * result + first.hashCode();
63        result = 31 * result + second.hashCode();
64        return result;
65    }
66
67    /**
68     * Convenience method for creating an appropriately typed pair.
69     * @param a the first object in the Pair
70     * @param b the second object in the pair
71     * @return a Pair that is templatized with the types of a and b
72     */
73    public static <A, B> Pair <A, B> create(A a, B b) {
74        return new Pair<A, B>(a, b);
75    }
76}
77