PairwiseEquivalence.java revision 1d580d0f6ee4f21eb309ba7b509d2c6d671c4044 
1/*
2 * Copyright (C) 2011 The Guava Authors
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 com.google.common.base;
18
19import com.google.common.annotations.GwtCompatible;
20
21import java.io.Serializable;
22import java.util.Iterator;
23
24import javax.annotation.Nullable;
25
26@GwtCompatible(serializable = true)
27final class PairwiseEquivalence<T> extends Equivalence<Iterable<T>>
28    implements Serializable {
29
30  final Equivalence<? super T> elementEquivalence;
31
32  PairwiseEquivalence(Equivalence<? super T> elementEquivalence) {
33    this.elementEquivalence = Preconditions.checkNotNull(elementEquivalence);
34  }
35
36  @Override
37  protected boolean doEquivalent(Iterable<T> iterableA, Iterable<T> iterableB) {
38    Iterator<T> iteratorA = iterableA.iterator();
39    Iterator<T> iteratorB = iterableB.iterator();
40
41    while (iteratorA.hasNext() && iteratorB.hasNext()) {
42      if (!elementEquivalence.equivalent(iteratorA.next(), iteratorB.next())) {
43        return false;
44      }
45    }
46
47    return !iteratorA.hasNext() && !iteratorB.hasNext();
48  }
49
50  @Override
51  protected int doHash(Iterable<T> iterable) {
52    int hash = 78721;
53    for (T element : iterable) {
54      hash = hash * 24943 + elementEquivalence.hash(element);
55    }
56    return hash;
57  }
58
59  @Override
60  public boolean equals(@Nullable Object object) {
61    if (object instanceof PairwiseEquivalence) {
62      PairwiseEquivalence<?> that = (PairwiseEquivalence<?>) object;
63      return this.elementEquivalence.equals(that.elementEquivalence);
64    }
65
66    return false;
67  }
68
69  @Override
70  public int hashCode() {
71    return elementEquivalence.hashCode() ^ 0x46a3eb07;
72  }
73
74  @Override
75  public String toString() {
76    return elementEquivalence + ".pairwise()";
77  }
78
79  private static final long serialVersionUID = 1;
80}
81