1/*
2 * Copyright (C) 2008 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.collect.testing.testers;
18
19import static com.google.common.collect.testing.features.MapFeature.ALLOWS_NULL_KEYS;
20import static com.google.common.collect.testing.features.MapFeature.ALLOWS_NULL_VALUES;
21
22import com.google.common.collect.testing.AbstractMapTester;
23import com.google.common.collect.testing.features.CollectionSize;
24import com.google.common.collect.testing.features.MapFeature;
25
26import java.util.Collection;
27import java.util.Map;
28
29/**
30 * Tests {@link java.util.Map#hashCode}.
31 *
32 * <p>This class is GWT compatible.
33 *
34 * @author George van den Driessche
35 * @author Chris Povirk
36 */
37public class MapHashCodeTester<K, V> extends AbstractMapTester<K, V> {
38  public void testHashCode() {
39    int expectedHashCode = 0;
40    for (Map.Entry<K, V> entry : getSampleEntries()) {
41      expectedHashCode += hash(entry);
42    }
43    assertEquals(
44        "A Map's hashCode() should be the sum of those of its entries.",
45        expectedHashCode, getMap().hashCode());
46  }
47
48  @CollectionSize.Require(absent = CollectionSize.ZERO)
49  @MapFeature.Require(ALLOWS_NULL_KEYS)
50  public void testHashCode_containingNullKey() {
51    Map.Entry<K, V> entryWithNull = entry(null, samples.e3.getValue());
52    runEntryWithNullTest(entryWithNull);
53  }
54
55  @CollectionSize.Require(absent = CollectionSize.ZERO)
56  @MapFeature.Require(ALLOWS_NULL_VALUES)
57  public void testHashCode_containingNullValue() {
58    Map.Entry<K, V> entryWithNull = entry(samples.e3.getKey(), null);
59    runEntryWithNullTest(entryWithNull);
60  }
61
62  private void runEntryWithNullTest(Map.Entry<K, V> entryWithNull) {
63    Collection<Map.Entry<K, V>> entries = getSampleEntries(getNumEntries() - 1);
64
65    entries.add(entryWithNull);
66
67    int expectedHashCode = 0;
68    for (Map.Entry<K, V> entry : entries) {
69      expectedHashCode += hash(entry);
70    }
71
72    resetContainer(getSubjectGenerator().create(entries.toArray()));
73    assertEquals(
74        "A Map's hashCode() should be the sum of those of its entries (where "
75            + "a null element in an entry counts as having a hash of zero).",
76        expectedHashCode, getMap().hashCode());
77  }
78
79  private static int hash(Map.Entry<?, ?> e) {
80    return (e.getKey() == null ? 0 : e.getKey().hashCode())
81        ^ (e.getValue() == null ? 0 : e.getValue().hashCode());
82  }
83}
84