guava

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/*
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 * Copyright (C) 2008 The Guava Authors
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 *
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 * Licensed under the Apache License, Version 2.0 (the "License");
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 * you may not use this file except in compliance with the License.
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 * You may obtain a copy of the License at
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 *
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 * http://www.apache.org/licenses/LICENSE-2.0
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 *
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 * Unless required by applicable law or agreed to in writing, software
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 * distributed under the License is distributed on an "AS IS" BASIS,
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 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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 * See the License for the specific language governing permissions and
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 * limitations under the License.
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 */
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package com.google.common.collect.testing.testers;
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import static com.google.common.collect.testing.features.MapFeature.ALLOWS_NULL_KEYS;
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import static com.google.common.collect.testing.features.MapFeature.ALLOWS_NULL_VALUES;
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import com.google.common.annotations.GwtCompatible;
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import com.google.common.collect.testing.AbstractMapTester;
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import com.google.common.collect.testing.features.CollectionSize;
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import com.google.common.collect.testing.features.MapFeature;
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import java.util.Collection;
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import java.util.Map.Entry;
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import org.junit.Ignore;
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/**
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 * Tests {@link java.util.Map#hashCode}.
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 *
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 * @author George van den Driessche
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 * @author Chris Povirk
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 */
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@GwtCompatible
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@Ignore // Affects only Android test runner, which respects JUnit 4 annotations on JUnit 3 tests.
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public class MapHashCodeTester<K, V> extends AbstractMapTester<K, V> {
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  public void testHashCode() {
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    int expectedHashCode = 0;
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    for (Entry<K, V> entry : getSampleEntries()) {
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      expectedHashCode += hash(entry);
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    }
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    assertEquals(
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        "A Map's hashCode() should be the sum of those of its entries.",
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        expectedHashCode,
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        getMap().hashCode());
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  }
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  @CollectionSize.Require(absent = CollectionSize.ZERO)
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  @MapFeature.Require(ALLOWS_NULL_KEYS)
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  public void testHashCode_containingNullKey() {
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    Entry<K, V> entryWithNull = entry(null, v3());
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    runEntryWithNullTest(entryWithNull);
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  }
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  @CollectionSize.Require(absent = CollectionSize.ZERO)
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  @MapFeature.Require(ALLOWS_NULL_VALUES)
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  public void testHashCode_containingNullValue() {
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    Entry<K, V> entryWithNull = entry(k3(), null);
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    runEntryWithNullTest(entryWithNull);
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  }
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  private void runEntryWithNullTest(Entry<K, V> entryWithNull) {
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    Collection<Entry<K, V>> entries = getSampleEntries(getNumEntries() - 1);
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    entries.add(entryWithNull);
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    int expectedHashCode = 0;
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    for (Entry<K, V> entry : entries) {
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      expectedHashCode += hash(entry);
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    }
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    resetContainer(getSubjectGenerator().create(entries.toArray()));
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    assertEquals(
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        "A Map's hashCode() should be the sum of those of its entries (where "
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            + "a null element in an entry counts as having a hash of zero).",
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        expectedHashCode,
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        getMap().hashCode());
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  }
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  private static int hash(Entry<?, ?> e) {
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    return (e.getKey() == null ? 0 : e.getKey().hashCode())
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        ^ (e.getValue() == null ? 0 : e.getValue().hashCode());
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  }
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}
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