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/*
* Copyright (C) 2008 The Guava Authors
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.common.collect.testing.testers;
import static com.google.common.collect.testing.features.MapFeature.ALLOWS_NULL_KEYS;
import static com.google.common.collect.testing.features.MapFeature.ALLOWS_NULL_VALUES;
import com.google.common.collect.testing.AbstractMapTester;
import com.google.common.collect.testing.features.CollectionSize;
import com.google.common.collect.testing.features.MapFeature;
import java.util.Collection;
import java.util.Map;
/**
* Tests {@link java.util.Map#hashCode}.
*
* <p>This class is GWT compatible.
*
* @author George van den Driessche
* @author Chris Povirk
*/
public class MapHashCodeTester<K, V> extends AbstractMapTester<K, V> {
public void testHashCode() {
int expectedHashCode = 0;
for (Map.Entry<K, V> entry : getSampleEntries()) {
expectedHashCode += hash(entry);
}
assertEquals(
"A Map's hashCode() should be the sum of those of its entries.",
expectedHashCode, getMap().hashCode());
}
@CollectionSize.Require(absent = CollectionSize.ZERO)
@MapFeature.Require(ALLOWS_NULL_KEYS)
public void testHashCode_containingNullKey() {
Map.Entry<K, V> entryWithNull = entry(null, samples.e3.getValue());
runEntryWithNullTest(entryWithNull);
}
@CollectionSize.Require(absent = CollectionSize.ZERO)
@MapFeature.Require(ALLOWS_NULL_VALUES)
public void testHashCode_containingNullValue() {
Map.Entry<K, V> entryWithNull = entry(samples.e3.getKey(), null);
runEntryWithNullTest(entryWithNull);
}
private void runEntryWithNullTest(Map.Entry<K, V> entryWithNull) {
Collection<Map.Entry<K, V>> entries = getSampleEntries(getNumEntries() - 1);
entries.add(entryWithNull);
int expectedHashCode = 0;
for (Map.Entry<K, V> entry : entries) {
expectedHashCode += hash(entry);
}
resetContainer(getSubjectGenerator().create(entries.toArray()));
assertEquals(
"A Map's hashCode() should be the sum of those of its entries (where "
+ "a null element in an entry counts as having a hash of zero).",
expectedHashCode, getMap().hashCode());
}
private static int hash(Map.Entry<?, ?> e) {
return (e.getKey() == null ? 0 : e.getKey().hashCode())
^ (e.getValue() == null ? 0 : e.getValue().hashCode());
}
}
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