Java

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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.CollectionFeature.ALLOWS_NULL_VALUES;
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import com.google.common.annotations.GwtCompatible;
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import com.google.common.annotations.GwtIncompatible;
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import com.google.common.annotations.J2ktIncompatible;
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import com.google.common.collect.testing.Helpers;
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import com.google.common.collect.testing.features.CollectionFeature;
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import com.google.common.collect.testing.features.CollectionSize;
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import java.lang.reflect.Method;
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import java.util.Collection;
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import org.junit.Ignore;
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/**
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 * Tests {@link java.util.Set#hashCode}.
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 *
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 * @author George van den Driessche
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 */
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@GwtCompatible(emulated = true)
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@Ignore // Affects only Android test runner, which respects JUnit 4 annotations on JUnit 3 tests.
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@SuppressWarnings("JUnit4ClassUsedInJUnit3")
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public class SetHashCodeTester<E> extends AbstractSetTester<E> {
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  public void testHashCode() {
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    int expectedHashCode = 0;
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    for (E element : getSampleElements()) {
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      expectedHashCode += ((element == null) ? 0 : element.hashCode());
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    }
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    assertEquals(
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        "A Set's hashCode() should be the sum of those of its elements.",
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        expectedHashCode,
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        getSet().hashCode());
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  }
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  @CollectionSize.Require(absent = CollectionSize.ZERO)
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  @CollectionFeature.Require(ALLOWS_NULL_VALUES)
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  public void testHashCode_containingNull() {
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    Collection<E> elements = getSampleElements(getNumElements() - 1);
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    int expectedHashCode = 0;
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    for (E element : elements) {
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      expectedHashCode += ((element == null) ? 0 : element.hashCode());
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    }
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    elements.add(null);
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    collection = getSubjectGenerator().create(elements.toArray());
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    assertEquals(
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        "A Set's hashCode() should be the sum of those of its elements (with "
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            + "a null element counting as having a hash of zero).",
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        expectedHashCode,
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        getSet().hashCode());
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  }
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  /**
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   * Returns the {@link Method} instances for the test methods in this class which call {@code
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   * hashCode()} on the set values so that set tests on unhashable objects can suppress it with
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   * {@code FeatureSpecificTestSuiteBuilder.suppressing()}.
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   */
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  @J2ktIncompatible
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  @GwtIncompatible // reflection
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  public static Method[] getHashCodeMethods() {
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    return new Method[] {
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      Helpers.getMethod(SetHashCodeTester.class, "testHashCode"),
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      Helpers.getMethod(SetHashCodeTester.class, "testHashCode_containingNull")
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    };
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  }
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}
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