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.CollectionFeature.FAILS_FAST_ON_CONCURRENT_MODIFICATION;
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import static com.google.common.collect.testing.features.CollectionFeature.SUPPORTS_REMOVE;
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import static com.google.common.collect.testing.features.CollectionSize.SEVERAL;
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import static com.google.common.collect.testing.features.CollectionSize.ZERO;
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import com.google.common.annotations.GwtCompatible;
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import com.google.common.collect.testing.AbstractCollectionTester;
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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.util.ConcurrentModificationException;
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import java.util.Iterator;
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import org.junit.Ignore;
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/**
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 * A generic JUnit test which tests {@code clear()} operations on a collection. Can't be invoked
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 * directly; please see {@link com.google.common.collect.testing.CollectionTestSuiteBuilder}.
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 *
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 * @author George van den Driessche
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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 CollectionClearTester<E> extends AbstractCollectionTester<E> {
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  @CollectionFeature.Require(SUPPORTS_REMOVE)
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  public void testClear() {
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    collection.clear();
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    assertTrue("After clear(), a collection should be empty.", collection.isEmpty());
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    assertEquals(0, collection.size());
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    assertFalse(collection.iterator().hasNext());
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  }
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  @CollectionFeature.Require(absent = SUPPORTS_REMOVE)
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  @CollectionSize.Require(absent = ZERO)
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  public void testClear_unsupported() {
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    try {
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      collection.clear();
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      fail(
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          "clear() should throw UnsupportedOperation if a collection does "
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              + "not support it and is not empty.");
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    } catch (UnsupportedOperationException expected) {
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    }
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    expectUnchanged();
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  }
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  @CollectionFeature.Require(absent = SUPPORTS_REMOVE)
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  @CollectionSize.Require(ZERO)
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  public void testClear_unsupportedByEmptyCollection() {
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    try {
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      collection.clear();
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    } catch (UnsupportedOperationException tolerated) {
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    }
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    expectUnchanged();
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  }
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  @CollectionFeature.Require({SUPPORTS_REMOVE, FAILS_FAST_ON_CONCURRENT_MODIFICATION})
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  @CollectionSize.Require(SEVERAL)
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  public void testClearConcurrentWithIteration() {
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    try {
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      Iterator<E> iterator = collection.iterator();
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      collection.clear();
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      iterator.next();
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      /*
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       * We prefer for iterators to fail immediately on hasNext, but ArrayList
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       * and LinkedList will notably return true on hasNext here!
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       */
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      fail("Expected ConcurrentModificationException");
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    } catch (ConcurrentModificationException expected) {
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      // success
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    }
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  }
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}
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