[LANG-653] Added ConstantInitializer class
git-svn-id: https://svn.apache.org/repos/asf/commons/proper/lang/trunk@1026485 13f79535-47bb-0310-9956-ffa450edef68
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Oliver Heger
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/*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership.
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* The ASF licenses this file to You under the Apache License, Version 2.0
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* (the "License"); you may not use this file except in compliance with
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* the License. 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 org.apache.commons.lang3.concurrent;
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import org.apache.commons.lang3.ObjectUtils;
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/**
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* <p>
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* A very simple implementation of the {@link ConcurrentInitializer} interface
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* which always returns the same object.
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* </p>
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* <p>
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* An instance of this class is passed a reference to an object when it is
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* constructed. The {@link #get()} method just returns this object. No
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* synchronization is required.
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* </p>
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* <p>
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* This class is useful for instance for unit testing or in cases where a
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* specific object has to be passed to an object which expects a
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* {@link ConcurrentInitializer}.
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* </p>
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*
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* @author Apache Software Foundation
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* @version $Id$
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* @param <T> the type of the object managed by this initializer
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*/
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public class ConstantInitializer<T> implements ConcurrentInitializer<T> {
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/** Constant for the format of the string representation. */
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private static final String FMT_TO_STRING = "ConstantInitializer@%d [ object = %s ]";
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/** Stores the managed object. */
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private final T object;
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/**
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* Creates a new instance of {@code ConstantInitializer} and initializes it
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* with the object to be managed. The {@code get()} method will always
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* return the object passed here. This class does not place any restrictions
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* on the object. It may be <b>null</b>, then {@code get()} will return
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* <b>null</b>, too.
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*
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* @param obj the object to be managed by this initializer
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*/
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public ConstantInitializer(T obj) {
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object = obj;
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}
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/**
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* Directly returns the object that was passed to the constructor. This is
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* the same object as returned by {@code get()}. However, this method does
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* not declare that it throws an exception.
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*
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* @return the object managed by this initializer
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*/
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public final T getObject() {
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return object;
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}
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/**
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* Returns the object managed by this initializer. This implementation just
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* returns the object passed to the constructor.
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*
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* @return the object managed by this initializer
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* @throws ConcurrentException if an error occurs
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*/
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public T get() throws ConcurrentException {
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return getObject();
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}
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/**
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* Returns a hash code for this object. This implementation returns the hash
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* code of the managed object.
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*
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* @return a hash code for this object
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*/
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@Override
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public int hashCode() {
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return (getObject() != null) ? getObject().hashCode() : 0;
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}
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/**
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* Compares this object with another one. This implementation returns
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* <b>true</b> if and only if the passed in object is an instance of
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* {@code ConstantInitializer} which refers to an object equals to the
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* object managed by this instance.
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*
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* @param obj the object to compare to
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* @return a flag whether the objects are equal
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*/
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@Override
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public boolean equals(Object obj) {
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if (this == obj) {
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return true;
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}
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if (!(obj instanceof ConstantInitializer<?>)) {
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return false;
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}
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ConstantInitializer<?> c = (ConstantInitializer<?>) obj;
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return ObjectUtils.equals(getObject(), c.getObject());
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}
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/**
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* Returns a string representation for this object. This string also
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* contains a string representation of the object managed by this
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* initializer.
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*
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* @return a string for this object
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*/
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@Override
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public String toString() {
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return String.format(FMT_TO_STRING, System.identityHashCode(this),
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String.valueOf(getObject()));
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}
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}
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@ -0,0 +1,134 @@
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/*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership.
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* The ASF licenses this file to You under the Apache License, Version 2.0
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* (the "License"); you may not use this file except in compliance with
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* the License. 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 org.apache.commons.lang3.concurrent;
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import static org.junit.Assert.assertEquals;
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import static org.junit.Assert.assertTrue;
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import java.util.regex.Pattern;
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import org.junit.Before;
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import org.junit.Test;
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/**
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* Test class for {@code ConstantInitializer}.
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*
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* @author Apache Software Foundation
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* @version $Id$
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*/
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public class ConstantInitializerTest {
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/** Constant for the object managed by the initializer. */
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private static final Integer VALUE = 42;
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/** The initializer to be tested. */
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private ConstantInitializer<Integer> init;
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@Before
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public void setUp() throws Exception {
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init = new ConstantInitializer<Integer>(VALUE);
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}
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/**
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* Helper method for testing equals() and hashCode().
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*
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* @param obj the object to compare with the test instance
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* @param expected the expected result
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*/
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private void checkEquals(Object obj, boolean expected) {
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assertEquals("Wrong result of equals", expected, init.equals(obj));
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if (obj != null) {
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assertEquals("Not symmetric", expected, obj.equals(init));
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}
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if (expected) {
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assertEquals("Different hash codes", init.hashCode(),
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obj.hashCode());
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}
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}
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/**
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* Tests whether the correct object is returned.
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*/
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@Test
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public void testGetObject() {
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assertEquals("Wrong object", VALUE, init.getObject());
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}
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/**
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* Tests whether get() returns the correct object.
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*/
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@Test
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public void testGet() throws ConcurrentException {
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assertEquals("Wrong object", VALUE, init.get());
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}
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/**
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* Tests equals() if the expected result is true.
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*/
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@Test
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public void testEqualsTrue() {
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checkEquals(init, true);
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ConstantInitializer<Integer> init2 = new ConstantInitializer<Integer>(
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new Integer(VALUE.intValue()));
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checkEquals(init2, true);
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init = new ConstantInitializer<Integer>(null);
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init2 = new ConstantInitializer<Integer>(null);
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checkEquals(init2, true);
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}
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/**
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* Tests equals() if the expected result is false.
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*/
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@Test
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public void testEqualsFalse() {
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ConstantInitializer<Integer> init2 = new ConstantInitializer<Integer>(
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null);
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checkEquals(init2, false);
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init2 = new ConstantInitializer<Integer>(VALUE + 1);
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checkEquals(init2, false);
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}
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/**
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* Tests equals() with objects of other classes.
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*/
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@Test
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public void testEqualsWithOtherObjects() {
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checkEquals(null, false);
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checkEquals(this, false);
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checkEquals(new ConstantInitializer<String>("Test"), false);
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}
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/**
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* Tests the string representation.
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*/
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@Test
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public void testToString() {
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String s = init.toString();
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Pattern pattern = Pattern
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.compile("ConstantInitializer@\\d+ \\[ object = " + VALUE
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+ " \\]");
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assertTrue("Wrong string: " + s, pattern.matcher(s).matches());
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}
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/**
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* Tests the string representation if the managed object is null.
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*/
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@Test
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public void testToStringNull() {
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String s = new ConstantInitializer<Object>(null).toString();
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assertTrue("Object not found: " + s, s.indexOf("object = null") > 0);
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}
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}
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