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/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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 org.apache.commons.lang3.concurrent;
import java.util.Objects;
/**
*
* A very simple implementation of the {@link ConcurrentInitializer} interface
* which always returns the same object.
*
*
* An instance of this class is passed a reference to an object when it is
* constructed. The {@link #get()} method just returns this object. No
* synchronization is required.
*
*
* This class is useful for instance for unit testing or in cases where a
* specific object has to be passed to an object which expects a
* {@link ConcurrentInitializer}.
*
*
* @since 3.0
* @param the type of the object managed by this initializer
*/
public class ConstantInitializer implements ConcurrentInitializer {
/** Constant for the format of the string representation. */
private static final String FMT_TO_STRING = "ConstantInitializer@%d [ object = %s ]";
/** Stores the managed object. */
private final T object;
/**
* Creates a new instance of {@code ConstantInitializer} and initializes it
* with the object to be managed. The {@code get()} method will always
* return the object passed here. This class does not place any restrictions
* on the object. It may be null, then {@code get()} will return
* null, too.
*
* @param obj the object to be managed by this initializer
*/
public ConstantInitializer(final T obj) {
object = obj;
}
/**
* Directly returns the object that was passed to the constructor. This is
* the same object as returned by {@code get()}. However, this method does
* not declare that it throws an exception.
*
* @return the object managed by this initializer
*/
public final T getObject() {
return object;
}
/**
* Returns the object managed by this initializer. This implementation just
* returns the object passed to the constructor.
*
* @return the object managed by this initializer
* @throws ConcurrentException if an error occurs
*/
@Override
public T get() throws ConcurrentException {
return getObject();
}
/**
* Returns a hash code for this object. This implementation returns the hash
* code of the managed object.
*
* @return a hash code for this object
*/
@Override
public int hashCode() {
return getObject() != null ? getObject().hashCode() : 0;
}
/**
* Compares this object with another one. This implementation returns
* true if and only if the passed in object is an instance of
* {@code ConstantInitializer} which refers to an object equals to the
* object managed by this instance.
*
* @param obj the object to compare to
* @return a flag whether the objects are equal
*/
@Override
public boolean equals(final Object obj) {
if (this == obj) {
return true;
}
if (!(obj instanceof ConstantInitializer)) {
return false;
}
final ConstantInitializer c = (ConstantInitializer) obj;
return Objects.equals(getObject(), c.getObject());
}
/**
* Returns a string representation for this object. This string also
* contains a string representation of the object managed by this
* initializer.
*
* @return a string for this object
*/
@Override
public String toString() {
return String.format(FMT_TO_STRING, Integer.valueOf(System.identityHashCode(this)),
String.valueOf(getObject()));
}
}