// GenericsNote: Converted.
/*
* Copyright 2001-2004 The Apache Software Foundation
*
* 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 org.apache.commons.collections15.functors;
import java.io.Serializable;
import org.apache.commons.collections15.Transformer;
/**
* Transformer implementation that returns the same constant each time.
* <p/>
* No check is made that the object is immutable. In general, only immutable
* objects should use the constant factory. Mutable objects should use the
* prototype factory.
*
* @author Matt Hall, John Watkinson, Stephen Colebourne
* @version $Revision: 1.1 $ $Date: 2005/10/11 17:05:24 $
* @since Commons Collections 3.0
*/
public class ConstantTransformer<T>
implements Transformer<Object, T>, Serializable {
/**
* Serial version UID
*/
static final long serialVersionUID = 6374440726369055124L;
/**
* Returns null each time
*/
public static final Transformer NULL_INSTANCE = new ConstantTransformer(
null);
/**
* The closures to call in turn
*/
private final T iConstant;
/**
* Transformer method that performs validation.
*
* @param constantToReturn
* the constant object to return each time in the factory
* @return the <code>constant</code> factory.
*/
public static <T> Transformer<Object, T> getInstance(T constantToReturn) {
if (constantToReturn == null) {
return NULL_INSTANCE;
}
return new ConstantTransformer<T>(constantToReturn);
}
/**
* Constructor that performs no validation. Use <code>getInstance</code> if
* you want that.
*
* @param constantToReturn
* the constant to return each time
*/
public ConstantTransformer(T constantToReturn) {
super();
iConstant = constantToReturn;
}
/**
* Transforms the input by ignoring it and returning the stored constant
* instead.
*
* @param input
* the input object which is ignored
* @return the stored constant
*/
@Override
public T transform(Object input) {
return iConstant;
}
/**
* Gets the constant.
*
* @return the constant
* @since Commons Collections 3.1
*/
public T getConstant() {
return iConstant;
}
}