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 *  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,
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package org.apache.commons.collections.functors;

import java.io.Serializable;

import org.apache.commons.collections.Transformer;

Transformer implementation that returns the same constant each time.

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:
Stephen Colebourne
Since:
Commons Collections 3.0
Version:
$Revision: 646777 $ $Date: 2008-04-10 14:33:15 +0200 (Thu, 10 Apr 2008) $/**
 * 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.
 * 
 * @since Commons Collections 3.0
 * @version $Revision: 646777 $ $Date: 2008-04-10 14:33:15 +0200 (Thu, 10 Apr 2008) $
 *
 * @author Stephen Colebourne
 */
public class ConstantTransformer implements Transformer, Serializable {

    
Serial version UID /** Serial version UID */
    private static final long serialVersionUID = 6374440726369055124L;
    
    
Returns null each time /** Returns null each time */
    public static final Transformer NULL_INSTANCE = new ConstantTransformer(null);

    
The closures to call in turn /** The closures to call in turn */
    private final Object iConstant;

    
Transformer method that performs validation.
Params:
constantToReturn –  the constant object to return each time in the factory
Returns:
the constant factory./**
     * 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 Transformer getInstance(Object constantToReturn) {
        if (constantToReturn == null) {
            return NULL_INSTANCE;
        }
        return new ConstantTransformer(constantToReturn);
    }
    
    
Constructor that performs no validation.
Use getInstance if you want that.
Params:
constantToReturn –  the constant to return each time/**
     * Constructor that performs no validation.
     * Use <code>getInstance</code> if you want that.
     * 
     * @param constantToReturn  the constant to return each time
     */
    public ConstantTransformer(Object constantToReturn) {
        super();
        iConstant = constantToReturn;
    }

    
Transforms the input by ignoring it and returning the stored constant instead.
Params:
input –  the input object which is ignored
Returns:
the stored constant/**
     * Transforms the input by ignoring it and returning the stored constant instead.
     * 
     * @param input  the input object which is ignored
     * @return the stored constant
     */
    public Object transform(Object input) {
        return iConstant;
    }

    
Gets the constant.
Returns:
the constant
Since:
Commons Collections 3.1/**
     * Gets the constant.
     * 
     * @return the constant
     * @since Commons Collections 3.1
     */
    public Object getConstant() {
        return iConstant;
    }

}