001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.commons.collections4.functors;
018
019import java.io.Serializable;
020
021import org.apache.commons.collections4.Transformer;
022
023/**
024 * Transformer implementation that returns the result of calling
025 * <code>String.valueOf</code> on the input object.
026 *
027 * @since 3.0
028 * @version $Id: StringValueTransformer.html 887892 2013-11-24 13:43:45Z tn $
029 */
030public final class StringValueTransformer<T> implements Transformer<T, String>, Serializable {
031
032    /** Serial version UID */
033    private static final long serialVersionUID = 7511110693171758606L;
034
035    /** Singleton predicate instance */
036    private static final Transformer<Object, String> INSTANCE = new StringValueTransformer<Object>();
037
038    /**
039     * Factory returning the singleton instance.
040     *
041     * @param <T>  the input type
042     * @return the singleton instance
043     * @since 3.1
044     */
045    @SuppressWarnings("unchecked")
046    public static <T> Transformer<T, String> stringValueTransformer() {
047        return (Transformer<T, String>) INSTANCE;
048    }
049
050    /**
051     * Restricted constructor.
052     */
053    private StringValueTransformer() {
054        super();
055    }
056
057    /**
058     * Transforms the input to result by calling <code>String.valueOf</code>.
059     *
060     * @param input  the input object to transform
061     * @return the transformed result
062     */
063    public String transform(final T input) {
064        return String.valueOf(input);
065    }
066
067    private Object readResolve() {
068        return INSTANCE;
069    }
070
071}