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} on the input object.
026 *
027 * @since 3.0
028 */
029public final class StringValueTransformer<T> implements Transformer<T, String>, Serializable {
030
031    /** Serial version UID */
032    private static final long serialVersionUID = 7511110693171758606L;
033
034    /** Singleton predicate instance */
035    private static final Transformer<Object, String> INSTANCE = new StringValueTransformer<>();
036
037    /**
038     * Factory returning the singleton instance.
039     *
040     * @param <T>  the input type
041     * @return the singleton instance
042     * @since 3.1
043     */
044    @SuppressWarnings("unchecked")
045    public static <T> Transformer<T, String> stringValueTransformer() {
046        return (Transformer<T, String>) INSTANCE;
047    }
048
049    /**
050     * Restricted constructor.
051     */
052    private StringValueTransformer() {
053    }
054
055    private Object readResolve() {
056        return INSTANCE;
057    }
058
059    /**
060     * Transforms the input to result by calling {@code String.valueOf}.
061     *
062     * @param input  the input object to transform
063     * @return the transformed result
064     */
065    @Override
066    public String transform(final T input) {
067        return String.valueOf(input);
068    }
069
070}