    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}