    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;
    020import java.util.Objects;
    021
    022import org.apache.commons.collections4.Factory;
    023import org.apache.commons.collections4.Transformer;
    024
    025/**
    026 * Transformer implementation that calls a Factory and returns the result.
    027 *
    028 * @param <T> the type of the input to the function.
    029 * @param <R> the type of the result of the function.
    030 * @since 3.0
    031 */
    032public class FactoryTransformer<T, R> implements Transformer<T, R>, Serializable {
    033
    034    /** Serial version UID */
    035    private static final long serialVersionUID = -6817674502475353160L;
    036
    037    /**
    038     * Factory method that performs validation.
    039     *
    040     * @param <I>  the input type
    041     * @param <O>  the output type
    042     * @param factory  the factory to call, not null
    043     * @return the {@code factory} transformer
    044     * @throws NullPointerException if the factory is null
    045     */
    046    public static <I, O> Transformer<I, O> factoryTransformer(final Factory<? extends O> factory) {
    047        return new FactoryTransformer<>(Objects.requireNonNull(factory, "factory"));
    048    }
    049
    050    /** The factory to wrap */
    051    private final Factory<? extends R> iFactory;
    052
    053    /**
    054     * Constructor that performs no validation.
    055     * Use {@code factoryTransformer} if you want that.
    056     *
    057     * @param factory  the factory to call, not null
    058     */
    059    public FactoryTransformer(final Factory<? extends R> factory) {
    060        iFactory = factory;
    061    }
    062
    063    /**
    064     * Gets the factory.
    065     *
    066     * @return the factory
    067     * @since 3.1
    068     */
    069    public Factory<? extends R> getFactory() {
    070        return iFactory;
    071    }
    072
    073    /**
    074     * Transforms the input by ignoring the input and returning the result of
    075     * calling the decorated factory.
    076     *
    077     * @param input  the input object to transform
    078     * @return the transformed result
    079     */
    080    @Override
    081    public R transform(final T input) {
    082        return iFactory.get();
    083    }
    084
    085}