    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.Factory;
    022import org.apache.commons.collections4.Transformer;
    023
    024/**
    025 * Transformer implementation that calls a Factory and returns the result.
    026 *
    027 * @since 3.0
    028 */
    029public class FactoryTransformer<I, O> implements Transformer<I, O>, Serializable {
    030
    031    /** Serial version UID */
    032    private static final long serialVersionUID = -6817674502475353160L;
    033
    034    /** The factory to wrap */
    035    private final Factory<? extends O> iFactory;
    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</code> 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        if (factory == null) {
    048            throw new NullPointerException("Factory must not be null");
    049        }
    050        return new FactoryTransformer<>(factory);
    051    }
    052
    053    /**
    054     * Constructor that performs no validation.
    055     * Use <code>factoryTransformer</code> if you want that.
    056     *
    057     * @param factory  the factory to call, not null
    058     */
    059    public FactoryTransformer(final Factory<? extends O> factory) {
    060        super();
    061        iFactory = factory;
    062    }
    063
    064    /**
    065     * Transforms the input by ignoring the input and returning the result of
    066     * calling the decorated factory.
    067     *
    068     * @param input  the input object to transform
    069     * @return the transformed result
    070     */
    071    @Override
    072    public O transform(final I input) {
    073        return iFactory.create();
    074    }
    075
    076    /**
    077     * Gets the factory.
    078     *
    079     * @return the factory
    080     * @since 3.1
    081     */
    082    public Factory<? extends O> getFactory() {
    083        return iFactory;
    084    }
    085
    086}