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}