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}