FactoryTransformer.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.commons.collections4.functors;

import java.io.Serializable;
import java.util.Objects;

import org.apache.commons.collections4.Factory;
import org.apache.commons.collections4.Transformer;

/**
 * Transformer implementation that calls a Factory and returns the result.
 *
 * @param <T> the type of the input to the function.
 * @param <R> the type of the result of the function.
 * @since 3.0
 */
public class FactoryTransformer<T, R> implements Transformer<T, R>, Serializable {

    /** Serial version UID */
    private static final long serialVersionUID = -6817674502475353160L;

    /**
     * Factory method that performs validation.
     *
     * @param <I>  the input type
     * @param <O>  the output type
     * @param factory  the factory to call, not null
     * @return the {@code factory} transformer
     * @throws NullPointerException if the factory is null
     */
    public static <I, O> Transformer<I, O> factoryTransformer(final Factory<? extends O> factory) {
        return new FactoryTransformer<>(Objects.requireNonNull(factory, "factory"));
    }

    /** The factory to wrap */
    private final Factory<? extends R> iFactory;

    /**
     * Constructor that performs no validation.
     * Use {@code factoryTransformer} if you want that.
     *
     * @param factory  the factory to call, not null
     */
    public FactoryTransformer(final Factory<? extends R> factory) {
        iFactory = factory;
    }

    /**
     * Gets the factory.
     *
     * @return the factory
     * @since 3.1
     */
    public Factory<? extends R> getFactory() {
        return iFactory;
    }

    /**
     * Transforms the input by ignoring the input and returning the result of
     * calling the decorated factory.
     *
     * @param input  the input object to transform
     * @return the transformed result
     */
    @Override
    public R transform(final T input) {
        return iFactory.get();
    }

}