    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.Predicate;
    023import org.apache.commons.collections4.Transformer;
    024
    025/**
    026 * Transformer implementation that will call one of two closures based on whether a predicate evaluates
    027 * as true or false.
    028 *
    029 * @param <I> The input type for the transformer
    030 * @param <O> The output type for the transformer
    031 *
    032 * @since 4.1
    033 */
    034public class IfTransformer<I, O> implements Transformer<I, O>, Serializable {
    035
    036    /** Serial version UID */
    037    private static final long serialVersionUID = 8069309411242014252L;
    038
    039    /**
    040     * Factory method that performs validation.
    041     *
    042     * @param <I>  input type for the transformer
    043     * @param <O>  output type for the transformer
    044     * @param predicate  predicate to switch on
    045     * @param trueTransformer  transformer used if true
    046     * @param falseTransformer  transformer used if false
    047     * @return the {@code if} transformer
    048     * @throws NullPointerException if either argument is null
    049     */
    050    public static <I, O> Transformer<I, O> ifTransformer(final Predicate<? super I> predicate,
    051                                                         final Transformer<? super I, ? extends O> trueTransformer,
    052                                                         final Transformer<? super I, ? extends O> falseTransformer) {
    053        return new IfTransformer<>(Objects.requireNonNull(predicate, "predicate"),
    054                Objects.requireNonNull(trueTransformer, "trueTransformer"),
    055                Objects.requireNonNull(falseTransformer, "falseTransformer"));
    056    }
    057    /**
    058     * Factory method that performs validation.
    059     * <p>
    060     * This factory creates a transformer that just returns the input object when
    061     * the predicate is false.
    062     *
    063     * @param <T>  input and output type for the transformer
    064     * @param predicate  predicate to switch on
    065     * @param trueTransformer  transformer used if true
    066     * @return the {@code if} transformer
    067     * @throws NullPointerException if either argument is null
    068     */
    069    public static <T> Transformer<T, T> ifTransformer(
    070            final Predicate<? super T> predicate,
    071            final Transformer<? super T, ? extends T> trueTransformer) {
    072        return new IfTransformer<>(Objects.requireNonNull(predicate, "predicate"),
    073                Objects.requireNonNull(trueTransformer, "trueTransformer"), NOPTransformer.<T>nopTransformer());
    074    }
    075    /** The test */
    076    private final Predicate<? super I> iPredicate;
    077
    078    /** The transformer to use if true */
    079    private final Transformer<? super I, ? extends O> iTrueTransformer;
    080
    081    /** The transformer to use if false */
    082    private final Transformer<? super I, ? extends O> iFalseTransformer;
    083
    084    /**
    085     * Constructor that performs no validation.
    086     * Use the static factory method {@code ifTransformer} if you want that.
    087     *
    088     * @param predicate  predicate to switch on, not null
    089     * @param trueTransformer  transformer used if true, not null
    090     * @param falseTransformer  transformer used if false, not null
    091     */
    092    public IfTransformer(final Predicate<? super I> predicate,
    093        final Transformer<? super I, ? extends O> trueTransformer,
    094        final Transformer<? super I, ? extends O> falseTransformer) {
    095
    096        iPredicate = predicate;
    097        iTrueTransformer = trueTransformer;
    098        iFalseTransformer = falseTransformer;
    099    }
    100
    101    /**
    102     * Gets the transformer used when false.
    103     *
    104     * @return the transformer
    105     */
    106    public Transformer<? super I, ? extends O> getFalseTransformer() {
    107        return iFalseTransformer;
    108    }
    109
    110    /**
    111     * Gets the predicate.
    112     *
    113     * @return the predicate
    114     */
    115    public Predicate<? super I> getPredicate() {
    116        return iPredicate;
    117    }
    118
    119    /**
    120     * Gets the transformer used when true.
    121     *
    122     * @return the transformer
    123     */
    124    public Transformer<? super I, ? extends O> getTrueTransformer() {
    125        return iTrueTransformer;
    126    }
    127
    128    /**
    129     * Transforms the input using the true or false transformer based to the result of the predicate.
    130     *
    131     * @param input  the input object to transform
    132     * @return the transformed result
    133     */
    134    @Override
    135    public O transform(final I input) {
    136        if (iPredicate.evaluate(input)) {
    137            return iTrueTransformer.transform(input);
    138        }
    139        return iFalseTransformer.transform(input);
    140    }
    141}