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.Predicate;
022import org.apache.commons.collections4.Transformer;
023
024/**
025 * Transformer implementation that calls a Predicate using the input object
026 * and then returns the result.
027 *
028 * @param <T> the type of the input and result to the function.
029 * @since 3.0
030 */
031public class PredicateTransformer<T> implements Transformer<T, Boolean>, Serializable {
032
033    /** Serial version UID */
034    private static final long serialVersionUID = 5278818408044349346L;
035
036    /**
037     * Factory method that performs validation.
038     *
039     * @param <T>  the input type
040     * @param predicate  the predicate to call, not null
041     * @return the {@code predicate} transformer
042     * @throws IllegalArgumentException if the predicate is null
043     */
044    public static <T> Transformer<T, Boolean> predicateTransformer(final Predicate<? super T> predicate) {
045        if (predicate == null) {
046            throw new IllegalArgumentException("Predicate must not be null");
047        }
048        return new PredicateTransformer<>(predicate);
049    }
050
051    /** The closure to wrap */
052    private final Predicate<? super T> iPredicate;
053
054    /**
055     * Constructor that performs no validation.
056     * Use {@code predicateTransformer} if you want that.
057     *
058     * @param predicate  the predicate to call, not null
059     */
060    public PredicateTransformer(final Predicate<? super T> predicate) {
061        iPredicate = predicate;
062    }
063
064    /**
065     * Gets the predicate.
066     *
067     * @return the predicate
068     * @since 3.1
069     */
070    public Predicate<? super T> getPredicate() {
071        return iPredicate;
072    }
073
074    /**
075     * Transforms the input to result by calling a predicate.
076     *
077     * @param input  the input object to transform
078     * @return the transformed result
079     */
080    @Override
081    public Boolean transform(final T input) {
082        return Boolean.valueOf(iPredicate.test(input));
083    }
084
085}