    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.FunctorException;
    023import org.apache.commons.collections4.Predicate;
    024import org.apache.commons.collections4.Transformer;
    025
    026/**
    027 * Predicate implementation that returns the result of a transformer.
    028 *
    029 * @since 3.0
    030 */
    031public final class TransformerPredicate<T> implements Predicate<T>, Serializable {
    032
    033    /** Serial version UID */
    034    private static final long serialVersionUID = -2407966402920578741L;
    035
    036    /**
    037     * Factory to create the predicate.
    038     *
    039     * @param <T> the type that the predicate queries
    040     * @param transformer  the transformer to decorate
    041     * @return the predicate
    042     * @throws NullPointerException if the transformer is null
    043     */
    044    public static <T> Predicate<T> transformerPredicate(final Transformer<? super T, Boolean> transformer) {
    045        return new TransformerPredicate<>(Objects.requireNonNull(transformer, "transformer"));
    046    }
    047
    048    /** The transformer to call */
    049    private final Transformer<? super T, Boolean> iTransformer;
    050
    051    /**
    052     * Constructor that performs no validation.
    053     * Use {@code transformerPredicate} if you want that.
    054     *
    055     * @param transformer  the transformer to decorate
    056     */
    057    public TransformerPredicate(final Transformer<? super T, Boolean> transformer) {
    058        iTransformer = transformer;
    059    }
    060
    061    /**
    062     * Evaluates the predicate returning the result of the decorated transformer.
    063     *
    064     * @param object  the input object
    065     * @return true if decorated transformer returns Boolean.TRUE
    066     * @throws FunctorException if the transformer returns an invalid type
    067     */
    068    @Override
    069    public boolean evaluate(final T object) {
    070        final Boolean result = iTransformer.transform(object);
    071        if (result == null) {
    072            throw new FunctorException(
    073                    "Transformer must return an instanceof Boolean, it was a null object");
    074        }
    075        return result.booleanValue();
    076    }
    077
    078    /**
    079     * Gets the transformer.
    080     *
    081     * @return the transformer
    082     * @since 3.1
    083     */
    084    public Transformer<? super T, Boolean> getTransformer() {
    085        return iTransformer;
    086    }
    087
    088}