    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.FunctorException;
    022import org.apache.commons.collections4.Predicate;
    023import org.apache.commons.collections4.Transformer;
    024
    025/**
    026 * Predicate implementation that returns the result of a transformer.
    027 *
    028 * @since 3.0
    029 */
    030public final class TransformerPredicate<T> implements Predicate<T>, Serializable {
    031
    032    /** Serial version UID */
    033    private static final long serialVersionUID = -2407966402920578741L;
    034
    035    /** The transformer to call */
    036    private final Transformer<? super T, Boolean> iTransformer;
    037
    038    /**
    039     * Factory to create the predicate.
    040     *
    041     * @param <T> the type that the predicate queries
    042     * @param transformer  the transformer to decorate
    043     * @return the predicate
    044     * @throws NullPointerException if the transformer is null
    045     */
    046    public static <T> Predicate<T> transformerPredicate(final Transformer<? super T, Boolean> transformer) {
    047        if (transformer == null) {
    048            throw new NullPointerException("The transformer to call must not be null");
    049        }
    050        return new TransformerPredicate<>(transformer);
    051    }
    052
    053    /**
    054     * Constructor that performs no validation.
    055     * Use <code>transformerPredicate</code> if you want that.
    056     *
    057     * @param transformer  the transformer to decorate
    058     */
    059    public TransformerPredicate(final Transformer<? super T, Boolean> transformer) {
    060        super();
    061        iTransformer = transformer;
    062    }
    063
    064    /**
    065     * Evaluates the predicate returning the result of the decorated transformer.
    066     *
    067     * @param object  the input object
    068     * @return true if decorated transformer returns Boolean.TRUE
    069     * @throws FunctorException if the transformer returns an invalid type
    070     */
    071    @Override
    072    public boolean evaluate(final T object) {
    073        final Boolean result = iTransformer.transform(object);
    074        if (result == null) {
    075            throw new FunctorException(
    076                    "Transformer must return an instanceof Boolean, it was a null object");
    077        }
    078        return result.booleanValue();
    079    }
    080
    081    /**
    082     * Gets the transformer.
    083     *
    084     * @return the transformer
    085     * @since 3.1
    086     */
    087    public Transformer<? super T, Boolean> getTransformer() {
    088        return iTransformer;
    089    }
    090
    091}