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 * @version $Id: TransformerPredicate.html 972421 2015-11-14 20:00:04Z tn $
030 */
031public final class TransformerPredicate<T> implements Predicate<T>, Serializable {
032
033    /** Serial version UID */
034    private static final long serialVersionUID = -2407966402920578741L;
035
036    /** The transformer to call */
037    private final Transformer<? super T, Boolean> iTransformer;
038
039    /**
040     * Factory to create the predicate.
041     *
042     * @param <T> the type that the predicate queries
043     * @param transformer  the transformer to decorate
044     * @return the predicate
045     * @throws IllegalArgumentException if the transformer is null
046     */
047    public static <T> Predicate<T> transformerPredicate(final Transformer<? super T, Boolean> transformer) {
048        if (transformer == null) {
049            throw new IllegalArgumentException("The transformer to call must not be null");
050        }
051        return new TransformerPredicate<T>(transformer);
052    }
053
054    /**
055     * Constructor that performs no validation.
056     * Use <code>transformerPredicate</code> if you want that.
057     *
058     * @param transformer  the transformer to decorate
059     */
060    public TransformerPredicate(final Transformer<? super T, Boolean> transformer) {
061        super();
062        iTransformer = transformer;
063    }
064
065    /**
066     * Evaluates the predicate returning the result of the decorated transformer.
067     *
068     * @param object  the input object
069     * @return true if decorated transformer returns Boolean.TRUE
070     * @throws FunctorException if the transformer returns an invalid type
071     */
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}