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     */
017    package org.apache.commons.collections.functors;
018    
019    import java.io.Serializable;
020    
021    import org.apache.commons.collections.Predicate;
022    import org.apache.commons.collections.Transformer;
023    
024    /**
025     * Predicate implementation that transforms the given object before invoking
026     * another <code>Predicate</code>.
027     * 
028     * @since Commons Collections 3.1
029     * @version $Revision: 646777 $ $Date: 2008-04-10 13:33:15 +0100 (Thu, 10 Apr 2008) $
030     * @author Alban Peignier
031     * @author Stephen Colebourne
032     */
033    public final class TransformedPredicate implements Predicate, PredicateDecorator, Serializable {
034    
035        /** Serial version UID */
036        private static final long serialVersionUID = -5596090919668315834L;
037        
038        /** The transformer to call */
039        private final Transformer iTransformer;
040        /** The predicate to call */
041        private final Predicate iPredicate;
042    
043        /**
044         * Factory to create the predicate.
045         * 
046         * @param transformer  the transformer to call
047         * @param predicate  the predicate to call with the result of the transform
048         * @return the predicate
049         * @throws IllegalArgumentException if the transformer or the predicate is null
050         */
051        public static Predicate getInstance(Transformer transformer, Predicate predicate) {
052            if (transformer == null) {
053                throw new IllegalArgumentException("The transformer to call must not be null");
054            }
055            if (predicate == null) {
056                throw new IllegalArgumentException("The predicate to call must not be null");
057            }
058            return new TransformedPredicate(transformer, predicate);
059        }
060    
061        /**
062         * Constructor that performs no validation.
063         * Use <code>getInstance</code> if you want that.
064         * 
065         * @param transformer  the transformer to use
066         * @param predicate  the predicate to decorate
067         */
068        public TransformedPredicate(Transformer transformer, Predicate predicate) {
069            iTransformer = transformer;
070            iPredicate = predicate;
071        }
072        
073        /**
074         * Evaluates the predicate returning the result of the decorated predicate
075         * once the input has been transformed
076         * 
077         * @param object  the input object which will be transformed
078         * @return true if decorated predicate returns true
079         */
080        public boolean evaluate(Object object) {
081            Object result = iTransformer.transform(object);
082            return iPredicate.evaluate(result);
083        }
084    
085        /**
086         * Gets the predicate being decorated.
087         * 
088         * @return the predicate as the only element in an array
089         * @since Commons Collections 3.1
090         */
091        public Predicate[] getPredicates() {
092            return new Predicate[] {iPredicate};
093        }
094    
095        /**
096         * Gets the transformer in use.
097         * 
098         * @return the transformer
099         */
100        public Transformer getTransformer() {
101            return iTransformer;
102        }
103    
104    }