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    import java.util.Collection;
021    
022    import org.apache.commons.collections.Predicate;
023    
024    /**
025     * Predicate implementation that returns true if only one of the
026     * predicates return true.
027     * If the array of predicates is empty, then this predicate returns false.
028     * <p>
029     * NOTE: In versions prior to 3.2 an array size of zero or one
030     * threw an exception.
031     *
032     * @since Commons Collections 3.0
033     * @version $Revision: 646777 $ $Date: 2008-04-10 13:33:15 +0100 (Thu, 10 Apr 2008) $
034     *
035     * @author Stephen Colebourne
036     * @author Matt Benson
037     */
038    public final class OnePredicate implements Predicate, PredicateDecorator, Serializable {
039    
040        /** Serial version UID */
041        private static final long serialVersionUID = -8125389089924745785L;
042        
043        /** The array of predicates to call */
044        private final Predicate[] iPredicates;
045        
046        /**
047         * Factory to create the predicate.
048         * <p>
049         * If the array is size zero, the predicate always returns false.
050         * If the array is size one, then that predicate is returned.
051         *
052         * @param predicates  the predicates to check, cloned, not null
053         * @return the <code>any</code> predicate
054         * @throws IllegalArgumentException if the predicates array is null
055         * @throws IllegalArgumentException if any predicate in the array is null
056         */
057        public static Predicate getInstance(Predicate[] predicates) {
058            FunctorUtils.validate(predicates);
059            if (predicates.length == 0) {
060                return FalsePredicate.INSTANCE;
061            }
062            if (predicates.length == 1) {
063                return predicates[0];
064            }
065            predicates = FunctorUtils.copy(predicates);
066            return new OnePredicate(predicates);
067        }
068    
069        /**
070         * Factory to create the predicate.
071         *
072         * @param predicates  the predicates to check, cloned, not null
073         * @return the <code>one</code> predicate
074         * @throws IllegalArgumentException if the predicates array is null
075         * @throws IllegalArgumentException if any predicate in the array is null
076         */
077        public static Predicate getInstance(Collection predicates) {
078            Predicate[] preds = FunctorUtils.validate(predicates);
079            return new OnePredicate(preds);
080        }
081    
082        /**
083         * Constructor that performs no validation.
084         * Use <code>getInstance</code> if you want that.
085         * 
086         * @param predicates  the predicates to check, not cloned, not null
087         */
088        public OnePredicate(Predicate[] predicates) {
089            super();
090            iPredicates = predicates;
091        }
092    
093        /**
094         * Evaluates the predicate returning true if only one decorated predicate
095         * returns true.
096         * 
097         * @param object  the input object
098         * @return true if only one decorated predicate returns true
099         */
100        public boolean evaluate(Object object) {
101            boolean match = false;
102            for (int i = 0; i < iPredicates.length; i++) {
103                if (iPredicates[i].evaluate(object)) {
104                    if (match) {
105                        return false;
106                    }
107                    match = true;
108                }
109            }
110            return match;
111        }
112    
113        /**
114         * Gets the predicates, do not modify the array.
115         * 
116         * @return the predicates
117         * @since Commons Collections 3.1
118         */
119        public Predicate[] getPredicates() {
120            return iPredicates;
121        }
122    
123    }