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.Iterator;
021    import java.util.Map;
022    
023    import org.apache.commons.collections.Closure;
024    import org.apache.commons.collections.Predicate;
025    
026    /**
027     * Closure implementation calls the closure whose predicate returns true,
028     * like a switch statement.
029     * 
030     * @since Commons Collections 3.0
031     * @version $Revision: 646777 $ $Date: 2008-04-10 13:33:15 +0100 (Thu, 10 Apr 2008) $
032     *
033     * @author Stephen Colebourne
034     */
035    public class SwitchClosure implements Closure, Serializable {
036    
037        /** Serial version UID */
038        private static final long serialVersionUID = 3518477308466486130L;
039    
040        /** The tests to consider */
041        private final Predicate[] iPredicates;
042        /** The matching closures to call */
043        private final Closure[] iClosures;
044        /** The default closure to call if no tests match */
045        private final Closure iDefault;
046    
047        /**
048         * Factory method that performs validation and copies the parameter arrays.
049         * 
050         * @param predicates  array of predicates, cloned, no nulls
051         * @param closures  matching array of closures, cloned, no nulls
052         * @param defaultClosure  the closure to use if no match, null means nop
053         * @return the <code>chained</code> closure
054         * @throws IllegalArgumentException if array is null
055         * @throws IllegalArgumentException if any element in the array is null
056         */
057        public static Closure getInstance(Predicate[] predicates, Closure[] closures, Closure defaultClosure) {
058            FunctorUtils.validate(predicates);
059            FunctorUtils.validate(closures);
060            if (predicates.length != closures.length) {
061                throw new IllegalArgumentException("The predicate and closure arrays must be the same size");
062            }
063            if (predicates.length == 0) {
064                return (defaultClosure == null ? NOPClosure.INSTANCE : defaultClosure);
065            }
066            predicates = FunctorUtils.copy(predicates);
067            closures = FunctorUtils.copy(closures);
068            return new SwitchClosure(predicates, closures, defaultClosure);
069        }
070    
071        /**
072         * Create a new Closure that calls one of the closures depending 
073         * on the predicates. 
074         * <p>
075         * The Map consists of Predicate keys and Closure values. A closure 
076         * is called if its matching predicate returns true. Each predicate is evaluated
077         * until one returns true. If no predicates evaluate to true, the default
078         * closure is called. The default closure is set in the map with a 
079         * null key. The ordering is that of the iterator() method on the entryset 
080         * collection of the map.
081         * 
082         * @param predicatesAndClosures  a map of predicates to closures
083         * @return the <code>switch</code> closure
084         * @throws IllegalArgumentException if the map is null
085         * @throws IllegalArgumentException if any closure in the map is null
086         * @throws ClassCastException  if the map elements are of the wrong type
087         */
088        public static Closure getInstance(Map predicatesAndClosures) {
089            Closure[] closures = null;
090            Predicate[] preds = null;
091            if (predicatesAndClosures == null) {
092                throw new IllegalArgumentException("The predicate and closure map must not be null");
093            }
094            if (predicatesAndClosures.size() == 0) {
095                return NOPClosure.INSTANCE;
096            }
097            // convert to array like this to guarantee iterator() ordering
098            Closure defaultClosure = (Closure) predicatesAndClosures.remove(null);
099            int size = predicatesAndClosures.size();
100            if (size == 0) {
101                return (defaultClosure == null ? NOPClosure.INSTANCE : defaultClosure);
102            }
103            closures = new Closure[size];
104            preds = new Predicate[size];
105            int i = 0;
106            for (Iterator it = predicatesAndClosures.entrySet().iterator(); it.hasNext();) {
107                Map.Entry entry = (Map.Entry) it.next();
108                preds[i] = (Predicate) entry.getKey();
109                closures[i] = (Closure) entry.getValue();
110                i++;
111            }
112            return new SwitchClosure(preds, closures, defaultClosure);
113        }
114        
115        /**
116         * Constructor that performs no validation.
117         * Use <code>getInstance</code> if you want that.
118         * 
119         * @param predicates  array of predicates, not cloned, no nulls
120         * @param closures  matching array of closures, not cloned, no nulls
121         * @param defaultClosure  the closure to use if no match, null means nop
122         */
123        public SwitchClosure(Predicate[] predicates, Closure[] closures, Closure defaultClosure) {
124            super();
125            iPredicates = predicates;
126            iClosures = closures;
127            iDefault = (defaultClosure == null ? NOPClosure.INSTANCE : defaultClosure);
128        }
129    
130        /**
131         * Executes the closure whose matching predicate returns true
132         * 
133         * @param input  the input object
134         */
135        public void execute(Object input) {
136            for (int i = 0; i < iPredicates.length; i++) {
137                if (iPredicates[i].evaluate(input) == true) {
138                    iClosures[i].execute(input);
139                    return;
140                }
141            }
142            iDefault.execute(input);
143        }
144    
145        /**
146         * Gets the predicates, do not modify the array.
147         * 
148         * @return the predicates
149         * @since Commons Collections 3.1
150         */
151        public Predicate[] getPredicates() {
152            return iPredicates;
153        }
154    
155        /**
156         * Gets the closures, do not modify the array.
157         * 
158         * @return the closures
159         * @since Commons Collections 3.1
160         */
161        public Closure[] getClosures() {
162            return iClosures;
163        }
164    
165        /**
166         * Gets the default closure.
167         * 
168         * @return the default closure
169         * @since Commons Collections 3.1
170         */
171        public Closure getDefaultClosure() {
172            return iDefault;
173        }
174        
175    }