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.iterators;
018    
019    import java.util.Iterator;
020    
021    import org.apache.commons.collections.Transformer;
022    
023    /** 
024     * Decorates an iterator such that each element returned is transformed.
025     *
026     * @since Commons Collections 1.0
027     * @version $Revision: 646777 $ $Date: 2008-04-10 13:33:15 +0100 (Thu, 10 Apr 2008) $
028     * 
029     * @author James Strachan
030     * @author Stephen Colebourne
031     */
032    public class TransformIterator implements Iterator {
033    
034        /** The iterator being used */
035        private Iterator iterator;
036        /** The transformer being used */
037        private Transformer transformer;
038    
039        //-----------------------------------------------------------------------
040        /**
041         * Constructs a new <code>TransformIterator</code> that will not function
042         * until the {@link #setIterator(Iterator) setIterator} method is 
043         * invoked.
044         */
045        public TransformIterator() {
046            super();
047        }
048    
049        /**
050         * Constructs a new <code>TransformIterator</code> that won't transform
051         * elements from the given iterator.
052         *
053         * @param iterator  the iterator to use
054         */
055        public TransformIterator(Iterator iterator) {
056            super();
057            this.iterator = iterator;
058        }
059    
060        /**
061         * Constructs a new <code>TransformIterator</code> that will use the
062         * given iterator and transformer.  If the given transformer is null,
063         * then objects will not be transformed.
064         *
065         * @param iterator  the iterator to use
066         * @param transformer  the transformer to use
067         */
068        public TransformIterator(Iterator iterator, Transformer transformer) {
069            super();
070            this.iterator = iterator;
071            this.transformer = transformer;
072        }
073    
074        //-----------------------------------------------------------------------
075        public boolean hasNext() {
076            return iterator.hasNext();
077        }
078    
079        /**
080         * Gets the next object from the iteration, transforming it using the
081         * current transformer. If the transformer is null, no transformation
082         * occurs and the object from the iterator is returned directly.
083         * 
084         * @return the next object
085         * @throws java.util.NoSuchElementException if there are no more elements
086         */
087        public Object next() {
088            return transform(iterator.next());
089        }
090    
091        public void remove() {
092            iterator.remove();
093        }
094    
095        //-----------------------------------------------------------------------
096        /** 
097         * Gets the iterator this iterator is using.
098         * 
099         * @return the iterator.
100         */
101        public Iterator getIterator() {
102            return iterator;
103        }
104    
105        /** 
106         * Sets the iterator for this iterator to use.
107         * If iteration has started, this effectively resets the iterator.
108         * 
109         * @param iterator  the iterator to use
110         */
111        public void setIterator(Iterator iterator) {
112            this.iterator = iterator;
113        }
114    
115        //-----------------------------------------------------------------------
116        /** 
117         * Gets the transformer this iterator is using.
118         * 
119         * @return the transformer.
120         */
121        public Transformer getTransformer() {
122            return transformer;
123        }
124    
125        /** 
126         * Sets the transformer this the iterator to use.
127         * A null transformer is a no-op transformer.
128         * 
129         * @param transformer  the transformer to use
130         */
131        public void setTransformer(Transformer transformer) {
132            this.transformer = transformer;
133        }
134    
135        //-----------------------------------------------------------------------
136        /**
137         * Transforms the given object using the transformer.
138         * If the transformer is null, the original object is returned as-is.
139         *
140         * @param source  the object to transform
141         * @return the transformed object
142         */
143        protected Object transform(Object source) {
144            if (transformer != null) {
145                return transformer.transform(source);
146            }
147            return source;
148        }
149    }