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 }