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.functor.core.collection;
018
019 import java.util.Iterator;
020
021 import org.apache.commons.functor.UnaryFunction;
022
023 /**
024 * Iterator that transforms another Iterator by applying a UnaryFunction to each returned element.
025 * @version $Revision: 1156793 $ $Date: 2011-08-11 22:06:24 +0200 (Thu, 11 Aug 2011) $
026 * @author Rodney Waldhoff
027 */
028 public final class TransformedIterator<E, T> implements Iterator<T> {
029
030 // attributes
031 // ------------------------------------------------------------------------
032
033 private final UnaryFunction<? super E, ? extends T> function;
034 private final Iterator<? extends E> iterator;
035
036 // constructor
037 // ------------------------------------------------------------------------
038 /**
039 * Create a new TransformedIterator.
040 * @param iterator Iterator to decorate
041 * @param function to apply
042 */
043 public TransformedIterator(Iterator<? extends E> iterator, UnaryFunction<? super E, ? extends T> function) {
044 if (null == iterator) {
045 throw new IllegalArgumentException("Iterator argument was null");
046 }
047 if (null == function) {
048 throw new IllegalArgumentException("filtering UnaryFunction argument was null");
049 }
050 this.function = function;
051 this.iterator = iterator;
052 }
053
054 // iterator methods
055 // ------------------------------------------------------------------------
056
057 /**
058 * {@inheritDoc}
059 * @see java.util.Iterator#hasNext()
060 */
061 public boolean hasNext() {
062 return iterator.hasNext();
063 }
064
065 /**
066 * {@inheritDoc}
067 * @see java.util.Iterator#next()
068 */
069 public T next() {
070 return function.evaluate(iterator.next());
071 }
072
073 /**
074 * {@inheritDoc}
075 * @see java.util.Iterator#remove()
076 */
077 public void remove() {
078 iterator.remove();
079 }
080
081 /**
082 * {@inheritDoc}
083 */
084 public boolean equals(Object obj) {
085 if (obj == this) {
086 return true;
087 }
088 if (!(obj instanceof TransformedIterator<?, ?>)) {
089 return false;
090 }
091 TransformedIterator<?, ?> that = (TransformedIterator<?, ?>) obj;
092 return function.equals(that.function) && iterator.equals(that.iterator);
093 }
094
095 /**
096 * {@inheritDoc}
097 */
098 public int hashCode() {
099 int hash = "TransformedIterator".hashCode();
100 hash <<= 2;
101 hash ^= function.hashCode();
102 hash <<= 2;
103 hash ^= iterator.hashCode();
104 return hash;
105 }
106
107 /**
108 * {@inheritDoc}
109 */
110 public String toString() {
111 return "TransformedIterator<" + iterator + "," + function + ">";
112 }
113
114 // class methods
115 // ------------------------------------------------------------------------
116 /**
117 * Get a Transformed Iterator instance.
118 * @param iter to decorate, if null result is null
119 * @param func transforming function, cannot be null
120 * @return Iterator<T>
121 */
122 public static <E, T> Iterator<T> transform(Iterator<? extends E> iter, UnaryFunction<? super E, ? extends T> func) {
123 if (null == iter) {
124 return null;
125 }
126 return new TransformedIterator<E, T>(iter, func);
127 }
128
129 /**
130 * Get an Iterator instance that may be transformed.
131 * @param iter to decorate, if null result is null
132 * @param func transforming function, if null result is iter
133 * @return Iterator<?>
134 */
135 public static <E> Iterator<?> maybeTransform(Iterator<? extends E> iter, UnaryFunction<? super E, ?> func) {
136 return null == func ? (null == iter ? null : iter) : new TransformedIterator<E, Object>(iter, func);
137 }
138
139 }