1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17 package org.apache.commons.collections4.iterators;
18
19 import java.util.Iterator;
20
21 import org.apache.commons.collections4.Transformer;
22
23 /**
24 * Decorates an iterator such that each element returned is transformed.
25 *
26 * @since 1.0
27 */
28 public class TransformIterator<I, O> implements Iterator<O> {
29
30 /** The iterator being used */
31 private Iterator<? extends I> iterator;
32 /** The transformer being used */
33 private Transformer<? super I, ? extends O> transformer;
34
35 /**
36 * Constructs a new {@code TransformIterator} that will not function
37 * until the {@link #setIterator(Iterator) setIterator} and
38 * {@link #setTransformer(Transformer)} methods are invoked.
39 */
40 public TransformIterator() {
41 }
42
43 /**
44 * Constructs a new {@code TransformIterator} that won't transform
45 * elements from the given iterator.
46 *
47 * @param iterator the iterator to use
48 */
49 public TransformIterator(final Iterator<? extends I> iterator) {
50 this.iterator = iterator;
51 }
52
53 /**
54 * Constructs a new {@code TransformIterator} that will use the
55 * given iterator and transformer. If the given transformer is null,
56 * then objects will not be transformed.
57 *
58 * @param iterator the iterator to use
59 * @param transformer the transformer to use
60 */
61 public TransformIterator(final Iterator<? extends I> iterator,
62 final Transformer<? super I, ? extends O> transformer) {
63 this.iterator = iterator;
64 this.transformer = transformer;
65 }
66
67 /**
68 * Gets the iterator this iterator is using.
69 *
70 * @return the iterator.
71 */
72 public Iterator<? extends I> getIterator() {
73 return iterator;
74 }
75
76 /**
77 * Gets the transformer this iterator is using.
78 *
79 * @return the transformer.
80 */
81 public Transformer<? super I, ? extends O> getTransformer() {
82 return transformer;
83 }
84
85 @Override
86 public boolean hasNext() {
87 return iterator.hasNext();
88 }
89
90 /**
91 * Gets the next object from the iteration, transforming it using the
92 * current transformer. If the transformer is null, no transformation
93 * occurs and the object from the iterator is returned directly.
94 *
95 * @return the next object
96 * @throws java.util.NoSuchElementException if there are no more elements
97 */
98 @Override
99 public O next() {
100 return transform(iterator.next());
101 }
102
103 @Override
104 public void remove() {
105 iterator.remove();
106 }
107
108 /**
109 * Sets the iterator for this iterator to use.
110 * If iteration has started, this effectively resets the iterator.
111 *
112 * @param iterator the iterator to use
113 */
114 public void setIterator(final Iterator<? extends I> iterator) {
115 this.iterator = iterator;
116 }
117
118 /**
119 * Sets the transformer this the iterator to use.
120 * A null transformer is a no-op transformer.
121 *
122 * @param transformer the transformer to use
123 */
124 public void setTransformer(final Transformer<? super I, ? extends O> transformer) {
125 this.transformer = transformer;
126 }
127
128 /**
129 * Transforms the given object using the transformer.
130 * If the transformer is null, the original object is returned as-is.
131 *
132 * @param source the object to transform
133 * @return the transformed object
134 */
135 protected O transform(final I source) {
136 return transformer.transform(source);
137 }
138 }