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.collections.set;
18
19 import java.util.Set;
20
21 import org.apache.commons.collections.Transformer;
22 import org.apache.commons.collections.collection.TransformedCollection;
23
24 /**
25 * Decorates another <code>Set</code> to transform objects that are added.
26 * <p>
27 * The add methods are affected by this class.
28 * Thus objects must be removed or searched for using their transformed form.
29 * For example, if the transformation converts Strings to Integers, you must
30 * use the Integer form to remove objects.
31 * <p>
32 * This class is Serializable from Commons Collections 3.1.
33 *
34 * @since 3.0
35 * @version $Id: TransformedSet.java 1451177 2013-02-28 11:42:31Z tn $
36 */
37 public class TransformedSet<E> extends TransformedCollection<E> implements Set<E> {
38
39 /** Serialization version */
40 private static final long serialVersionUID = 306127383500410386L;
41
42 /**
43 * Factory method to create a transforming set.
44 * <p>
45 * If there are any elements already in the set being decorated, they
46 * are NOT transformed.
47 * Contrast this with {@link #transformedSet(Set, Transformer)}.
48 *
49 * @param <E> the element type
50 * @param set the set to decorate, must not be null
51 * @param transformer the transformer to use for conversion, must not be null
52 * @return a new transformed set
53 * @throws IllegalArgumentException if set or transformer is null
54 */
55 public static <E> TransformedSet<E> transformingSet(final Set<E> set,
56 final Transformer<? super E, ? extends E> transformer) {
57 return new TransformedSet<E>(set, transformer);
58 }
59
60 /**
61 * Factory method to create a transforming set that will transform
62 * existing contents of the specified set.
63 * <p>
64 * If there are any elements already in the set being decorated, they
65 * will be transformed by this method.
66 * Contrast this with {@link #transformingSet(Set, Transformer)}.
67 *
68 * @param <E> the element type
69 * @param set the set to decorate, must not be null
70 * @param transformer the transformer to use for conversion, must not be null
71 * @return a new transformed set
72 * @throws IllegalArgumentException if set or transformer is null
73 * @since 4.0
74 */
75 public static <E> Set<E> transformedSet(final Set<E> set, final Transformer<? super E, ? extends E> transformer) {
76 final TransformedSet<E> decorated = new TransformedSet<E>(set, transformer);
77 if (transformer != null && set != null && set.size() > 0) {
78 @SuppressWarnings("unchecked") // set is type E
79 final E[] values = (E[]) set.toArray();
80 set.clear();
81 for (final E value : values) {
82 decorated.decorated().add(transformer.transform(value));
83 }
84 }
85 return decorated;
86 }
87
88 //-----------------------------------------------------------------------
89 /**
90 * Constructor that wraps (not copies).
91 * <p>
92 * If there are any elements already in the set being decorated, they
93 * are NOT transformed.
94 *
95 * @param set the set to decorate, must not be null
96 * @param transformer the transformer to use for conversion, must not be null
97 * @throws IllegalArgumentException if set or transformer is null
98 */
99 protected TransformedSet(final Set<E> set, final Transformer<? super E, ? extends E> transformer) {
100 super(set, transformer);
101 }
102
103 }