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.bag;
18
19 import java.util.Set;
20
21 import org.apache.commons.collections4.Bag;
22 import org.apache.commons.collections4.Transformer;
23 import org.apache.commons.collections4.collection.TransformedCollection;
24 import org.apache.commons.collections4.set.TransformedSet;
25
26 /**
27 * Decorates another {@link Bag} to transform objects that are added.
28 * <p>
29 * The add methods are affected by this class.
30 * Thus objects must be removed or searched for using their transformed form.
31 * For example, if the transformation converts Strings to Integers, you must
32 * use the Integer form to remove objects.
33 * </p>
34 * <p>
35 * This class is Serializable from Commons Collections 3.1.
36 * </p>
37 *
38 * @param <E> the type of elements in this bag
39 * @since 3.0
40 */
41 public class TransformedBag<E> extends TransformedCollection<E> implements Bag<E> {
42
43 /** Serialization version */
44 private static final long serialVersionUID = 5421170911299074185L;
45
46 /**
47 * Factory method to create a transforming bag that will transform
48 * existing contents of the specified bag.
49 * <p>
50 * If there are any elements already in the bag being decorated, they
51 * will be transformed by this method.
52 * Contrast this with {@link #transformingBag(Bag, Transformer)}.
53 *
54 * @param <E> the type of the elements in the bag
55 * @param bag the bag to decorate, must not be null
56 * @param transformer the transformer to use for conversion, must not be null
57 * @return a new transformed Bag
58 * @throws NullPointerException if bag or transformer is null
59 * @since 4.0
60 */
61 public static <E> Bag<E> transformedBag(final Bag<E> bag, final Transformer<? super E, ? extends E> transformer) {
62 final TransformedBag<E> decorated = new TransformedBag<>(bag, transformer);
63 if (!bag.isEmpty()) {
64 @SuppressWarnings("unchecked") // Bag is of type E
65 final E[] values = (E[]) bag.toArray(); // NOPMD - false positive for generics
66 bag.clear();
67 for (final E value : values) {
68 decorated.decorated().add(transformer.transform(value));
69 }
70 }
71 return decorated;
72 }
73
74 /**
75 * Factory method to create a transforming bag.
76 * <p>
77 * If there are any elements already in the bag being decorated, they
78 * are NOT transformed. Contrast this with {@link #transformedBag(Bag, Transformer)}.
79 *
80 * @param <E> the type of the elements in the bag
81 * @param bag the bag to decorate, must not be null
82 * @param transformer the transformer to use for conversion, must not be null
83 * @return a new transformed Bag
84 * @throws NullPointerException if bag or transformer is null
85 * @since 4.0
86 */
87 public static <E> Bag<E> transformingBag(final Bag<E> bag, final Transformer<? super E, ? extends E> transformer) {
88 return new TransformedBag<>(bag, transformer);
89 }
90
91 /**
92 * Constructor that wraps (not copies).
93 * <p>
94 * If there are any elements already in the bag being decorated, they
95 * are NOT transformed.
96 *
97 * @param bag the bag to decorate, must not be null
98 * @param transformer the transformer to use for conversion, must not be null
99 * @throws NullPointerException if bag or transformer is null
100 */
101 protected TransformedBag(final Bag<E> bag, final Transformer<? super E, ? extends E> transformer) {
102 super(bag, transformer);
103 }
104
105 @Override
106 public boolean add(final E object, final int nCopies) {
107 return getBag().add(transform(object), nCopies);
108 }
109
110 @Override
111 public boolean equals(final Object object) {
112 return object == this || decorated().equals(object);
113 }
114
115 /**
116 * Gets the decorated bag.
117 *
118 * @return the decorated bag
119 */
120 protected Bag<E> getBag() {
121 return (Bag<E>) decorated();
122 }
123
124 @Override
125 public int getCount(final Object object) {
126 return getBag().getCount(object);
127 }
128
129 @Override
130 public int hashCode() {
131 return decorated().hashCode();
132 }
133
134 @Override
135 public boolean remove(final Object object, final int nCopies) {
136 return getBag().remove(object, nCopies);
137 }
138
139 @Override
140 public Set<E> uniqueSet() {
141 final Set<E> set = getBag().uniqueSet();
142 return TransformedSet.<E>transformingSet(set, transformer);
143 }
144
145 }