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.io.IOException;
20 import java.io.ObjectInputStream;
21 import java.io.ObjectOutputStream;
22 import java.util.Collection;
23 import java.util.Iterator;
24
25 import org.apache.commons.collections4.Bag;
26
27 /**
28 * Decorates another {@link Bag} to comply with the Collection contract.
29 * <p>
30 * By decorating an existing {@link Bag} instance with a {@link CollectionBag},
31 * it can be safely passed on to methods that require Collection types that
32 * are fully compliant with the Collection contract.
33 * </p>
34 * <p>
35 * The method javadoc highlights the differences compared to the original Bag interface.
36 * </p>
37 *
38 * @see Bag
39 * @param <E> the type of elements in this bag
40 * @since 4.0
41 */
42 public final class CollectionBag<E> extends AbstractBagDecorator<E> {
43
44 /** Serialization version */
45 private static final long serialVersionUID = -2560033712679053143L;
46
47 /**
48 * Factory method to create a bag that complies to the Collection contract.
49 *
50 * @param <E> the type of the elements in the bag
51 * @param bag the bag to decorate, must not be null
52 * @return a Bag that complies to the Collection contract
53 * @throws NullPointerException if bag is null
54 */
55 public static <E> Bag<E> collectionBag(final Bag<E> bag) {
56 return new CollectionBag<>(bag);
57 }
58
59 //-----------------------------------------------------------------------
60 /**
61 * Constructor that wraps (not copies).
62 *
63 * @param bag the bag to decorate, must not be null
64 * @throws NullPointerException if bag is null
65 */
66 public CollectionBag(final Bag<E> bag) {
67 super(bag);
68 }
69
70 //-----------------------------------------------------------------------
71 /**
72 * Write the collection out using a custom routine.
73 *
74 * @param out the output stream
75 * @throws IOException if an error occurs while writing to the stream
76 */
77 private void writeObject(final ObjectOutputStream out) throws IOException {
78 out.defaultWriteObject();
79 out.writeObject(decorated());
80 }
81
82 /**
83 * Read the collection in using a custom routine.
84 *
85 * @param in the input stream
86 * @throws IOException if an error occurs while reading from the stream
87 * @throws ClassNotFoundException if an object read from the stream can not be loaded
88 * @throws ClassCastException if deserialised object has wrong type
89 */
90 @SuppressWarnings("unchecked") // will throw CCE, see Javadoc
91 private void readObject(final ObjectInputStream in) throws IOException, ClassNotFoundException {
92 in.defaultReadObject();
93 setCollection((Collection<E>) in.readObject());
94 }
95
96 //-----------------------------------------------------------------------
97 // Collection interface
98 //-----------------------------------------------------------------------
99
100 /**
101 * <i>(Change)</i>
102 * Returns <code>true</code> if the bag contains all elements in
103 * the given collection, <b>not</b> respecting cardinality. That is,
104 * if the given collection <code>coll</code> contains at least one of
105 * every object contained in this object.
106 *
107 * @param coll the collection to check against
108 * @return <code>true</code> if the Bag contains at least one of every object in the collection
109 */
110 @Override
111 public boolean containsAll(final Collection<?> coll) {
112 final Iterator<?> e = coll.iterator();
113 while (e.hasNext()) {
114 if(!contains(e.next())) {
115 return false;
116 }
117 }
118 return true;
119 }
120
121 /**
122 * <i>(Change)</i>
123 * Adds one copy of the specified object to the Bag.
124 * <p>
125 * Since this method always increases the size of the bag, it
126 * will always return <code>true</code>.
127 *
128 * @param object the object to add
129 * @return <code>true</code>, always
130 */
131 @Override
132 public boolean add(final E object) {
133 return add(object, 1);
134 }
135
136 @Override
137 public boolean addAll(final Collection<? extends E> coll) {
138 boolean changed = false;
139 final Iterator<? extends E> i = coll.iterator();
140 while (i.hasNext()) {
141 final boolean added = add(i.next(), 1);
142 changed = changed || added;
143 }
144 return changed;
145 }
146
147 /**
148 * <i>(Change)</i>
149 * Removes the first occurrence of the given object from the bag.
150 * <p>
151 * This will also remove the object from the {@link #uniqueSet()} if the
152 * bag contains no occurrence anymore of the object after this operation.
153 *
154 * @param object the object to remove
155 * @return <code>true</code> if this call changed the collection
156 */
157 @Override
158 public boolean remove(final Object object) {
159 return remove(object, 1);
160 }
161
162 /**
163 * <i>(Change)</i>
164 * Remove all elements represented in the given collection,
165 * <b>not</b> respecting cardinality. That is, remove <i>all</i>
166 * occurrences of every object contained in the given collection.
167 *
168 * @param coll the collection to remove
169 * @return <code>true</code> if this call changed the collection
170 */
171 @Override
172 public boolean removeAll(final Collection<?> coll) {
173 if (coll != null) {
174 boolean result = false;
175 final Iterator<?> i = coll.iterator();
176 while (i.hasNext()) {
177 final Object obj = i.next();
178 final boolean changed = remove(obj, getCount(obj));
179 result = result || changed;
180 }
181 return result;
182 }
183 // let the decorated bag handle the case of null argument
184 return decorated().removeAll(null);
185 }
186
187 /**
188 * <i>(Change)</i>
189 * Remove any members of the bag that are not in the given collection,
190 * <i>not</i> respecting cardinality. That is, any object in the given
191 * collection <code>coll</code> will be retained in the bag with the same
192 * number of copies prior to this operation. All other objects will be
193 * completely removed from this bag.
194 * <p>
195 * This implementation iterates over the elements of this bag, checking
196 * each element in turn to see if it's contained in <code>coll</code>.
197 * If it's not contained, it's removed from this bag. As a consequence,
198 * it is advised to use a collection type for <code>coll</code> that provides
199 * a fast (e.g. O(1)) implementation of {@link Collection#contains(Object)}.
200 *
201 * @param coll the collection to retain
202 * @return <code>true</code> if this call changed the collection
203 */
204 @Override
205 public boolean retainAll(final Collection<?> coll) {
206 if (coll != null) {
207 boolean modified = false;
208 final Iterator<E> e = iterator();
209 while (e.hasNext()) {
210 if (!coll.contains(e.next())) {
211 e.remove();
212 modified = true;
213 }
214 }
215 return modified;
216 }
217 // let the decorated bag handle the case of null argument
218 return decorated().retainAll(null);
219 }
220
221 //-----------------------------------------------------------------------
222 // Bag interface
223 //-----------------------------------------------------------------------
224
225 /**
226 * <i>(Change)</i>
227 * Adds <code>count</code> copies of the specified object to the Bag.
228 * <p>
229 * Since this method always increases the size of the bag, it
230 * will always return <code>true</code>.
231 *
232 * @param object the object to add
233 * @param count the number of copies to add
234 * @return <code>true</code>, always
235 */
236 @Override
237 public boolean add(final E object, final int count) {
238 decorated().add(object, count);
239 return true;
240 }
241
242 }