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.collection.SynchronizedCollection;
23
24 /**
25 * Decorates another {@link Bag} to synchronize its behavior
26 * for a multithreaded environment.
27 * <p>
28 * Methods are synchronized, then forwarded to the decorated bag.
29 * Iterators must be separately synchronized around the loop.
30 * </p>
31 * <p>
32 * This class is Serializable from Commons Collections 3.1.
33 * </p>
34 *
35 * @param <E> the type of elements in this bag
36 * @since 3.0
37 */
38 public class SynchronizedBag<E> extends SynchronizedCollection<E> implements Bag<E> {
39
40 /**
41 * Synchronized Set for the Bag class.
42 */
43 final class SynchronizedBagSet extends SynchronizedCollection<E> implements Set<E> {
44 /** Serialization version */
45 private static final long serialVersionUID = 2990565892366827855L;
46
47 /**
48 * Constructs a new instance.
49 * @param set the set to decorate
50 * @param lock the lock to use, shared with the bag
51 */
52 SynchronizedBagSet(final Set<E> set, final Object lock) {
53 super(set, lock);
54 }
55 }
56
57 /** Serialization version */
58 private static final long serialVersionUID = 8084674570753837109L;
59
60 /**
61 * Factory method to create a synchronized bag.
62 *
63 * @param <E> the type of the elements in the bag
64 * @param bag the bag to decorate, must not be null
65 * @return a new synchronized Bag
66 * @throws NullPointerException if bag is null
67 * @since 4.0
68 */
69 public static <E> SynchronizedBag<E> synchronizedBag(final Bag<E> bag) {
70 return new SynchronizedBag<>(bag);
71 }
72
73 /**
74 * Constructor that wraps (not copies).
75 *
76 * @param bag the bag to decorate, must not be null
77 * @throws NullPointerException if bag is null
78 */
79 protected SynchronizedBag(final Bag<E> bag) {
80 super(bag);
81 }
82
83 /**
84 * Constructor that wraps (not copies).
85 *
86 * @param bag the bag to decorate, must not be null
87 * @param lock the lock to use, must not be null
88 * @throws NullPointerException if bag or lock is null
89 */
90 protected SynchronizedBag(final Bag<E> bag, final Object lock) {
91 super(bag, lock);
92 }
93
94 @Override
95 public boolean add(final E object, final int count) {
96 synchronized (lock) {
97 return getBag().add(object, count);
98 }
99 }
100
101 @Override
102 public boolean equals(final Object object) {
103 if (object == this) {
104 return true;
105 }
106 synchronized (lock) {
107 return getBag().equals(object);
108 }
109 }
110
111 /**
112 * Gets the bag being decorated.
113 *
114 * @return the decorated bag
115 */
116 protected Bag<E> getBag() {
117 return (Bag<E>) decorated();
118 }
119
120 @Override
121 public int getCount(final Object object) {
122 synchronized (lock) {
123 return getBag().getCount(object);
124 }
125 }
126
127 @Override
128 public int hashCode() {
129 synchronized (lock) {
130 return getBag().hashCode();
131 }
132 }
133
134 @Override
135 public boolean remove(final Object object, final int count) {
136 synchronized (lock) {
137 return getBag().remove(object, count);
138 }
139 }
140
141 @Override
142 public Set<E> uniqueSet() {
143 synchronized (lock) {
144 final Set<E> set = getBag().uniqueSet();
145 return new SynchronizedBagSet(set, lock);
146 }
147 }
148
149 }